An architecture (form and structure) that improves the efficiency of domestic water use

Material Information

An architecture (form and structure) that improves the efficiency of domestic water use
Raynolds, Mary Vera
Place of Publication:
University of Colorado Denver
Publication Date:
Physical Description:
73 leaves : illustrations ; 28 cm

Thesis/Dissertation Information

Master of Architecture
Degree Grantor:
University of Colorado Denver
Degree Divisions:
College of Architecture and Planning, CU Denver
Degree Disciplines:
Committee Chair:
Vlahos, Ekaterini
Committee Members:
Morris, Eric
Bressler, Gene
Holleran, Michael


Subjects / Keywords:
Water efficiency ( lcsh )
Architecture, Domestic ( lcsh )
Landscape architecture in water conservation ( lcsh )
Architecture, Domestic ( fast )
Landscape architecture in water conservation ( fast )
Water efficiency ( fast )
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )


Includes bibliographical references (leaves 68-72).
General Note:
College of Architecture and Planning
Statement of Responsibility:
by Mary Vera Raynolds.

Record Information

Source Institution:
University of Colorado Denver
Holding Location:
Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
61503088 ( OCLC )
LD1190.A72 2005m R39 ( lcc )

Full Text
An Architecture (Form and Structure)
that Improves the Efficiency of Domestic
Water Use
Mary V. Raynolds

Mary Raynolds
B.A., Wellesley College 1974
M.A., Princeton University 1978
Ph.D., Harvard University 1983
A thesis submitted to the
University of Colorado at Denver and Health Sciences Center
in partial fulfillment of the requirements for the
degree of
Master of Architecture, College of Architecture and Planning

This thesis for the Master of Architecture degree has been approved by:

Chapter 1: Introduction 4
Overuse and misuse of water is an old story 6
Chapter 2: Sources and distribution of water resources in Colorado 7
Water sources in Colorado 8
Water issues in Colorado 15
Water issues in Weld County 19
Chapter 3: A water resource responsive approach to design 21
Need for a sustainable approach to design 21
Domestic water use 21
Dwelling density and water use 23
Comparison of agricultural and domestic water use 25
Chapter 4: Strategies and patterns for water sensitive design 26
Large scale approaches to design 27
Open space development 28
Storm water management 31
Mid-scale approaches to design 32
Clustering houses 32
Slope gradients for water flow 34
Engineered wetlands 33
Low water use landscaping 35
Small scale approaches to design 36
Capture 36
House orientation based on storm direction 36
Roof slope and orientation 36
Roof materiality 38
Patios 38
Storage 40
Cisterns 40
Ephemeral water feature in patio 42
Snow corrals 43

Water efficient plumbing fixtures 44
Outflow 44
Engineered wetlands 44
Greywater systems 45
Chapter 5: Case Study 45
Site and site issues 45
Location 45
Annual climate 48
Housing density 50
Topography and housing placement 50
Summary of site conditions 54
Prototype house 54
Water capture 55
Water storage 58
Water outflow 59
Other issues in sustainability 61
Chapter 6: Water use and sustainability 65
References 68

Our mythic visions of the West, whether of cowboys, Native Americans, miners,
Spanish colonists or homesteaders, have long drawn visitors and immigrants to the
fragile, beautiful lands between the high Plains and the Pacific Ocean. The landscapes of
the West often symbolize America to us, and especially to citizens of countries in Europe
and Asia. The deserts, mountains and broad valleys seem full of freedom and limitless
possibilities, but our very presence is changing much of the West permanently.
The West is no longer as it appeared in Bonanza, or in promotional literature of
the Union Pacific or Santa Fe Railroads, or in the countless Westerns with which the last
several generations of movie viewers grew up. The West is now as urban as most other
parts of the continental United States, as 86% of Westerners live in cities (1). The interior
West grew faster than any other region of the United States in the 1970s, 1980s and
1990s. Ten of the fifty fastest growing counties in the country during the 1990s were in
Colorado; the fastest growing county in all the United States for at least five years was
Douglas County, part of the metropolitan Denver area (1). As population in the interior
West booms, problems associated with urbanization have appeared: polluted air and
water, heavy traffic, sprawl, loss of traditional work in rural towns, erosion of topsoil and
habitat, displacement of long time residents as land values soar, crowds in formerly
isolated areas.
Although we still act as though the land, air, water, mineral, animal, and plant
resources of the West are abundant and limitless, as they were perceived in the 19th
century, we are rapidly exhausting many aspects of the natural world that surrounds us.
Of these resources, water is one critical to life (Figure 1). Western water disputes are an
old story, almost as old as European settlement, but access to adequate water remains
crucial for Western residents. We cannot continue to expand into the countryside by
assuming that money will cure all water problems, that there will always be a willing
seller if the price is high enough. This is as naive as the 19th century belief that rain
follows the plow, and potentially as destructive.

Natural resources in the West
Breatheable air
Figure 1. Water is a crucial natural resource which may become
limited and therefore limiting as the population of the west grows

The possible ways to tackle Western water issues are complex, and include addressing
public water policy, public attitudes towards private property rights, water law, landscape
aesthetics, and assumptions about the virtue of growth and continued
building as an economic engine ensuring prosperity. True sustainability in terms of water
use will probably not be possible as long as population growth continues unchecked, but
many areas could move towards self-sufficiency with some changes in water use patterns.
Those of us who design the built environment, planners, landscape architects, and
architects, can influence the ways in which water resources are used, whether wisely or in
a profligate manner. The purpose of this thesis is to examine several design strategies in
which the architecture, the built form, of residences may be used to move towards water
self-sufficiency and to contribute to the long term goal of using Western resources in a
sustainable way.
Over use and misuse of water resources is an old story:
Inappropriate use of water has plagued human civilization for thousands of years.
Irrigation systems in hot, arid climates deposited salts in fields, eventually limiting local
food production. Human induced high salt content of water supplies is believed to have
caused the demise of the Harappan civilization in the Indus Valley and the Nasca Plain
civilization in what is now Peru(2-4). The beautiful city of Fatehpur Sikri, built by Shah
Jalal-ud-din Mohammed Akbar west of Agra, had to be abandoned within one generation
as water wells dried up (5, 6). Disputes over increasingly scarce water resources may
have contributed to the evacuation of the Anasazi peoples from the Four Corners area in
the 13th century, as the region suffered through multidecadal drought(7-9).
Access to adequate potable water supplies is a worldwide problem(10, 11).
Although those of us who live in affluence in the United States assume that money and
technology will allow us to continue to grow, to build new houses, schools, commercial
buildings, factories and all the other structures in which we conduct our lives whenever
and where ever we choose, and that the resources, especially water supplies, will appear
to support our ever expanding population, the reality in many areas of the country is that
we are within decades of exhausting essential resources, particularly water resources.
This thesis, in proposing techniques for using those water resources now available
in more efficient ways, offers some temporary solutions to the impending water crisis in

the West. Although many of the design strategies are directed at water, the residential
design does address some larger issues of sustainability: use of local, renewable materials
for building, orientation to take advantage of solar heat and light, use of native plants in
landscaping. Water is but one of many resources that will become scarce in the next
quarter century, as the Front Range may absorb an additional 2 million individuals. The
decisions we make in the next very few years will dictate how we will live then: how
much and where open space will be (if there is any), where roads and sprawl will be, how
many Walmarts and strip malls will line our major highways and commuting arteries.
The choices we make will not only have an impact on our visual world, but will also
affect the quality and availability of resources we now take for granted.
History tells us that earlier civilizations have declined because they did not learn
to live in harmony with the land. Our successes in space and our triumphs of technology
hold a hidden danger: as modem man increasingly arrogates to himself dominion over the
physical environment, there is a risk that his false pride will cause him to take the
resources of the earth for granted-and to lose all reverence for the land (12).
As we enter the twenty-first century, a global water crisis is threatening the
security, stability and environmental sustainability of all nations...(13)
The purpose of this work is to propose several design strategies for buildings that
approach self-sufficiency. Although the case study focuses on residential design,
components of water sensitive design approaches could easily be applied to any type of
building: commercial, office, or school.
Water resources in Colorado:
The high plains and intermountain West, the territory west of the 100th meridian,
is a high desert, as first noted by John Wesley Powell in the years immediately after the
Civil War. Powell explored the west in 1867-1868 and returned to make his famous trip
down the Colorado River in 1869. He compiled data on the geology, climatology,
hydrology and ecology of the arid lands west of the 100th meridian, including the Rocky

Mountain region (12, 14, 15). Powell early realized that water resources in these arid
lands were critical and limiting, and he proposed in his 1879 Report on the Lands of the
Arid Region a comprehensive plan for land use, irrigation systems, and water law (15).
As there was not enough water to go around, he proposed that it be shared equitably (12,
15). Powell recognized that land alone in the West was almost worthless; only the
application of water gave value to land, and therefore rights to water resources should be
irrevocably tied to the land by law. Powell proposed surveying and organizing lands
according to drainage basins, not solely by the orthogonal Jeffersonian system of land
platting in order to best utilize scarce water resources (12, 15). The post World War II
boom in Western population resulted in value accruing to open land near urbanizing areas
as a result of development pressure, but in recent years Powells observation that land
only has value if watered has again become prophetic as municipalities struggle to
provide water to their growing populations.
Colorados water is at the nexus of the impending regional western water crisis, as
the state boundary encompasses the headwaters of seven major rivers: the Colorado, the
Arkansas, the South and North Platte, the San Juan, the Rio Grande and the
Yampa/White (Figure 2). These rivers not only supply water to agriculture and cities
within Colorado, but also serve as major suppliers of water to downstream states. This is
especially true for the Colorado River, which provides water to Arizona and California.
As populations increase in both the downstream states and the headwaters states,
conflicts over the distribution of Colorado River water have rekindled over and over.
Population growth in Nebraska and Kansas has created similar disputes regarding water
in the Platte and Arkansas Rivers.
Water sources in Colorado:
Water supplies in Colorado come from two sources: surface water and
groundwater (Figure 3). Surface water is meteoric water: water that comes from rain and
snow and enters streams, rivers, ponds and lakes. Groundwater is water trapped in rocks,
usually sandstones (sand sized grains) or conglomerates (gravel sized grains).
Groundwater in rocks is present as a thin film surrounding the grains, not as open or
flowing bodies of water(16), and is obtained through wells.

