[PDF]Rainwater Harvesting-Supply from the Sky

RAINWATER HARVESTING



LETTER FROM THE MA YOR



LETTER FROM THE MA YOR



Dear Neighbor,



On behalf of the City of Albuquerque, I am pleased and excited to pre-
sent Rainwater Harvesting: Supply from the Sky . This guide was developed
by the City's Water Conservation Office to assist city residents and businesses
in the campaign to save water.

Achieving our community's ambitious water conservation goals will not
come easily. Doing so will require that we as a community adopt a "water
ethic," and that all of us make conservation part of our daily lives. I believe
this guide can help in that regard because rainwater harvesting, by its very
nature, reconnects people to the environment they live in. It teaches natural
limits while showing that human ingenuity can stretch those limits through
improvements in efficiency and overall water management. Indeed, rainwater
harvesting is the perfect combination of supply-side and demand-side man-
agement techniques, increasing the supply of water while simultaneously
promoting demand-side reductions. Perhaps most importantly, rainwater
harvesting fosters an awareness of one's personal water use and of the
amount of water available from rainfall alone. And, it's something anyone
can do.



"Achieving the higher savings
will require that the City
effectively reach out and
engage large segments of the
public in a shared mission to
save water. In that regard,
Albuquerque will need to
establish a water ethic that
ripples throughout the entire
community, one that can fuel
the program to go above and
beyond what has been done
elsewhere."

From:

Water Conservation Rates and Strategy
Analysis, March 1995



So read this guide, share it with your friends and neighbors, and let us
know what you think about it. But above all, use it to take advantage of the
"supply from the sky." If each of us does just a little to acton the advice
contained within these pages, we will have taken a big step toward ensuring
an adequate water supply for our community today and in the future.



Sincerely,



Jim Baca, Mayor
City of Albuquerque




RAINWATER HARVESTING



ACKNOWLEDGEMENTS



ACKNOWLEDGEMENTS



CITY OF ALBUQUERQUE

Jim Baca, Mayor

PUBLIC WORKS DEPARTMENT

Larry Blair, Director

WATER RESOURCES DIVISION

John Stomp, Manager

Jean Witherspoon, Water Conservation

Officer

ALBUQUERQUE CITY COUNCIL

President

Michael Brasher, District 9

Vice President

Alan Armijo, District 1

Alan B. Armijo, District 1
Brad Winter, District 4
Tim Kline, District 5
HessYntema, District 6
MikeMcEntee, District 7
Greg Payne, District 8
Michael Brasher, District 9



In large part this publication duplicates a rainwater harvesting guide
published by the Arizona Department of Water Resources (ADWR) in
September, 1998. Titled Harvesting Rainwater for Landscape Use, it was
prepared by Patricia H. Waterfall, Extension Agent with the Pima County
Cooperative Extension Low 4 Program, with editorial assistance from Joe
Gel I, Editor, Water Resources Research Center, University of Arizona; Dale
Devitt, Professor, Soil and Water, University of Nevada/Reno; and Christina
Bickelmann, Water Conservation Specialist, Arizona Department of Water
Resources, Tucson Active Management Area. Silvia Rayces prepared the art-
work. We are grateful to ADWR for allowing us to borrow freely from their
publication.

This guide was revised to incorporate New Mexico-specific data and
reformatted to accommodate the needs of the City of Albuquerque. Draft
production was handled by Kevin Bean, of K.M. Bean Environmental
Consulting; Doug Bennett, Albuquerque's Irrigation Conservation Manager;
and Eva Khoury, an Intern with the Water Resources Division of the
Albuquerque Public Works Department. Technical assistance was provided
by Andrew Selby of the Mayor's Office, and by Kay Lang of the Albuquerque
Environmental Health Department. Cooney, Watson & Associates handled
final production. Final design was provided by Ken Wilson Design.



TO ORDER:

Albuquerque residents may order this document from the City's Water
Conservation Office, P.O. Box 1293, Albuquerque, NM 87103.
505-768-3655 (phone), 505-768-3629 (fax), 768-2477 (TTY) or Relay NM
1-800-659-8331. (www address: http://www.cabq.gov/resources.)



If you live outside of Albuquerque, please contact the Office of the State
Engineer, Water Use and Conservation Bureau, P.O. Box 25102, Santa Fe,
N.M . 87504-5102. Orders may also be placed by phone at 1-800-WATERNM .



