Yield and Specific Capacity

Yield and specific capacity are two terms that relate to the measurement of the amount of water a well can produce. Yield is generally expressed in Gallons Per Minute (GPM). Specific capacity is determined by dividing the yield by the drawdown. The resulting number is expressed in gallons per minute per foot. For example, if a well yields 100 GPM and it has a drawdown of 30 feet, its specific capacity at that flow rate is 3.33. By tracking the specific capacity of a well over time, an operator can identify well and aquifer performance problems.