Figure 2. The state of Colorado encompasses the headwaters
of seven major rivers.
Sources of water in Colorado
Figure 3. Water resources in Colorado come from either surface water or
from groundwater

Average stream flow
.Wftwia' j* TT E
(W>*ar fmo* T#arr
Figure 4. People are where water
isn't in Colorado
Population density by county
Dansny of County
(Numtier of residents
par square rrafaof
| 100 499
| 500-999
SCALE 1 4.000.000
From Ground Water Adas of Colorado
Figure 5. Transbasin diversions of water: acquisition of
Western Slope water for use east of the Continental Divide

Colorado receives, in a year with average snow and rainfall, about 93 million acre feet of
precipitation per year, of which only 10-15 million acre feet enter streams and rivers (17).
(An acre-foot is approximately 326,000 gallons.) However, the amount of precipitation
per year is highly variable in Colorado, and indeed in much of what Powell termed the
arid lands. Large excursions in annual precipitation are usual, as data on quantities of
historic and prehistoric precipitation have shown (9, 18, 19). Cycles of drought have
alternated with cycles of abundant rain and snowfall for more than 1500 years(9). In fact,
Colorado received above average levels of annual precipitation during the twenty-five
year period between the mid-1970s and the late 1990s, during which the states
population grew rapidly. Many residents became acclimatized to (relatively) abundant
and inexpensive water supplies, and the drought conditions that began in 1999 were only
slowly recognized. The variability in annual water availability leads to problems for users
and for water planners, especially in districts with rapidly increasing populations.
The distribution of surface water resources across Colorado is location dependent,
as average stream flows vary with the patterns of precipitation (Figure 4). Stream flows
are higher west of the continental divide than east of the divide as annual precipitation,
mostly in the form of snow, is higher. However, population densities in the east are far
higher than in the western part of the state, and average precipitation is lower, so the
people are living just where the water is not (Figure 4) (17, 20). Higher water demand,
therefore, is geographically displaced from more abundant surface water supplies. The
inequality of supply and demand has led to the large transmontane diversion projects that
diver water from western drainages, primarily the Colorado River drainage, to eastern
drainages. Water derived from diversions from watersheds west of the Continental Divide
is classified as foreign water. The largest of these diversions is the Colorado Big
Thompson project (C-BT) that moves water from the Willow Creek and Windy Gap
reservoirs near Granby through the Adams tunnel into Horsetooth, Flatiron and Carter
Lake reservoirs in the northern Front Range (Figure 5). The C-BT project was developed
by the Bureau of Reclamation in 1937 to provide (cheap) irrigation water for farmers east
of the mountains(17, 21). However, municipalities in the northern Front Range urban
corridor now use more than half of C-BT water. The Windy Gap reservoir was developed
in the Colorado River drainage in 1968-1985 to augment C-BT water (17, 22).

Denver, Aurora, Colorado Springs, Fort Collins, and Greeley derive a substantial
portion of municipal water from transmontane diversions. Denver Water receives surface
water collected west of the Continental Divide and stored in a series of reservoirs,
including Dillon, through the Roberts and Moffat tunnels. Colorado Springs receives
water from the upper Arkansas drainage through a series of tunnels and reservoirs
including Hoosier Pass, Homestake, Bourstead and Twin Lakes. Aurora receives water
through the same upper Arkansas sources as Colorado Springs. Greeley, Loveland, and
Fort Collins rely on the Colorado-Big Thompson diversions through the Adams Tunnel
for much of their foreign or transbasin water (Figure 5) (22-24).
Cities in the Front Range also rely on native water, or water used in the basin of
origin(17). In Division 1, which includes Denver and cities north to the Wyoming border,
native water consists of water from the South Platte and its tributaries such as the Big
Thompson River. Native water is subject to prior appropriation laws, in which water
rights are allocated according to the time of first use. Older or more senior rights have
priority over junior rights, but the use is usually subject to requirements for maintaining
adequate supplies for downstream water rights. In contrast, water diverted from other
basins is considered foreign, belongs entirely to the diverter, is not subject to prior
appropriations and therefore can be used to extinction (17). It is sometimes in the best
interests of municipalities to maximize foreign water consumption, as there are fewer
restrictions on its use.
Therefore, surface water supplies for cities along the Front Range in Division 1
are a complex composite of water derived from the South Platte and its tributaries, and
water from basins west of the Continental Divide, predominately from the Colorado
River Basin. Figure 6 illustrates the distribution of foreign and native surface water used
by the larger communities in the Front Range.

% foreign
% native
Figure 6. Relative use of 'foreign' (diverted) water and 'native'
water (basin of origin) by Front Range municipalities.
Colocdo-Big Thortipopr, 'C-BTl Shares Owrwd 1957 1999
1IHI A.g
Ml --------------------

5 140 ;
|n- j


Figure 7. In 1996, the number of CBT water shares
held by agricultural interests were fewer than those
held by municipal interests for the first time. The trend
towards increased municipal use of CBT water continues.

At present, about 78% of all water used by Coloradoans is surface water; 22% is
groundwater. Most of the groundwater used by consumers in the Front Range is ancient
water, estimated to be 8,000 to 30,000 years old (25). Although the aquifers containing
the groundwater are being recharged by rain and snow on the surface, the recharge rate is
extremely slow. Therefore, groundwater is effectively a non-renewable resource that is
being mined, in some parts of the state to extinction(17, 20). Although most densely
populated regions east of the Continental Divide use surface water as the dominant
source of water, the rapidly growing communities and unincorporated subdivisions in
Douglas and Elbert counties rely heavily on groundwater.
Depletion of deep source groundwater in these counties is location dependent, as
there is more water in the deeper parts of the aquifers, but in some areas residential wells
are already drying up. Recently, the Douglas County Commissioners denied developers
permits to build a 2000 home golf-course residential project in an area of the County in
which groundwater resources are known to be exhausted. The water resources for
municipalities and unincorporated subdivisions that rely on groundwater for domestic
water supplies will be limited in the future. As most all the surface water is already
allocated, these communities will have difficulties in replacing groundwater with surface
water sources. The price of replacement water may become high; it is fortunate for the
residents of Douglas County that they are the most affluent on average in the state.
The percentage of water used by different groups in Colorado has been shifting
for the last several decades. At present, 85-90% of all water consumed in Colorado is for
agricultural purposes (17, 20). The amount of water used by agriculture has been
declining in the last 25-30 years, but still represents the largest use by volume in the
state(26). For example, the Colorado-Big Thompson project was developed by the
Bureau of Reclamation to provide water for agriculture east of the mountain front. As
cities grew and bought CBT shares to augment municipal water, the ratio of agricultural
to municipal deliveries decreased. In 1996, the amount of CBT water shares owned by
agricultural interests and cities were equal for the first time; in the last 9 years the number
of shares owned by cities (or developers) has continued to increase (Figure 7). Municipal
and industrial users, which include residential users, directly consume about 15% of
water used annually in the state; this percentage does not represent total municipal water

use, however, as about 25% of all water is diverted into storage each year. Municipalities
are significant users of stored water so that the total amount of water consumed by cities
and towns exceeds 15% annually (27).
Water issues in Colorado
The recent drought has refocused attention on the state of water supplies for the
rapidly urbanizing Front Range. As the population in the west becomes increasingly
urban(17, 28), the need for water in metropolitan areas will continue to grow. It has been
estimated that by 2030, when the population of Colorado is expected to be approximately
7 million people, or about 3 million more people than now live in the state (Figure 8) (17,
29), an additional 630,000 acre-ft of water will be needed to support municipal and
industrial use (30). Most of the available surface water is already allocated, so the
source(s) for additional water needed to support growth is problematic. Indeed, expansion
of several resort communities in the western region of Colorado has been hampered by
lack of water (31).
In Colorado, the competition for water use between municipalities of the Front
Range corridor, agricultural operations in the eastern plains and in the western mountains,
and ranching, farming and resort towns in the western mountains, has caused acrimonious
debate for more than a decade. There is little unallocated surface water available for
municipalities on either the eastern or western slope; therefore, most of the new surface
water supplies will come from reallocation of existing surface water rights (30, 32).
Agriculture uses 85-91% of all water in Colorado (17, 20, 30), and transfers of water
rights from agricultural users to municipalities will continue by necessity. (A 10%
decrease in agricultural water use would increase water available to municipalities by

Population growth in Colorado 2005-2030
7000000 -]
6000000 -
5000000 - entire state
Front Range
4000000 - a Den-Boul
3000000 - A V X x Denver Met
A X x West Slope
2000000 - A X X East plains
1000000 -
0 - X X X X X 1 1 1 i r T* r I
1990 1995 2000 2005 2010 2015 2020 2025 2030
Figure 8. The problem of people needing water in the Front Range
is only going to get worse
Or- >s-'- J'l -.'i
Figure 9. Agricultural to municipal water transfers Division 1
from 1975-1995.

gap water demand and supply
Water supply and demand 2005 and 2030
250 -i
150 -
supply demand
Figure 10. A 20% gap between supply and demand is
expected by water providers by the year 2030.
From Barry, H (33)

