- Water Harvesting Calculations – Water Harvesting Calculations, Appendix 3 of Rainwater Harvesting for Drylands and Beyond, Vol. 1
- Rainwater Harvesting Nomogram for Tucson, Arizona – This diagram and a ruler can determine optimal sizes of rainwater tanks and/or catchment (roof) surfaces needed to meet desired amounts (in gallons) of available stored rainwater per day throughout year. What’s more, it can do the reverse — determine how much stored rainwater you can have available per day depending upon the size of your tank and/or catchment surface. Reprinted with permission from the Office of Arid Lands, University of Arizona, Tucson.
- Rainwater Harvesting Calculator for Arizona, New Mexico, and Texas Landscapes – This calculator helps estimate water needs of landscapes and potential cistern sizing based on your catchment area, water needs of plants, available water storage, and square footage of the landscape.
- Catchment Area – Runoff Calculator/Spreadsheet – Download and adapt this spreadsheet for your site’s average annual rainfall and/or surface material. Use as a dynamic computer spreadsheet or print out a hard copy to use as a quick reference guide for estimating runoff from variously sized catchments. Note that the spreadsheet default is a 90% runoff coefficient, meaning 90% of the rain falling on the catchment will run off. The other 10% will be lost to evaporation, wind, leaks, infiltration into the catchment surface, etc. This is typical for an asphalt or concrete roof or hardscape such as a patio, road, or driveway. You can change the runoff coefficient in Excel for different catchment surfaces if needed. (Metal: 95%; Concrete/Asphalt: 80-95%; Tar Roof: 85%; Sonoran Desert Uplands: 20-70%; Bare Earth: 20-75%; Grass/Lawn: 5-35%; Gravel: use coefficient of material below gravel)
July 9, 2009 by permaculturepower