PRIVATE WATER SYSTEMS EDUCATION SYSTEM

Determining the Yield of a Cistern (2)

To determine the yield of a cistern, two questions need to be answered:
  1. Is there sufficient rainfall to take care of the yearly demand?
  2. If so, how large must the cistern be to take care of the worst drought conditions?

Answers to the Questions (2)

Net Yield of Water for Cisterns per square foot of catchement area
  1. Multiply the daily need by 365 days to get the annual demand.
  2. From the table above, select the figure in the first column that is closest to that of the surrounding area and, and note the "water yield" per square foot for that area.
  3. Multiply gallons per square foot by the number of square feet of catchment area that is available.
  4. Compare the annual needs from step 1 with the amount of water calculated in step 3. If the need is greater than the supply, either additional or alternate sources will need to be found, or water use will need to be restricted.
  5. Determine what size cistern will be needed from the table below. If there is enough water for all water uses, multiply the daily number by the number of days maximum drought period to get the gallons of storage needed.

Capacities of various sizes of cisterns

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