The number of shares transferred from agricultural to non-agricultural water use is
illustrated in Figure 9 for Division 1, the South Platte drainage. Similar transfers from
agricultural to municipal use have also occurred extensively in the Arkansas drainage
(Division 2). As new transmontane diversion projects are likely to prove prohibitively
expensive in the absence of federal subsidies, purchase of agricultural water rights is the
most cost effective and efficient mechanism for Front Range municipalities to increase
their water supplies (33). As municipal water providers plan for future growth, many
predict that there will be a 20% gap between available water supplies and demand in 25
years if new supplies are not identified (Figure 10), further pressuring agricultural water
resources (33-35).
Agriculture production was worth over $5 billion to the state of Colorado in 2003,
up from $3 billion in 2001(17, 36), but this represents only about 1-2% of the total
contributions to the state economy (36). The decreasing role of agriculture, farming and
ranching, as one of the major economic contributors in the state has increased pressure on
reallocation of agricultural water. In addition, the value of water for municipal use is
orders of magnitude greater than for agricultural use(17, 37). In 2001-2002, rights to
irrigation water close to the Nebraska border were worth about $500/ acre-ft whereas an
acre-ft of Colorado-Big Thompson water was worth about $20,000 (17, 37). The large
differential between the values of agricultural and municipal water rights stimulates
transfer of agricultural water rights for non-agricultural uses.
The effects of loss of water rights on rural areas include loss of open land and
subsequent loss of habitat, especially in riparian areas, decreased value of dry land
compared to irrigated crops, decreased agricultural equipment and other retail sales in the
immediate area, (17, 28, 29, 32, 38, 39). However dire the local effects of water loss,
transfer of water rights to municipal use tends to benefit the metropolitan area acquiring
the rights (39). The overall benefit to the state economy exceeds the negative local impact
of water loss.
The negative effects on the local economy, the loss in personal income to those
farmers who have sold water rights, and the loss of agricultural sector jobs have been
detailed, but the long-term impact of permanent water rights transfer on the fate of
agricultural land in Colorado has not been studied as thoroughly (28, 29, 38, 39). Many

farmers assume, especially farmers with landholdings near urbanizing areas, that their
land is intrinsically worth a substantial amount for commercial, industrial or residential
development. However, after farmers have sold their water rights, it is also possible that
the value of their land is diminished, especially if there are no alternative sources of
Water issues in Weld County:
Weld County is the site for the case study described in detail in Chapter 4. Weld
County was chosen for several reasons: first, it is a county in which there is a rapid
conversion of farmland for residential development in the urbanizing corridor around
Greeley, the County Seat. Second, the agricultural water rights available consist of both
surface and groundwater rights. Third, the County does not yet have a consistent,
comprehensive open space policy, agricultural land protection policy, or water supply
strategy implemented; therefore, open space planning is up to individual landowners or
developers. In the absence of county or citywide water planning, it is even more crucial
for individual residences to use water as efficiently as possible.
Western Weld county is rapidly urbanizing, especially the part of the county
between Greeley and the interstate 25 corridor. The blossoming formerly agricultural
communities surrounding Greeley, and the unincorporated subdivisions, are bedroom
communities for Greeley, home no longer to just agriculturally based companies such as
ConAgra, but also to high tech companies like Hewlett Packard and an expanding
regional healthcare industry managed by Banner Healthcare. The residents of the
subdivisions ringing the old part of Greeley also work in Loveland, Longmont, Fort
Collins and the Denver metropolitan area.
The city of Greeley and the surrounding agricultural areas receive most of their
water supply from surface water, but some of the agricultural land uses groundwater from
both shallow and deep sources. The city of Greeley has a long term water plan in place;
the city expects that it has enough water to service the needs of its citizens and businesses
through 2050 if the population growth does not exceed the predicted rate of increase (40).
The towns of Milliken and Evans, flanking Greeley to the southwest and southeast
respectively, were once small farming communities, and are now expanding suburban

Greeley has access to 42,500 acre-feet per year; as of 2004 the yearly demand was
26,000 acre-feet per year and is expected to increase to over 39,000 acre-feet by
2050(40). The city supplies water to Evans and to Milliken in addition to its own
residents (40-42), and as the greater Greeley metropolitan area grows, the city will have
to pursue additional water sources. The city plans to increase its share of water from the
Greeley-Loveland canal as it buys agricultural water rights (40). If the growth rate of
Evans and Milliken exceed expectations, as is possible given the aggressive approach of
these communities to incorporating distal farm and ranch lands, surface water supplies
may become problematic well before 2050.
Greeley is not the only community seeking to buy agricultural water rights from
farmers in Weld County. Developers in the Denver metropolitan area also consider Weld
County water rights ripe for the taking, as suggested by a recent news items(43). At least
one developer has purchased a large parcel of land near Milliken for the purpose of
physically removing the agricultural water for use in a suburban development closer to
Denver. The water in this case is shallow groundwater recharged by the Big Thompson
and Platte Rivers, and it remains to be seen what removal of the groundwater will do to
local availability of water from the shallow aquifer and to the hydrological cycle.
Another aspect of agricultural water use that will affect the hydrological cycle of
Front Range streams and rivers as agricultural water rights are transferred is the nature of
return flow through field irrigation. Irrigation water applied to fields returns to surface
flow slowly; irrigation of agricultural lands east of the mountain front has altered the
annual patterns of flow in the South Platte and its numerous tributaries that are used as
water sources, changing the river and streams from sporadic, seasonal flows to year
round continuous flows. It is estimated that agriculture allows water in the South Platte
and other Front Range drainages to be used seven times before leaving Colorado(44); in
the absence of using fields as temporary water storage devices, surface water sources may
return to sporadic, seasonal flow. Subdivisions contain significantly more hard surfaces
than the same area of tilled ground, which is likely to result in a profound change in
subsurface water saturation and slow return flow to surface streams and rivers.
In the future the burgeoning area surrounding Greeley is likely to continue to
come into conflict with competing interests for agricultural water rights needed to sustain

growth. Both agricultural to municipal water transfers and water conservation by users
are necessary to provide adequate water supplies. This fundamental shift in the ways in
which water is used in the state has implications for water suppliers and domestic water
users, and may profoundly alter the types of agricultural crops grown in Colorado.
Need for a sustainable approach to design:
In the coming decades many of the rapidly growing areas in Colorado, especially
communities in the comparatively arid area east of the mountains, will face difficulties in
obtaining new water sources. Although most water is used at present for agricultural
purposes, and therefore agricultural to municipal transfers should provide water for future
residential needs, it remains to be determined how feasible large scale redistribution of
water from agriculture to domestic use will be in future (17, 28, 45). Much of the easily
reallocated water has already been transferred, and accessible agricultural water rights on
the eastern slope may be needed as agricultural land is turned into subdivisions.
Although agriculture continues to use most of the water in Colorado, domestic
water use continues to expand quickly, and enhanced efficiencies in residential water use
can only preserve water resources that are increasingly limited.
Domestic water use:
Statewide, the average amount of water used per person is 204-208 gallons per
day(26, 46, 47); the average use in the Denver Water district is somewhat lower, about
190 gallons/person/day (47). The total water use in a typical single family home is about
half an acre-foot per year, or 163.000 gallons(47). Daily water use per person in Colorado
is higher than that in many other parts of the arid West; for example, the average daily
use per person in Phoenix is about 140 gallons, and is higher than the national average of
179 gallons/person/day(26).
Municipal water systems service homes, industries and businesses; usually
residential water consumption is greater than that of other users. Denver Water reports
that 48% of water used is by single-family homes, 21% by businesses and industry, 17%

by multifamily dwellings, 9% by public agencies (includes fire hydrants) and 6%
unaccounted (usually system leakage or loss) (Figure 11) (47).
water use in Denver
single family
public agency
system loss
Figure 11. Denver Water: distribution of water use
domestic water use
Figure 12. Typical distribution of water use by
single family households. Average water use in Colorado
Is 204-208 gallons per person per day.

In houses, water use is distributed between bathroom (toilets, showers, tubs),
laundry, cooking, drinking and landscape watering. Of these, landscape watering
comprises between 50 and 65% of total water use depending on the season, 30% of water
is used in bathrooms, and 10 to 15% in dishwashers and laundry facilities (Figure 12)
(26, 47). Decreasing domestic water use, especially by conserving water used for
landscaping and in the bathroom, will have a large impact on most municipal water
districts, as it is common for single-family residences to use close to half of all water and
for all residential use (including multifamily dwellings) to approach three-quarters of all
water consumed. Further, if single-family residences could incorporate features that made
them at least in part water self-sufficient, the strain on water supply and delivery systems
could be significantly diminished.
Dwelling density and water use:
The amount of water used by households is a function of the density of dwelling
units per acre, and data on water use as a function of dwelling density have been
compiled for communities in Colorado including Greeley, Denver and Boulder (47-49).
In Greeley, low-density residential areas, defined as 3.5 units/acre, use 2.4 acre-
feet/acre/year. Moderate density areas, 6 units/acre, use 2.8 acre-feet/acre/yr and high-
density areas, 18 units/acre, use 4 acre-feet/acre/year (Figure 13)(48). In comparison,
urban high-density areas with 100 units/acre use 19.5 acre-feet/acre/yr and with 500
units/acre use 95.7 acre-feet/acre/yr (Figure 13)(50). If these water used data are recast as
annual use per household (hh; or use per unit), the low density Greeley household would
use 0.68 acre-feet/yr, the moderate density household would use 0.46 acre-feet/yr, the
high density Greeley example would use 0.22 acre-feet/hh/yr; and the urban examples,
data from San Francisco, would use 0.195 acre-feet/hh/yr (Figure 14). It is clear that
increasing dwelling density reduces water use per household.

water use in acre feet/year water use in acre feet/year
Dwellings and water use-the benefits of density
120 -|
100 -
80 -
60 -
40 -
20 -
6 18 100
dwelling units per acre
Figure 13. Water use in acre-feet per acre
Dwellings and water use-the benefits of density
3.5 6 18 100 500
dwelling units per acre
Figure 14. Water use in acre-feet per dwelling unit or household

Increased density of dwellings decreases water use primarily by lessening the amount of
landscaping and therefore outdoor watering. Cluster, conservation, or open space
developments, described in detail below, allow developers a set number of units per acre,
but mandate that a sizeable fraction, usually 50%, of the land remain open. This results in
close packing of the residential units, thereby decreasing lot size and possibility of water
intensive landscaping, even in suburban settings where the standard dwelling density is
one house or less per acre.
Comparison of agricultural and domestic water use:
In the future, most of the new sources of surface water for municipal use are
likely come from transferred agricultural water rights, as the surface water supply in
Colorado is over allocated and groundwater resources are limited, fragile and overused
(17,20, 30,32).
Although it is assumed that transfer of water rights from agricultural to municipal
use will result in greater water use efficiency, this may not necessarily be true. A study by
the California Department of Water Resources showed that water applied to single-family
residences in San Joaquin valley was 2-3 acre-feet/acre. Agricultural water use in the
same area ranged from 1-5 acre-feet/acre. Residential water use was similar to water
needs for some fairly thirsty crops, including grapes, tomatoes, com, almonds/pistachios
and other truck vegetables(38).
How do agricultural and domestic water use
per acre compare?
O 4
3.5 DU 6 DU 18 DU av CO farm truck farm
water consumption per acre houses vs farms
Figure 15. Comparison between agricultural and domestic
water consumDtion 25

