What does specific capacity measure in relation to wells?

Specific capacity is defined as the rate at which water can be discharged from a well for each unit of drawdown, typically expressed in gallons per minute per foot of drawdown (gpm/ft). This measure is crucial in evaluating the performance of a well, as it provides insight into how effectively water can be extracted relative to the decrease in water level (drawdown) within the well.

Understanding specific capacity allows hydrogeologists and water resource managers to assess the sustainability of a well, predict how it will respond under pumping conditions, and determine whether it can meet the water demands placed on it. It helps in comparing the performance of different wells and is vital for designing efficient groundwater extraction systems.

The other options do not relate directly to the concept of specific capacity. The total yield of water from a river pertains to surface water flow, volume of water per unit area could refer to water levels but not specifically to well performance, and the pressure of groundwater relates to hydraulic head but does not provide the specific measure that capacity does. Thus, the choice reflecting the rate of discharge per unit of drawdown aligns perfectly with the definition and importance of specific capacity in groundwater management.