RAINWATER HARVESTING



TABLE OF CONTENTS



TABLE OF CONTENTS




Letter from the Mayor
Acknowledgements
Table of Contents

Introduction 1

Rainwater Harvesting System Components 2

Simple Rainwater Harvesting Systems 3

Simple Rainwater Harvesting System Design and Construction 4

Complex Rainwater Harvesting Systems 6

Elements of a Complex Rainwater Harvesting System 7

Complex Rainwater Harvesting System Design and Construction 10

Maintenance Checklist 17

Appendix I: Inches of Average Monthly Rainfall for NM Towns 18

Appendix II: Runoff Coefficients 19

Appendix III: Average Evapotranspiration for Selected Areas in NM 19

Appendix IV: Plant Water Use Coefficients 20

Appendix V: Supply and Demand Worksheets 21

Appendix VI: Guidelines for Rain Gutters and Downspouts 23

Appendix VII: How to Build a Rainbarrel 24

Appendix VIII: Whereto Go for More Information 25

Notes 26



RAINWATER HARVESTING



INTRODUCTION



INTRODUCTION




Series of water harvesting basins on a
slope.




Parking lot draining into concave lawn
area.



IMPORTANT NOTES

1. This Guide applies to land-
scape uses of harvested water
only. The use of rainwater for
drinking is beyond the scope of
this publication.

2. Before you start, check with
your local building, zoning and
environment departments to
determine what plumbing
requirements, height and local
restrictions, neighborhood
covenants, or other regulations
or guidelines might apply to
your project.



In the arid Southwest rainfall is scarce and frequently erratic. These
conditions require that water be used as efficiently as possible, and that
we take full advantage of what little rain we do receive to help meet our
water needs.

Rainwater harvesting is the capture, diversion, and storage of rainwater for
landscape irrigation and other uses. Although rainwater can serve as a
source of potable water, this guide focuses on landscape uses because they:
1) account for a significant percentage of total water demand; 2) are less
essential and therefore more easily reduced than water used for other pur-
poses; and 3) need not meet stringent drinking water standards. In many
communities landscaping accounts for 30 to 50 percent of total water use.
In Albuquerque, about 15 billion gallons of water a year are used for land-
scape irrigation.

Rainwater harvesting can reduce the use of drinking water for landscape irri-
gation. Coupled with the use of native and desert-adapted plants, rainwater
harvesting is an effective water conservation tool because it provides
"free" water that is not from the municipal supply. Water harvesting
not only reduces dependence on groundwater and the amount of money
spent on water, but it can reduce off-site flooding and erosion as well. If
large amounts of water are held in highly permeable areas ( areas where
water penetrates the soil quickly and easily), some water may percolate to
the water table.

Rainwater is the best source of water for plants because it is free of salts and
other minerals that can be harmful to root growth. When collected, rain-
water percolates into the soil, forcing salts down and away from the root
zone. This allows for greater root growth, which increases the drought toler-
ance of plants.

Rainwater harvesting can be incorporated into large-scale landscapes, such
as parks, schools, commercial sites, parking lots, and apartment complexes,
as well as small-scale residential landscapes. The limitations of water
harvesting systems are few and are easily met by good planning and design.
There are many water harvesting opportunities on developed sites, and even
small yards can benefit from water harvesting. And, water harvesting can
easily be planned into a new landscape during the design phase. So whether
your landscape is large or small, the principles outlined in this manual apply.



RAINWATER HARVESTING



RAINWATER HARVESTING SYSTEM COMPONENTS



RAINWATER HARVESTING
SYSTEM COMPONENTS




Simple system— roof catchment, chan-
nel, and planted landscape holding area.




Simple system— roof catchment, gutters,
and bermed landscape holding area.




All rainwater harvesting systems have three main components: the
supply (Rainfall), the demand (Plant Water Requirement), and the
system that moves water to the plants (Water Collection and
Distribution System) . Water harvesting systems can be divided into Simple
and Complex systems. In general, simple systems immediately distribute
rainwater to planted areas, whereas complex systems store some or all of the
rainwater in a container for later use.

Rainfall. Rainwater "runoff" refers to rainwater that flows off a surface. If
the surface is impermeable, runoff occurs immediately. If the surface is per-
meable, runoff will not occur until the surface is saturated. Runoff can be
harvested (captured) and used immediately to water plants or stored for
later use. The amount of rain received, its duration and intensity all affect
how much water is available for harvesting. The timing of the rainfall is also
important. If only one rainfall occurs, water percolates into the dry soil until
it becomes saturated. If a second rainfall occurs soon after the first, more
water may run off because the soil is already wet.

Plant Water Requirements. The type of plants selected, their age and size,
and how closely together they are planted all affect how much water is
required to maintain a healthy landscape. Because rainfall is scarce in arid
regions, it is best to select plants with low water-use requirements and to limit
planting densities to reduce overall water need. Native plants are well-adapted
to seasonal, short-lived water supplies, and most desert-adapted plants can
tolerate drought, making them good choices for landscape planting.

Water Collection and Distribution Systems. Most people can design a
rainwater collection and distribution system to meet the needs of their exist-
ing site. Designing a system into new construction allows one to be more
elaborate and thorough in capturing and routing rainwater. In the case of
very simple collection and distribution systems, the payback period may be
almost immediate.



Simple system— roof catchment, gutters,
downspouts, and french drain.