In Colorado, the average agricultural water use per acre is close to 1 acre-
foot/acre (51), and the average use per household is about 2 acre-feet/acre in Denver
(average density 4 units/acre) (47) and in the suburban areas around Greeley is about 2.4
acre-feet/acre for low density developments(48). Low-density development is the most
wasteful of water resources, and has the highest per household water consumption (see
discussion above). Low-density development, 3.5 houses per acre or less, uses more
water per acre than the average agricultural crop (Figure 15). Although high-density
development uses more water per acre than agriculture, per household consumption is
much less than low-density development. Furthermore, high-density development does
not consume land at the same rate as low-density development(52); therefore, low-
density development on agricultural land, in which entire agricultural parcels are
converted to subdivisions, increases water use per acre compared with agriculture.
Transfer of the water rights from agricultural lands to municipalities as the farmlands are
developed may not be sufficient to supply the additional water needed per acre for
domestic consumption.
As the population of Colorado more than doubles in the next 25 years, obtaining
access to adequate water resources will become increasingly difficult for municipalities
as they grow. Reassessing the ways in which domestic water is used, and using design to
improve building sustainability, especially approaches to water self-sufficiency, will
delay the eventual crisis. But, similar to oil, there is finite water available in the West and
at some point the ability of water resources to sustain an ever-growing Western
population will be exhausted. It is in everyones best interest to begin to work towards
regional and not solely local approaches to obtaining and maintaining adequate water
Design choices at all scales affect utilization of water resources, from platting
subdivisions (dwelling density), to selection of plants for landscaping, to picking roof
slope and roofing materials. The architecture, the physical structure of houses and other

built site components, can be used at minimum to direct water through the site. In a more
aggressive approach to water acquisition, the architecture may also be used as part of an
integrated system to capture, store and deliver water where needed. Using architecture to
move towards individual self-reliance for water could contribute in the long-term to
enhanced local and regional sustainability in Colorado.
There are many possible approaches in developing an architecture that responds
to water scarcity, including both technical and design components. Large, medium and
small-scale strategies can all contribute to designs that have efficient water use and water
conservation as a primary objective.
Large-scale approaches to design:
Subdivisions begin with large scale planning, and city and county zoning policies
dictate the density and distribution of houses within the development. The standard
method of laying out subdivisions maximizes division of the developable land into
individual parcels with no open space except for wetland areas, steep slopes, or storm
water management basins (53). From a water management perspective, replacement of
farmland by typical suburban development of four to five houses per acre alters the
natural flow of water from precipitation through the site, as porous cultivated soil is
replaced by the hardscapes of streets, driveways and roofs. This change can lead to
flooding after a rain-storm or during spring snowmelt, and can change the way that water
is absorbed and flows through the subsurface (44).
Lower-density development of agricultural lands also presents problems for the
surrounding communities or host-county. Although the issues with increased coverage of
the land with hard surfaces are less severe, there remain changes in the ways water moves
through farmette or ranchette development, as the acreage is no longer farmed. Parcel
sizes of five to 40 acres per single residence are too big to mow and too small to plow,
so, although there is more open space than in a higher density subdivision, there is a
similar net loss of useable open space in low-density development (52). Percolation of
water through the soil and return of water to the watershed via subsurface flow alter, as
the soil is no longer tilled (44). From a water cycle perspective, low-density development
may only be slightly better than high-density development. A significant disadvantage of
low compared to high (5 dwellings per acre or more) density development is that much

more water is likely to be poured on landscaping, increasing the net water use per
household in the low density development.
There are alternative ways of approaching subdivision design that retain the same
number of residential units or increase the number of units while providing more
common space, either as open space or as neighborhood shopping/gathering areas. These
have the added benefit that storm water can be managed in a more holistic or natural
way, preserving as much as possible the local water table.
Open Space development:
Open space development, cluster development or conservation development
zoning mandates that a substantial percentage of the parcel to be divided remain open
(53). This development method has the advantage of retaining a large proportion of the
land as open space that can continue to be farmed and/or grazed, or turned into wildlife
refuges, hiking/biking preserves, or other outdoor spaces for the homeowners; many
conservation developments in rural/suburban interfaces or in sensitive ecosystems reserve
50% or more of the land (53). In order to remain an attractive alternative development
scheme to those selling the land and to entice developers to build such subdivisions,
conservation developments allow the same total number of units to be built, but the units
must be clustered and sited on much smaller parcels than would be the case if all of the
land were platted for houses. Roads are singly loaded, in that houses are built on one side
only, giving all houses frontage onto the preserved open spaces (Figure 16).
Cluster or open space developments are cheaper to build in that there are fewer
and shorter interior roadways, driveway lengths are also shortened, and sewer lines,
electric lines and other services are similarly more accessible. Clustering houses makes
storm water management easier, and allows for alternatives to storm sewers (54). Thus,
from a cost perspective, open space developments decrease developers costs, and often
increase the value of the new homes, as analyses have shown (53).
There are a growing number of developments incorporating densely clustered
houses surrounded by commonly held undeveloped land. These include Pingry Park
development north and west of Fort Collins, Jackson Meadows development near St.
Croix, Minnesota, and Civano near Tucson Arizona.

Figure 16. Cluster/open space/conservation developments minimize infrastructure,
maximize density, improve storm water management, and maintain open
space for agriculture, recreational trails, wildlife habitat.

Jackson Meadows development near St. Croix, close to Minneapolis-St. Paul, combines
open space planning with alternative wastewater disposal, so is a particularly good
precedent for water responsive development in the Front Range. Jackson Meadows was a
working farm until the mid 1990s, when the owner decided to retire, sell his land, and
move to Arizona, a theme common to farmland development in Colorado. The original
developer proposed a standard subdivision, in which all of the land would be converted to
lots, streets, and sidewalks. Local residents proposed an alternative in which a
considerable portion of the land would be maintained as meadows and woodlands, as
they were concerned about the effects of a standard subdivision on the visual quality of
their town. The initial developer dropped the project, and the townspeople were able to
work with another developer and the landowner to determine a plan that would work for
all. Jackson Meadows follows the guidelines of new urbanism: high-density
development, houses close to front lot line (or street), garages in back, with the addition
of a significant amount of common open space, as a little more than 50% of the original
farm remains undeveloped in perpetuity. Rather than put separate septic leach fields
behind each house, which would have dictated against high-density development, the
developers chose to use an engineered wetlands for wastewater treatment. This allowed
homes to be built close together; in addition, the wetlands provided habitat for many
species of birds and mammals, thus adding an amenity for many living in the
development (55).
Cluster/open space/conservation development is the most attractive alternative
approach for water-responsive residential development in the arid plains east of the Front
Range. From a water conservation perspective, smaller, denser residential parcels can
decrease water use by limiting the surface area devoted to landscaping. Further, retaining
half or more of the parcel in agricultural use would preserve the subsurface return flow of
water to the watershed that occurs in irrigated areas. Houses would be clustered to take
advantage of natural water movement across the land, in order to modulate storm water
runoff, to replace exogenous water for landscape maintenance, and to provide naturally
and seasonally green areas near the homes. In the site shown in Figure 16, houses have
been clustered to take advantage of drainage patterns across the site (direction of water
movement shown as blue arrows in blue fields). Such areas tend to remain moist longer,

hence be greener than the surroundings. Grading of home sites during construction could
enhance the natural drainage patterns, drawing water around the houses in such a way as
to provide water for appropriate plants (drought tolerant, preferably native). This would
result in narrow greener belts around the houses, providing visual relief.
Storm water management:
It is ironic that in an arid area like the high plains of Colorado too much water can
be a problem. As agricultural lands become subdivisions, disposing of rainwater and
snowmelt becomes difficult. Storm water management in traditional subdivisions that
contain many hard surfaces, roofs, sidewalks, paved roads, is necessary due to heavy
flows of polluted rain water or snowmelt into storm sewers after a storm (56). Storm
sewers and the excess capacity required in sewage treatment plants required to handle
unusually wet storms is expensive for municipalities and failure of these systems can lead
to contamination of surface waters. Thus, eliminating the need for storm sewers decreases
the cost of the infrastructure necessary in a new development and the ongoing costs of
water treatment facilities. There are several strategies for reducing on-site storm runoff
while allowing precipitation to percolate through the soil, which maintains natural soil
water content and allows many rivers and streams to flow year round. One option is the
vegetated swale, which directs runoff from houses and streets through plant covered
depressions. Another is to use porous pavers in roads and in driveways, to minimize hard
surfaces, while allowing rainwater and snowmelt to absorb through the roadways.
Cluster developments that manage storm water runoff without excessive reliance
on standard storm sewers and costly treatment infrastructures, including the Woodlands
north of Houston Texas, are cheaper to build and cheaper to operate in terms of water
treatment infrastructure and operational costs compared to standard subdivisions (54).
The Woodlands clusters homes in higher areas, preserving the natural drainages and
flood plains as open space and parks, which still serve as water channels after storms. In
addition, lot line and roadside swales also allows water from small storms to absorb into
the soil. These strategies saved $14 million on the cost of the initial development, while
preserving thousands of trees, reducing runoff (which would have increased 180% if a
standard storm sewer system had been used), and maintaining the water table, which
would have been impacted if storm water were removed through a sewer system (54).

