Specific Capacity

The specific capacity of a well is defined as the well flow per unit drop of water level in the well.

Specific capacity = — = p + pnn_1 9.9(5) st Cw + CfQ

Specific capacity decreases with the pumping rate and time as shown in Figure 9.9.2. It is a useful concept because it describes the productivity of both the aquifer and the well in a single parameter. A reduction of up to 40% in the specific capacity has been observed in one year in wells deriving water entirely from storage (Gupta 1989). The specific capacities of wells in an aquifer system can be used to calculate the transmissivity distribution of the aquifer based on pumping a well of a known diameter for a given period of time.

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