Well Yield

Conducting well yield tests allows an operator to evaluate the efficiency and performance of a well.”

Well yield refers to the measurement of the amount of water a well can produce. Basically, well yield determines the balance between the maximum amount of water that can be pumped out of a well and the amount of water that recharges back into the well from the surrounding groundwater source. Accordingly, well yield is the volume of water per unit of time discharged from the well and is usually recorded as gallons per minute (gpm) or gallons per day (gpd).

Determining well yield requires continuous pumping of the well for an extended period of time. During the pumping period, record the rate at which water is pumped out of the well and the distance the water level in the casing drops as a result of the pumping (drawdown). Drawdown data can be combined with well yield to evaluate the efficiency and performance of a well. If the water level within the well continues to drop to the level of the submersible pump’s intake without stabilizing, drawdown from the well is exceeding the recharge rate of the aquifer. If this happens, the pumping rate is excessive and must be reduced, or damage to the submersible motor is likely, or air could be drawn into the pump.

Accurate drawdown measurements can be used with well yield data to determine if the submersible pump needs repair, or to detect an obstructed well screen.

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