Village Homes in Davis, California, a development built in the mid 1970s, was
one of the first subdivisions to use vegetated swales to allow storm water to be absorbed
rather than sent as a large bolus of water through the storm sewer system to treatment
plants (57). The swales serve as landscape buffers between houses and provide
greenspace in addition to mitigating storm water flow.
Swales are not without disadvantages, which include potential odors from
standing water, and risk of becoming mosquito-breeding areas(56). In Weld County, the
mosquito borne West Nile virus is a continuing health hazard, thus vegetated swales,
while functional, may not be the best choice for storm water mitigation in this area.
Porous pavers in roadways and driveways would also allow storm water to
percolate into the soil rather than run off as a surge, contributing to erosion or creating
pollution problems. These might be a more reasonable choice for managing storm water
in a natural and beneficial manner in Colorado.
Cluster/open space/conservation developments thus also allow alternative
methods for mediating storm water runoff, allowing the precipitation that falls in an area
to re-enter the soil and preserve many aspects of the natural hydrological cycle of a place.
It will be possible to develop methods that work in Colorado without increasing danger of
West Nile virus exposure.
Mid-scale approaches to design:
Improved efficiency of water use depends on mid-scale design decisions as well
as those involving the entire development. Mid-scale design decisions act at the level of
two to five houses, and include clustering the houses, creating gradients for channeling
surface water flow between houses, generating an intermediate greenbelt, and
constructing engineered wetlands for wastewater treatment that would service a housing
Clustering of houses:
As discussed in the previous section, clustering houses on smaller lots increases
local dwelling density, thus improving water efficiency by decreasing the amount of
landscaping and hence landscape watering (Figure 16). Clustering also preserves open
space, which can be used for agriculture, livestock grazing, wildlife habitat, truck farms,
community gardens and orchards, or recreational hiking and biking trails. Keeping the

land open reduces the hard road and parking surfaces, diminishing development costs but
also lessening storm water runoff from the hardscapes.
Slope gradients for surface water flow:
The gradients of streams vary from about 15-25% in very rapidly flowing
mountain streams to about 0.1% in slow moving rivers near the ocean (58, 59). If the
slope of a water course is 1 % or greater, the stream/river will tend to erode the
surrounding soil or rock over which it flows; at slopes less than 1% the water will tend to
deposit whatever it carries(58, 59). In developing human made channels to direct water
across house lots, it is best not to contribute to erosion, but to keep the slope of the new
channel(s) at 1% or less (Figure 17).
Engineered wetlands:
Engineered or constructed wetlands replicate the natural wetlands flora and fauna
as closely as possible as a mechanism to treat and purify water biologically rather than
chemically. Engineered wetlands have been used to treat water heavily contaminated with
petrochemicals, heavy metals, pathogenic organisms and other pollutants (60).
Engineered wetlands have been found to work year round, even in climates with severe
winter conditions, if appropriately designed (60).
Engineered wetlands can contribute to water sensitive design for arid lands in
several ways. First, wetlands constructed to treat septic effluents from several houses
work with smaller surface areas that are equivalent to leach fields, allowing the houses to
be clustered closer, contributing to density associated water savings. Second, wetlands
provide a watery habitat for plant and animal species, providing a desirable water
feature and green respite area. Finally, wetlands can improve return flow of household
water into the local watershed, rather than removing wastewater to a distant treatment

Hypothetical section from stream source to final outflow
Figure 1 7. Stream gradient and land use: slope must be less
than 1 % to prevent erosion (modified from
effluent water level kept below gravel surface
gravel sand
V /
outflow purified water
semipurified water pumped
into unlined gravel-lined wetland
Figure 18. Engineered wetlands: typical paired treatment ponds for
domestic wastewater (modified from Weston et al, 1999).

There are several types of constructed wetlands, but the principal differences are that in
one class the water to be treated flows on the surface into open treatment basins whereas
in the other class effluents are piped below ground into treatment basins that keep the
water lower than the top of the basin. Wetlands for treating sewage or septic tank
effluents usually have a below grade pipe connection to the sources of the wastewater,
and allow the water to flow through at least two separate wetland areas before release to
the environment. The first treatment area commonly has an impermeable liner of clay or
plastic over which gravel is spread(61). Bacteria, algae and water plants are allowed to
colonize the gravel and the effluent is pumped through the gravels several times to allow
the micro and macroorganisms to remove and degrade contaminants (Figure 18). The
partially treated effluent is pumped out of the first basin into an unlined wetland through
layers of gravel and sand, which have also been colonized by bacteria, algae and water
plants such as reeds and cattails (Figure 14). Often the second, unlined wetland has open
water. The water released from the second basin must be continuously monitored prior to
discharge into the environment, but in most working wetlands is free from pathogens, and
contains greatly diminished levels of heavy metals, organic molecules, phosphorus and
nitrogen compounds. Water from the second basin can enter the environment as surface
flow or be slowly released in the subsurface (Figure 18)(61).
Low water use landscaping:
Another strategy to foster water conservation is to use engineered wetlands or
storm water management areas to provide a green vista in the intermediate distance near
clusters of houses. Engineered wetlands, depending on how many houses each serves,
may have enough water flowing through each day to support a reasonable number of
native trees or shrubs. Species would have to be chosen carefully to ensure adequate
return flow into the watershed. Trees, shrubs, reeds and cattails would contribute to a
lush shared landscape, and might minimize or abolish the need for acres of grass and
non-native trees around each house. Plantings requiring watering should be limited to a
very narrow zone near the house, and collected water should be used to nurture them. The
hard surfaces of a patio, for example, could be used to collect precipitation into an
ephemeral water feature. The goal should be to eliminate all exterior watering with
treated domestic water, which could reduce water use by up to 60%.

Small-scale approaches to design (capture, storage, flow):
In the arid west, adaptations at the scale of the house also contribute to water-
responsive design. House orientation to catch storm precipitation efficiently,
incorporation of small naturally fed water features to replace water-hungry landscaping,
roof materials, use of cisterns, grey water systems and water efficient appliances can
contribute significantly to water conservation and even water self-sufficiency.
House orientation based on storm direction:
The plains east of the mountain front in Colorado receive summer and winter
storms from different directions, thus roofs could be oriented with long axes in several
directions to maximize capture of snow and rain (Figure 19).
Roof orientation and slope:
Roofs are excellent water capturing surfaces, covered with hard, water resistant
materials, as their primary function is to keep the insides of buildings dry. The amount of
water that falls on the roof depends on the annual precipitation and the surface area of the
roof: amount water collected (gal)= 623x13in water/yr/1000. The amount actually
collected depends on the efficiency of the harvesting process as well. Table 1 illustrates
the gallons of water as a function of roof surface area and collection efficiency. The roof
on an average sized house (2400 sq. ft house with 45 simple gable and roof surface area
of 3300 sq. ft.) could produce 25, 000 gal water per year at 100% collection efficiency,
18,000 gal/yr at 75% collection efficiency, and 12,000 gal/yr at 50% collection efficiency
(Table 1). The water collected from the roof could be used in lieu of treated domestic,
drinking grade water for non-potable uses such as exterior watering, washing cars,
flushing toilets or washing clothes. If stored and treated, water from the roof could be an
adjunct source of potable water.

Roof modeled 45 gable
Gal water collected based
% replacement landscape use
as function of capture
Fr house Fr roof 100% 75% 50% 100% 75% 50%
6000 8400 62,798 97,099 31,399 142% 107% 71%
3000 4200 31,399 23,549 15,699 71% 54% 36%
2400 3360 25,119 18,839 12,559 57% 43% 28%
Table 1. Water collection capacity depends on roof surface

Roof materiality:
Roofing materials may affect the amount and the quality of water that can be
harvested. Asphalt shingles, a common roofing material, may release organic compounds
and other toxic materials into harvested water (62, 63). Also, as the shingles are porous,
runoff from the roof is not as efficient as would be possible with a less porous surface.
Treated wood shingles or shakes are another common roofing material that could be used
on a roof designed to collect water. Toxic chemicals or metals such as arsenic used to
treat wood could prove problematic, especially if the harvested water is used for drinking
or cooking. Wood shingles, due to surface roughness, may not shed water particularly
Concrete or clay tiles, as they are common roofing materials, could be used on a
water collecting roof, but, as they are more porous than some other materials such as
metal, should be treated or sealed so that they shed water efficiently. Real slate tiles are
water resistant and would make excellent water collecting surfaces.
Metal roofing is water impermeable; rainwater and water from melting snow can
be collected into gutters with little loss except to evaporation. Metal roofing can also act
as a dew collector: metal is an excellent black body radiator, meaning that as it radiates
energy in the form of heat to the night sky, its surface temperature can fall below the air
temperature, allowing the metal to act as a condensation surface for water vapor in the air
(64). Metal roofing is likely the best material for water collecting roofs for several
reasons including smoothness, water impermeability, efficient black body irradiator, and
durability. Metal roofing materials are not without problems, as steel, galvanized steel,
copper and lead may leach heavy metals into the collected water, especially if the water is
Patio surfaces can serve as excellent additional water capture devices, augmenting
rainwater and snowmelt recovered from the roof. Patios, which provide enjoyable
outdoor living spaces, thus can also function as an integral part of the water collection
system of the water-responsive home. It doesnt take much compaction for soil to collect
runoff; the Anasazi stomped the earthen floors of their small storage reservoirs to capture

water (Figure 20) (65). They also used their feet to tamp down large flat areas from
which the water was shed into storage ponds and reservoirs(65).
Figure 20. Anasazi tamped earth and checkdam water capture
And storage system still in use in 1911

Cisterns and smaller rain barrels can be used to store rainwater and snowmelt
collected from roofs or patios, delivering water later to gardens, toilets, washers and
dryers or to taps for drinking and cooking water. Storing water that falls on site as
precipitation can decrease household reliance on city water supplies, especially useful in
decreasing the use of potentially scarce water on landscaping.
Water shed from roofs can be collected into gutters with leaf screens that feed into
the cistern (Figure 21) (63). Many cistern systems have a roof washer, a mechanism for
wasting the first 10-12 gallons collected off the roof in order to remove dirt, foreign
objects like cats, and pollutants that are washed off the roof with the first few gallons of
precipitation, before the bulk of the rainwater enters cistern storage (Figure 21 )(63).
Cistern water can be used directly for watering gardens, but must be purified if used for
household washing or drinking. Cistern water is usually pumped through a series of
filters to remove organic compounds, salts, bacteria and other microorganisms. Many
systems contain an ultraviolet light sterilizer to kill viruses that are so small they pass
through the pores of the smallest filters available (Figure 21 )(62).
Cistern systems can have city water intertie, so that the plumbing has
appropriate valves to shut off the cistern supply when low and switch the household
water supply to city water (Figure 21, right side)(62). It would be advisable to provide
cistern water level monitoring devices in prominent places, like the kitchen, in addition to
a water meter, in the interior of the house so that the residents are aware of how much
cistern water is available. Homeowners could then make decisions about water use.

percent of total domestic
water use replaced by stored
Figure 21. Section of living pavilion with cistern system
to supply domestic water from captured precipitation. Water
is purified for drinking; valves allow cistern and city water to be
used interchangeably as needed.
Storing water in cisterns decreases burden on municipal water supplies
35% -|
30% -
25% -
20% -
15% -
10% -
5% -
0% -
90% capture
75% capture
percent domestic water used for
landscape watering
Figure 22. Captured precipitation can replace up to 1/3 of
Domestic water demand depending on exterior water use
(landscape watering).

