Second Page

KEY VOCABULARY

Catchment

A catchment, which may also be referred to as a watershed or drainage area, is the physical boundary in which precipitation that falls will all flow to the same drainage point. For the purpose of the CSM catchments are used to break up the roof area by determining what sections of the roof flows in a particular downspout.

Downspouts

Downspouts are the conduit (eg. Pipe) that carries water down to the ground from the gutter or scupper attached to the roof. It may also be referred to as a leader.

Rainwater Harvesting

Rainwater Harvesting is defined as "the process of intercepting stormwater runoff from a surface (e.g., roof, parking area, land surface) and putting it to beneficial use" (City of Tucson 2003). While numerous variations of this definition exist, there are elements common to most definitions - mainly that rainwater harvesting is a method to induce, collect, store, and conserve local rainfall runoff (Boers and Benasher 1982) for later re-use.

OTHER FACTORS TO CONSIDER

It should be noted that the model functions under the assumption that the user is already retaining the rainwater that naturally falls on your landscape. In some cases this may mean modifying your existing landscape with berms and basins to utilize passive rainwater harvesting to detain water onsite. Passive rainwater harvesting consists of using earthworks to slow and detain water flow on your landscape. This is usually the least expensive form of water harvesting and a good place to start your water harvesting project.

Additionally the model also assumes the user's house had gutters and downspouts to collect the precipitation. Before starting a cistern based water harvesting project (commonly referred to as active rainwater harvesting) it would be necessary to have these components installed.

Structures on the property, particularly those not connected to the house such as separate garages or sheds, can be utilized to further your water harvesting efforts. For calculation purpose the simple house worksheet can be used and entered into the CSM.

In the situation the users home has a flat roof it should be inspected by the user to see if it any ridges or structures on the roof affect drainage direction. If none exist that the user can assume that the water divides evenly between the downspouts and create catchments based on that assumption.

If questions about landscape description class arise numerous resources exist to help users determine the best estimate of what class to place the vegetations in. Your local greenhouse, the Internet and guidance manual are all excellent sources. For this model the demand values and classifications are based on the Guidelines for Landscape Drip Irrigation Systems (Arizona Landscape Irrigation Guidelines Committee July 2001).

SOURCES CITED

Arizona Landscape Irrigation Guidelines Committee (July 2001). Guidelines for Landscape Drip Irrigation System, Appendix J: 52-54.

Boers, T. M. and J. Benasher (1982). "A Review of Rainwater Harvesting." Agricultural Water Management 5(2): 145-158.

City of Tucson (2003). City of Tucson Water Harvesting Guidance Manual. A. A. Phillips. Tucson, City of Tucson, Department of Transportation, Stormwater Section.

ADDITIONAL WATER HARVESTING RELATED SOURCES

American Rainwater Catchment System Association (See http://www.arcsa-usa.org)

Forgotten Rainwater: Rediscovering Rainwater Harvesting (See http://www.forgottenrain.com/index.html)

Harvesting Rainwater for Landscape Use (See http://ag.arizona.edu/pubs/water/az1052)

International Rainwater Catchment Systems Association (See http://www.ircsa.org)

Oasis Design (See http://www.oasisdesign.net)

Rainlog (See http://www.rainlog.org)

Rainwater Harvesting for Drylands. Volume 1: Guiding Principles (See http://www.harvestingrainwater.com)

Rainwater Harvesting: Solution to Water Crisis (See http://www.rainwaterharvesting.org/)