RAINWATER HARVESTING



SIMPLE RAINW ATER HARVESTING SYSTEMS



SIMPLE RAINW ATER
HARVESTING SYSTEMS




Crescent-shaped landscape holding
areas on a slope.



A simple water harvesting system usually consists of a catchment, a
distribution system, and a landscape holding area, which is a con-
cave or planted area with an earthen berm or other border to retain
water for immediate use by the plants. A good example of a simple water
harvesting system is water dripping from the edge of a roof to a planted area
or diversion channel located directly below the drip edge. Gravity moves the
water to where it can be used. In some cases, small containers are used to
hold water for later use.

Catchments. A catchment is any area from which water can be collected,
which includes roofs, paved areas, and the soil surface. The best catchments
have hard, smooth surfaces, such as concrete or metal roofing material. The
amount of water harvested depends on the size, surface texture, and slope of
the catchment area.

Distribution Systems. These systems connect catchments to the landscape
holding areas. Distribution systems direct water flow, and can be simple or
sophisticated. For example, gutters and downspouts direct roof water to a
holding area, and gently sloped sidewalks distribute water to a planted area.
Hillsides provide a perfect situation for moving water from a catchment to a
holding area. Channels, ditches, and swales (shallow depressions) all can
be used to direct water. ( If desired, these features can be lined with plastic
or some other impermeable material to increase their effectiveness and to
eliminate infiltration in areas where it isn't wanted.) Elaborate open-channel
distribution systems may require gates and diverters to direct water from one
area to another. Standard or perforated pipes and drip irrigation systems can
be designed to distribute water. Curb cutouts can channel street or parking
lot water to planted areas. If gravity flow is not possible, a small pump may
be required to move the water.

Landscape Holding Areas. These areas store water in the soil for direct
use by the plants. Concave depressions planted with grass or plants serve as
landscape holding areas. These areas contain water, increase water pene-
tration into the soil, and reduce flooding and erosion. Depressed areas can
be dug out, and the extra soil used to form a berm around the depression.
With the addition of berms, moats, or soil terracing, flat areas also can hold
water. One holding area or a series of holding areas can be designed to fill
and then flow into adjacent holding areas through spillways (outlets for sur-
plus water).



RAINWATER HARVESTING



SIMPLE RAINW ATER HARVESTING SYSTEM DESIGN & CONSTRUCTION



SIMPLE RAINW ATER
HARVESTING SYSTEM DESIGN
& CONSTRUCTION




Site plan showing drainage patterns and
landscape holding areas (aerial view).




Tree dripline and basin edge.



FREE XERISCAPE GUIDE

The City of Albuquerque and
the New Mexico Office of the
State Engineer offer a free,
full-color How-to Guide to
Xeriscaping that contains many
examples of low-water use,
drought-tolerant plants. To
request your copy call 768-
3655 (Albuquerque residents),
or 1-800-WATERNM (all others).



Step #1. Design the Collection and Distribution System.

By observing your landscape during a rain, you can locate the existing
drainage patterns on your site. Use these drainage patterns and gravity flow
to move water from catchments to planted areas.

If you are harvesting rainwater from a roof, extend downspouts to reach
planted areas or provide a path, drainage, or hose to move the water where
it is needed. Take advantage of existing sloped paving to catch water and
redistribute it to planted areas. The placement and slope of new paving can
be designed to increase runoff. If sidewalks, terraces, or driveways are not
yet constructed, slope them 2 percent (1/4 inch per foot) toward planting
areas and use the runoff for irrigation. Soil can also serve as a catchment by
grading the surface to increase and direct runoff.

Step #2. Design Landscape Holding Areas.

Next, locate and size your landscape holding areas. Locate landscape
depressions that can hold water or create new depressions where you want
to locate plants. (To avoid structural or pest problems, locate holding areas
at least 10 feet from any structures.) Rather than digging a basin around
existing plants, construct level berms or moats on the surface to avoid dam-
aging roots. Do not mound soil at the base of trees or other plants. Holding
areas around existing plants should extend beyond the "drip line" to accom-
modate and encourage extensive root systems. Plants with a well -developed
root system have a greater tolerance for drought because the roots have a
larger area to find water. For new plantings, locate the plants at the upper
edge of concave holding areas to encourage extensive rooting and to avoid
extended flooding. For both existing and new landscapes you may want to
connect several holding areas with spillways or channels to distribute water
throughout the site.

Step #3. Select Plant Material.

Proper plant selection is a major factor in the success of a water harvesting
project. Native and desert-adapted plants are usually the best choices. Some
plants cannot survive in the actual water detention area if the soil is saturated
for a long period of time, so careful plant selection for these low-lying areas
is important. Select plants that can withstand prolonged drought and pro-
longed inundation, such as native or adapted plants. If you intend to plant in
the bottom of large, deep basins, low-water use, native riparian trees may be
the most appropriate plant choice.



RAINWATER HARVESTING
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