Cisterns that store rainwater and snow work well for providing water for domestic use;
the amount of water available for storage depends on the annual precipitation in any area.
Work in Texas suggests that 24 inches/year of precipitation is the minimum required to
provide all of a typical familys annual water needs. As the average precipitation in the
plains east of the mountain front in Colorado is much less than this, storing precipitation
in cisterns will never replace all of the water needed for domestic use. The water
collected from the roof over a 2400 sq. ft. house at 75% efficiency (a conservative
collection efficiency) could only replace about 10% of the annual per household water
consumption (Figure 22). If all landscape watering were eliminated, captured water could
replace about 25% of the annual water required. If the collection efficiency improved to
about 90%, and landscape watering were eliminated, water captured from the roof could
replace over 30% of the yearly water used by the average household (Figure 22).
Replacing 25% to 30% of domestic water with site-derived water, multiplied by the tens,
hundreds or thousands of homes in a development, would significantly decrease the
burden on municipal water providers.
Cistern use is not without problems, however. Colorado water law requires that
cistern users go to water court to obtain an allocation decree before using cisterns to store
rainwater or snowmelt, although in practice the law is seldom enforced. If large numbers
of homes were to install cisterns or rainbarrels, the legality of these would doubtless be
challenged, and mechanisms for augmenting (replacing) water into the watershed would
have to be developed. It is possible that treated wastewater flow out of engineered
wetlands into the local natural hydrologic cycle would be more than sufficient to replace
water stored in cisterns, but this would need to be explored in more detail.
Ephemeral water feature in patio:
The hard surfaces of patios, wonderful adjunct water capturing surfaces, can be
graded so that the collected water drains into a central water feature, rather than
draining into a cistern or other hidden water storage facility. The surface water feature,
which would be ephemeral, could be used to water small planting beds, providing an
oasis in the middle of, or on the edge of, the patio area. A small area of greenery would
allow for near distance or middle distance visual relief, depending on where the water

feature was located. The ephemeral nature of the water feature would also remind the
occupants that water is scarce in the west.
Snow corrals:
Snow contains variable amounts of water, ranging from about 1 % to 25% by
volume. Snow water content depends on the time of year in Colorado, the most water-
rich snow arriving in March, April and early May(66). As March, April and May also are
the months with the highest amounts of precipitation in the high plains just east of the
mountain front (Figure 23), it would be sensible to store snow, especially spring snow, as
a water source. Snow storage areas, or corrals, could be designed on the north sides of
residential units. Snow corrals would need to be protected from direct sun and from
strong winter winds, and would require some mechanism for delivering water from
melted snow to exterior plantings or to storage systems.
Figure 23. Total water content of precipitation in Weld
County. Wet snow in March and April contribute a
substantial portion of annual water.

Water efficient plumbing fixtures'.
Water efficient plumbing fixtures, although not directly affecting water storage,
do affect water use. Washing/bathroom water use is second only to landscape watering in
percent of domestic water consumption. As many Western states have faced serious
drought induced water shortages in the last few decades, the incentive for developing low
water use washers, showerheads, toilets, dishwashers and other water requiring
appliances has increased. Any residence built in the arid high plains east of the mountain
front should include the full complement of low water use appliances that are available
and/or appropriate. Low water plumbing fixtures are standard and are made by many
Engineered wetlands:
As discussed in the section on mid-scale strategies for water conservation,
engineered wetlands, shared between several houses in a cluster, can be used instead of
septic systems. Engineered wetlands allow houses to be clustered more closely, can be
used for storm water treatment, and enhance return of treated water into the natural
hydrologic flow of a site. In addition, engineered wetlands provide or replace habitat for
animals and plants. Artificial wetlands supply water for lush plant growth in their
immediate vicinity, giving contributing homes a green landscape element. If wastewater
outflow is sufficient, engineered wetlands can even support growth of large trees.
Advanced greywater treatment
Figure 24. Greywater: reusing washwater from showers, sinks, laundry for
landscape watering. Greywater should be treated before reuse.

Greywater systems:
Greywater is all wastewater from domestic water use except water from
toilets(67). Greywater can be recycled for exterior irrigation, and non-contact interior use
such as toilet flushing and first cycle clothes washing (67-70). Greywater may be pumped
without treatment onto exterior plantings, but it is advisable to treat wastewater prior to
recycling. There are many techniques for treating greywater, including coagulation,
filtration, settling tanks (sedimentation), and disinfection (Figure 24)(47, 67, 71). Reuse
of greywater, especially for exterior watering, which may account for up to 60% of
domestic water use in Colorado, and for toilet flushing, which may use 30% of interior
water, would contribute considerably to water conservation(47, 67).
Denver Water has completed a greywater treatment plant, which will serve
schools, some industries such as powerplants, parks and golf courses so that treated
drinking water will not be wasted on landscape watering(47). Widespread utilization of
greywater for outdoor needs could decrease residential water use significantly by
replacing treated drinking quality water with recycled water.
There are many valuable strategies and mechanisms for improving efficient use of
household water, as described in the preceding section. In applying these strategies to the
design of a single residence, or cluster of residences, choices must be made based on the
specific characteristics of the site, as described in the next Chapter.
The patterns or strategies for water-responsive design are meant to provide some
choices in developing a site appropriate building that uses water as efficiently as possible.
The prototype house discussed below illustrates several design strategies that, together,
may result in a building that uses natural precipitation as a water source and disposes of
wastewater in a way that augments slow water release from the site.
Site and site issues:
The site for the prototype house is on a 300-acre parcel of farmland between
Milliken and Evans, southwest of Greeley, in unincorporated Weld County (Figures 25
and 26). The 300 acres of farmland are near the edge of the low bluffs that edge the north

bank of the Big Thompson River near its confluence with the South Platte River. The site
is relatively flat, with an average gradient of 3-4%. The south and southwest portion is
steeper, sloping down towards the river at a gradient of 10-20% (Figure 27).
Figure 25. The site for the case study is southwest of Greeley
In unincorporated Weld County, between Evans and Milliken.
Figure 26. The site is above the confluence
of the Big Thompson and South Platte Rivers

Figure 27. The case study site is a 300 acre parcel of
dryland agricultural land above the Greeley-Loveland Canal.

The land is in a part of Weld County with irrigated farmland of national importance in the
river bottoms and along the irrigation ditches, meaning that the land is quite fertile when
water is applied (green in Figure 27). The 300-acre site is above the Greeley-Loveland
Canal, which runs along the bluff tops to the southeast, and therefore is now in dryland
crops, but is classified as prime land of national importance if it could be irrigated
(yellow in Figure 27) (66). If farmland must be turned into suburban developments, it
would be prudent to reserve the best, most fertile, easiest to irrigate fields for agricultural
use as long as possible and to put housing in dryland crop areas. From this perspective, it
is better to develop the 300-acre parcel than the irrigated land immediately to the
southeast, although the latter is closer to Greeley and Evans, and borders land that has
already been subdivided.
The average annual precipitation in western Weld County in the Greeley area is
12-13 inches of precipitation per year (Figure 28). For developing water responsive
residential design the average precipitation is assumed to be 12 inches per year. The site
receives more precipitation during the period March-June than other times of the year. In
March and April, the area receives water as snow, whereas later in the spring
thunderstorm activity delivers water as rain. Snow has variable water content, ranging
from about 1% in November and December to about 25% in April and May; the average
is about 10% (66). Thus, in an average year, the site would receive the most water as
snow in March and April, with lesser amounts of water delivered as rain during the spring
and summer thunderstorm season (Figure 23). The prevailing thunderstorm direction is
from the west-southwest, and the wettest snowstorms come from the northwest-north, so
architectural strategies to intercept precipitation, such as roofs placed with long axes
perpendicular to the average storm direction or snow collection areas to trap blowing
snow, should take common storm directions into consideration.

Water: Annual Precipitation
Figure 28. The area of the case study receives 11-12 inches of
precipitation per year.
SUMMER 12.5 mph
WINTER 14.5 mph
Figure 29. Wind direction varies as a function
of season. Strong winter winds from the north
switch to easterlies in the summer.

The dominant wind direction in the winter is out of the north and in the summer is out of
the east (Figure 29). As wind can evaporate accumulated rain and cause snow to
sublimate, open water features or snow storage areas should be protected from winds. A
wall or a windbreak should be placed on the north side of snow storage areas, and
summertime rain storage should be protected on the east side. Figure 30 summarizes the
site conditions and considerations that contributed to the final design of a prototype
The average density of housing in unincorporated Weld County varies from
several houses per acre to one house per five to seven acres. For the purposes of this
project, it will be assumed that the development will be for houses of higher value, at the
upper end of the housing market, and therefore, low density: one house per five acres. In
this case, sixty houses would eventually be built on the 300-acre site. A 25-acre parcel
near the center of the 300 acre site was chosen as the site for the prototypical housing
cluster (Figure 31) in which the prototype house is located. The standard method for
platting subdivisions would be to place each house close to the middle of a roughly
rectangular five-acre plot, which would result in houses dispersed more or less evenly
across the entire site without regard to natural variations in topography, which dictate the
ways that water would flow across the site in the absence of human, or grade-all,
interference. If the object is to create a built environment that is sensitive to water
scarcity, it would be better to place houses to take advantage of natural flow patterns
across the 300 acres (Figure 32A, B and C), so that runoff could be used to create green
spaces around the houses, or so that existing watercourses could be used to channel
wastewater from engineered wetlands through the site. In addition, clustering houses
more densely than one house per acre would allow much of the 300-acre site to remain
open, as either jointly held private open space, grazing land for horses or other livestock,
or as agricultural land.

Figure 30. Summary of site considerations for design.

