If a well has a drawdown of 27 feet and a theoretical drawdown of 18 feet, what is the well efficiency?

To determine the well efficiency, you can use the formula:

[ \text{Well Efficiency} = \left(\frac{\text{Theoretical Drawdown}}{\text{Actual Drawdown}}\right) \times 100% ]

In this case, the actual drawdown is 27 feet, and the theoretical drawdown is 18 feet. Plugging the values into the formula gives:

[ \text{Well Efficiency} = \left(\frac{18}{27}\right) \times 100% = 0.6667 \times 100% = 66.67% ]

Rounding to the nearest whole number, this results in an efficiency of approximately 67%. This indicates how effectively the well is producing water compared to the theoretical maximum output based on its design and surrounding conditions. A higher efficiency percentage implies that the well is performing closer to its expected capacity.