Call-For-Water cycle | Well operations metrics | Aquifer metrics
Call-For-Water cycle
A call-for-water (“CFW”) is initiated when the water level in a tank or reservoir drops below a set threshold and the well pump is powered. Depending on whether the pump’s output (gpm) is greater than or less than the rate at which the aquifer refills the well, one of the sequences below occurs:
- If the pump rate exceeds the rate at which the well is refilled with water, the pump cycles on and off until the CFW ceases.
- If the pump rate is less than the refill rate, the water level in the well drops to the “drawdown” level and the pump operates continuously until CFW ceases. At the drawdown level, the rate at which water is pumped out of the well equals the rate at which the aquifer replenishes the well.
Well/aquifer metrics
Well operation metrics
Pump delay time: How long the pump relay waits after the well drains before starting the well again.
Pump rate: The pumping capacity of the pump. This is unrelated to the aquifer and only measures the pumping capacity of the pump itself.
Duration—CFS cycle: The duration of a CFW cycle.
Cumulative water pumped: Total water pumped over the CFW cycle
Aquifer metrics
Static water level: For an unconstrained well, the static water level is, effectively, the top of the aquifer. Over time, as the aquifer is drained due to extraction and refilled by natural water migration, it will move up and down.
% recovery—first/last pump cycle: How much the well refilled on the first/last pump cycle during a CFW cycle, expressed as a percentage of the static water level.
Time to refill to 95%: measures how long it takes for the well to refill to 95% of the static level after a CFW ceases. This is a simple metric that captures the aquifer’s productivity.
Sustainable yield: Water yield (gpm) that can be sustained as the CFW cycle is extended. Sustainable yield is an average pumping rate including periods when the pump is operating as well as when it is temporarily off in-between pump cycles.
Rate of refill as function of depth: After CFW, the well refills. Initially, it refills rapidly and then the refill rate slows. Ploting the rate of refill as a function of the depth of water in the well provides a vertical profile of the aquifer.
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