Figure 31 .Prototype housing cluster on 25 acre site
within 300 acre parcel
Figure 32. Cluster houses in
25 acre subparcel along natural
water runoff channels
V. -3


Figure 33. Houses cluster around engineered wetlands. Landscaping
is minimal, and engineered wetlands, patio water features provide
green relief.
Figure 34. The prototype house
integrates capture, storage, outflow. cistern
^ cistern

The prototype house therefore is in a hypothetical development with houses clustered at
densities of 2-3 per acre around engineered wetlands that function as wastewater
treatment areas, wildlife habitat, and green oases in the dry upland grassland that was the
native condition of the site (Figure 33). Engineered wetlands also are a mechanism for
replacement return flow for water temporarily stored on site in cisterns, small water
features, or ponds.
Prototype house:
The prototype house, approximately 2300 square feet, is close to the average size
of a single-family house, which was about 2200 square feet in 1999 (72). The size of the
house was determined by the attendant roof surface area, which serves as a rain and snow
collection system, in addition to the usual function of roofs in keeping wet outside. As
described in detail in Chapter 3, the roof surface area covering a 2400 sq. ft. house would
be about 3300 sq. ft. if the roof were gabled with a 45 slope. If 75% of precipitation, rain
and snow, falling on the roof were collected, accounting for losses due to sublimation,
evaporation and leaks in the collection system, about 18,900 gallons per year could be
gleaned (Table 1). As the typical single-family household uses about half an acre-foot of
water per year for all purposes, including landscape watering, harvesting water from the
roof could replace approximately 11 % of domestic water. However, if landscaping
watering in the water responsive development could be abolished by a combination of
strategies including use of plant species that are drought tolerant, limiting plantings to a
narrow zone near the house, using the hard surfaces of a patio to collect precipitation into
an ephemeral water feature, and allowing the engineered wetlands to provide the water
for any trees or larger shrubs in the housing cluster, the annual domestic water use could
be reduced by as much as 60%, falling to 65,000 gal/yr, or 1/5 acre-foot/yr. If this were
accomplished, the amount of water provided by roof collection systems could increase to
30% of the total water use per household. As long as return flows for downstream users
could be guaranteed, roof storage systems could significantly decrease the burden on
municipal water supplies.
Although the primary focus of the proposed house design is water efficiency, the
goal is to develop a sustainable yet comfortable single-family residence adapted to the
arid conditions of the high plains east of the mountain front. Therefore, strategies to

improve overall self-sufficiency and sustainability, including incorporating building
systems and materials made from renewable resources, orienting the house to maximize
solar gain for heating, and cross ventilation for cooling, and integrating natural
daylighting by thoughtful window placement are also essential parts of the design.
The house is a series of three connected pavilions oriented along a major east-
west axis (Figure 34). The pavilions each have southern exposure for winter solar heat
gain, small east and west facing windows to minimize spring and summer overheating,
and north windows for daylighting when possible. Breaking the mass of the house into
three volumes minimizes the potential bowling alley feel of a long, narrow house while
maintaining an equivalent amount of southern exposure. Allowing the three volumes to
shift along a north-south axis also creates shady areas for the patios on the south side,
making this space habitable and pleasant in the summer, especially in the evening when
low angle sun from the west-northwest can cause outdoor spaces on the south and west
sides of homes to be very uncomfortable.
The prototype house will capture water in three places: roofs, patios and snow
storage corral. Each of these capture areas is oriented in a slightly different direction to
take advantage of water in precipitation at different times of the year.
As described above, most water in this part of Colorado arrives in the form of
high water content snow in March, April and May, which is the wettest month in the
plains near the mountain front (73). The wettest winter storms in the plains just east of
the Front Range come from the north-northwest, as do the strong winter winds (73).
Therefore, a snow storage area or corral on the north side of the house, with a protective
wall to the north, is an essential part of the water collection system. The corral would
have a drain, with protective screening, that would deliver water from melting snow into
the cistern storage system (Figure 35).

t-. .
-1 J
!c=. 'SLi
m u ;t:
Snow corral on north side stores
winter snow and shunts snowmelt
North Elevation into cistern for storage
Snow corral ,
Ik A
Figure 35. A corral stores snow on the
north side of the house, delivering the
snowmelt to the cistern for storage.
West Elevation
Figure 36. Cisterns
buried on the west
and east sides of the .,,1
. -r~'
house store water \ i ^
V** "
collected from
pitched roofs through
a gutter system.
East elevation

Pitched roofs with gutters shunt runoff to cisterns

T r*
Patio with hard surface for water collection
South Elevation
Figure 37. A paved patio also serves to
capture precipitation, which is stored in
an ephemeral water feature, reminding
the inhabitants of the fleeting availability of
water in this climate.
V" '
effluent water level kept below gravel surface
gravel sand
V /
outflow purified water
semipurified water pumped /
into unlined gravel-lined wetland /
(modified from Weston et al, 1999).
Figure 38. A. Section of proposed engineered wetlands illustrating
wastewater flow from prototype house through septic tanks into ponds.
B. Wastewater is treated first in lined pond, then, when purified, is
pumped into unlined pond for further bioremediation. Water released
to environment from second pond.

The house has pitched roofs, to increase roof surface area and capture efficiency, as the
amount of water available for collection/storage is a function of surface area and annual
precipitation (Figure 36). Summer thunderstorms tend to come from the south/southwest,
so the house is oriented with the long axes of the pavilions perpendicular to the prevailing
thunderstorm direction (axes east-west or southwest-northeast). The roofs will have
gutters channeling rain and melted snow to below grade storage.
The roofs will be standing seam metal rather than asphalt shingle or other roofing
materials. Although galvanized steel roofs do release some zinc and other heavy metals
into captured rain and snowmelt, the amounts of metal released in precipitation of neutral
or slightly acidic pH value is less than the potential release of hydrocarbons and organic
compounds from asphalt shingles. Concrete tile is more inert than either sheet metal or
asphalt shingle, and would therefore make an acceptable trapping surface. One advantage
of metal roofing is that, if the roof is properly insulated, it acts as a blackbody radiator at
night, and can cause condensation of atmospheric water as dew on its surface as a result.
Dew can also be collected in the gutter system and channeled to storage.
A paved patio on the south side of the house will also be used to capture snow and
rain. The patio will be graded so that there is a central depression that will act as an
ephemeral water feature (Figure 37). Drought tolerant plantings around the depression
will provide a green respite space or oasis close to the house that will be visible from the
three pavilions. The residents will be aware of the presence or absence of water in the
central depression, and will have a stronger sense of the regional aridity as a result
(Figure 37).
Captured water from the roofs will be stored in three below grade cisterns, one for
each pavilion. The gutter system from each roof will channel water through a roof
washer, a small volume spillover system to remove the dirt and debris washed off the
roof in the first minutes of a rainstorm, prior to delivering the bulk of the collected water
to the cisterns. The cisterns will have access portals at grade for cleaning and
When needed, water from the cisterns will be pumped through a series of
purification filters in the basement of the central pavilion. The water will pass through an

activated charcoal filter to remove organic compounds and dissolved ions, and a series of
small pore filters (5p and 2p) to remove bacteria and other microorganisms. The final
treatment will be a UV sterilizer to kill any viruses that might remain in the water. The
cistern will have level detectors, and the residents will be able to use cistern water when
available, but switch to city water if necessary (Figure 21). One way to make residents
more aware of water use will be to install a water meter showing cumulative use in a
prominent place, such as the kitchen, in addition to displaying water levels in the cisterns.
Some of the water from precipitation that falls on the site will be stored in an
ephemeral small pond or water feature in the outdoor patio on the south side of the house.
As described above, the pond will provide some moisture to surrounding plantings and
will serve as a visual oasis for the house. The residents will be able to see when the pond
has water and when it does not, and may take cues for water use from what they see
(Figure 37).
Water would leave the site in several ways: as wastewater from inside and as
uncaptured storm water outside. Several strategies for treating and/or recycling water
were presented in Chapter 2, including ideas for allowing storm water to be adsorbed on
the site, recycling domestic wastewater, and on-site treatment of wastewater in
engineered wetlands. In order to replace water stored in cisterns, a system that
combines storm and wastewater treatment and outflow through engineered wetlands into
the watershed is proposed. Waste and storm water from several houses (3 to 5) would
flow into shared wetlands, ensuring that the system would have sufficient water flow to
function properly. Recycled greywater could also replace city water or well water
(groundwater) for landscaping. One advantage of wetlands is that the water released into
the environment is cleaner than recycled domestic wastewater usually is when used for
irrigation. Wetlands effluent is usually neutral to slightly acidic in pH, whereas greywater
is usually quite alkaline due to soap (67). However, shared wetlands for wastewater
disposal would remove the possibility that greywater could be used to irrigate landscapes
around individual houses. Housing clusters in the wetlands scheme would share natural
green space around the wetlands, but have limited landscaping around individual units.
The ephemeral water features in patios could be used to water small amounts of plants

close to each house, but extensive green zones would not be encouraged. Therefore,
storm water from the patios would be collected into a central water feature by grading the
patios appropriately, and storm runoff from other parts of the site would be diverted into
the wetlands for treatment prior to release into the environment.
Most precipitation falling on the roofs of the prototype houses would be collected
and treated for domestic use, and exit the house as wastewater. The wastewater from the
houses would empty into standard septic tanks, but the effluent, rather than flowing into a
leach field, would be piped into engineered or constructed wetlands downstream from the
house and its close neighbors. The septic tanks for each house in the cluster should be
located on the opposite side of the house from the cisterns to prevent accidental
contamination of the household water supply. Use of engineered wetlands to treat the
household wastewater contributes in many ways to a sustainable approach to residential
development. First, as noted above, the legal use of a cistern requires supplying timely
replacement flow to ensure that the water rights for downstream users are not affected (no
injury to senior rights holders), and biological treatment of household wastewater should
return more than the volume of water stored in cisterns. Second, use of engineered
wetlands will allow houses to be built closer together as the need for extensive septic
leach fields is obviated, thus preserving more open land. Third, engineered wetlands
remove more water pollutants such as phosphorous and nitrogen compounds than
standard leach fields, as the microorganisms and plants in the wetlands use these to
support growth. Wetland organisms, as described above, also remove heavy metals from
the wastewater, and can degrade a number of organic molecule contaminants as well,
resulting in the release of fairly clean water into the watershed. Finally, wetlands can
provide an attractive feature in the middle landscape as they support trees and larger
shrubs, reeds, cattails and serve as habitat for waterfowl, mammals, smaller birds, fish
and amphibians. Probably snakes too.
The septic tank effluent would be piped underground into a sealed or lined
wetland for the first stage of remediation (Figure 38). Most systems contain a recycle
loop, so that the effluent passes several times through this area. Treated water from the
lined wetland would be piped under the surface to the second, sand and gravel lined
wetland system. Microorganisms colonizing the sand and gravel continue the remediation

process and the water leaving this part of the engineered wetlands should be suitably
clean, but will be monitored professionally. The size of wetlands required to handle
typical household wastewater is not excessive: as shown in Figure 39, wetlands with radii
as small as 30 feet would be sufficient to hold the volume of wastewater from the typical
single family home. As water would flow through the system continuously, the actual
size needed would likely be far smaller. The constructed wetlands would have to be
designed and maintained by an engineer specializing in these alternatives to the standard
septic system, but there are several firms in the Front Range that have the necessary
The prototype house therefore would be able to capture, store and dispose of
water arriving on site as precipitation. The strategies for water management described
above might be able to replace as much as 30% of the water used in a single family home
each year. If this proved possible, such houses would create a significant reduction in
water demand, and might contribute a partial solution to the water supply problems that
will become critical in the not too distant future.
Other issues in sustainability: structure, materiality and orientation of the prototype
Water efficiency and self-sufficiency are both important aspects of sustainable
design on the scale of the individual building, the level of building clusters and entire
developments, towns and cities. Water efficiency, however, is only part of, although an
important part of, a sustainable approach to building. There are numerous other design
choices that contribute to the environmental impact of any building: choices about
building structure and materials, building orientation for light and heat gain, building size
and profile. These are beyond the scope of this work to address in detail, but each was
considered and decisions were made during the course of design.

(/) 140000 n
| 120000 -
c 100000 -
S 80000 -
{§ 60000 -
m 40000 -
£ 20000 -
Depth of wetlands
radius of wetlands
Figure 39. Wetlands do not have to be large to handle the
volume of wastewater generated in a typical household
Figure 40. The structure of
the house is comprised of load
bearing box columns with straw bale
infill. Wood for the structural framework
would come from deadfall or sustainably
harvested forests. The straw could be
grown on site. Windows would be
placed to maximize daylight penetration
and minimize summer solar heat gain or
winter heat loss.

The prototype house structurally is load-bearing wood frame with straw bale infill
(Figure 40). Wood framing systems, when analyzed for overall environmental impact
throughout the life cycle of the building, are quite sustainable. The environmental impact
of wood framing versus light gauge steel framing was compared using the life-cycle
analysis program BEES (Department of Energy): wood harvesting and conversion to
lumber produced a 10-fold lower effect on global warming (C02 emissions) than steel
framing, and wood framing received a 10-fold higher score in other aspects of
environmental performance including fossil fuel depletion, habitat alteration, generation
of other air pollutants, and water use during manufacture than steel framing. There is an
increasing focus on sustainable forest management in Colorado, and there are wood
products available from live trees harvested in a sustainable manner, and from harvested
deadfall. The wood framing system would be made from such wood products.
The straw for the straw bales could be grown on the site, minimizing transport
costs. Clay for the adobe-concrete exterior and interior wall finish could also be obtained
locally, as clay rich layers exist in the Fox Hills sandstone, of which the nearby river
bluffs are composed.
The prototype house is oriented with the long axes of two of the three pavilions
running east-west, which maximizes south and southwest exposure for winter solar heat
gain. The overhanging eaves would protect the interior from excessive heating during the
spring, summer and fall, but let low-angle winter sun deep into the interior. The flooring
in the prototype house would be tile, a relatively absorptive, high heat capacity material
that would release heat slowly through the night.
The pavilions of the prototype house are longer than wide, with abundant high
north facing windows, to allow deep penetration of daylight into the interior. Windows
on all sides also provide cross ventilation, minimizing or abolishing the need for central
air conditioning in the summer.
Although landscaping should be kept to a minimum, especially plantings of water
devouring non-native grasses and trees, most of us want to see some green and lush
vegetation immediately around our houses or in the middle distance. The patio water
feature, and the mid-distance engineered wetlands, can provide some very green spaces
of very limited extent for the prototype house. In addition, drought tolerant, native

species can be chosen for landscape elements. Some of the native bunch grasses are green
in the spring and early summer, turning dormant only in the heat of the high summer.
The prototype house is meant to have as small an impact as possible on the site in
Weld County (Figure 41). The proposals for increased water efficiency/self-sufficiency
are palliative, and would, if widely implemented, slow but not stop the inevitable water
crisis. Growth is not infinitely sustainable, despite the catchphrase so commonly used.
We have some very difficult choices to make in the next quarter century about our use of
increasingly strained resources.
Figure 41. An approach to water self-sufficiency
and sustainable living in this landscape.

As the state of Colorado copes with a population double that of 2000 by 2030,
Coloradoans will have to make difficult choices about land use patterns, about
distribution of increasingly scarce resources such as water, and about placement and
types of necessary infrastructure like roads, rapid transit systems, water treatment plants,
and power plants. Residents, would-be Coloradoans, and tourists are all drawn to the
wild-west image of Colorado: the Colorado of Denver City, of gold miners, of
Cowboys and Indians, of pioneers, homesteaders and ranchers. Our problems come from
the fact that our very attraction and attention to places in Colorado tend to change these
places forever.
We search for an antidote to the inevitable changes that anyone living in Colorado
for even a very few years has witnessed. We use words like smart growth, or
sustainable development, in the hopes that the words themselves will slow down what
we hate to see: a multilane highway plunging deep into quiet grasslands where once we
walked, condominiums marching up the slopes of what was a remote mountain valley
until the roads, until the ski area, anonymous subdivisions sprouting like mushrooms
seemingly overnight in fields that last season grew corn, or spring wheat. We hate to see
these things, but we drive on the highway, we buy the condos and the bigger and better
homes. We forget, quickly, what used to be in the convenience of what is. We want the
economy to grow so that we are increasingly prosperous. Enough is never satisfying.
Whatever we like, however we feel, this is an arid landscape, prone to extremes of
climate, heat, cold and especially drought cycles; we have no control over the
geologic/geographic/climatic realities of Colorado (74).
One of the most fundamental problems is that there are too many of us who want
to live in Colorado. If we want to preserve a tolerable future environment, one in which
there are not 18 million people in the state by 2050, as would be the case if the population
continued to increase at the present rate, we have choices to make: one is that we can
choose to stop people moving into the state. The impracticalities of this solution are
multiple, the economic consequences are likely to be unpalatable, and the population
would continue to increase anyway as the birth rate exceeds the death rate. We can take

the more difficult route of planning for the expected growth, deciding as communities
and regions when and where land is developed or infrastructure is built. We can
strategize how to direct, or modulate or slow growth to a rate that will not destroy what
we have and that will not strain our available resources beyond their limits. This would
be difficult, contentious, and unpopular with many of the entities that would perceive loss
by changing the status quo. Regional or even statewide planning would be a labor and
time intensive exercise, but the recent success of the State Water Supply Initiative
(SWSI) in convincing all the parties concerned with water use, the ranchers/farmers,
municipal water boards, private citizens, and private water developers, to participate in a
productive dialog suggests that other regional and statewide long term planning strategies
might similarly result in dialog if not immediately in consensus.
The question of what is meant by sustainability remains. Those of a radical anti-
growth position would maintain that growth is inherently not sustainable. No living thing
grows infinitely; all organisms eventually reach the end of the food, or the space, or the
carbon/oxygen; something in the environment always becomes limiting. We are not yet
smart enough to escape this reality. Sustainability to some means increasingly or
exclusively using renewable resources, or those that are replenished within human scale
time, rather than nonrenewable resources, or those that are replenished in geologic time,
for buildings, for fuel, for clothing and all the other consumables that we require. To
others, sustainability is merely a term that can be used to market specific upscale goods to
the affluent.
It will be difficult to address growth related issues on a regional or state level, and
even more challenging to reach a common or consensus strategy or set of strategies for
managing growth in a manner palatable to many if not all Coloradoans. In the interim,
designers of the built world can offer some alternatives, partial or incomplete as they may
be, to the usual development practices. There are variants on the standard subdivision that
improve the sense of community, or preserve open space and habitats, or decrease vehicle
use by providing the daily necessities within easy walking distance, or improve the lives
of children or the elderly by fostering independence from the car and an accessible
community(75, 76). None of the alternative suburban models work perfectly or are

universally accepted, but each allows homebuyers a choice, and each provides the
opportunity for testing new ideas and for further improvement.
There exist multiple strategies for slowing growth, including strictly allotting and
limiting building permits on a statewide level like New Hampshire, or requiring
developers to pay more of the true cost of development, which makes houses far more
expensive, and encourages limits on size, higher density developments and fewer internal
roads (77). The alternatives allow for the exercise of private rights in preserving the
ability of landowners to profit from their land, either as farmers/ranchers or as
developers, while discouraging resource intensive development.
This work has concentrated on establishing options for residential units that use
water more efficiently than current suburban homes. The finite nature of water resources
in Colorado is but one of many serious issues facing the state as it continues to be one of
the fastest growing in the country. Air quality, availability of suitable land for
development, easy access to transportation infrastructure, may also eventually limit when
and where houses, schools, commercial and industrial buildings are built, but the amount
of water accessible at reasonable cost to municipalities is most likely to become limited
first. Because water is the first essential resource impacted by population growth in
Colorado, the lack of adequate water supplies has already begun to curtail new building
in some areas (31). Any strategies for increasing water conservation will delay, but not
abolish, the inevitable increase in costs associated with diminished supply. The tactics
described in preceding sections aim to move domestic water use towards sustainability.
A sustainable approach to water use would mean that the demand for water would not
exceed the supply, and that the population of Colorado would never increase to the point
that the surface water and groundwater available for consumption, both of which are
finite in amount, were less than municipal water boards were required to deliver to
The proposals offered in this work will not provide solutions to the all the
problems associated with continued high growth rates, but, coupled with other strategies
for slowing growth, might lead to sustainable use of the resources available in Colorado.

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