Drawdown in Pumping Out Test

In a pumping out test, the drawdowns are observed at a number of wells. This test is conducted to determine the yield and efficiency of a well or a group of wells. The following are the details of the pumping out test:

Procedure:

1. A well is pumped at a constant rate, and the water level is measured at a number of observation wells located at different distances from the pumping well.

2. The water level in each observation well is measured several times during the test, and the drawdown corresponding to each measurement is recorded.

3. The test is continued until the water level in the pumping well stabilizes, and the drawdown at the observation wells reaches a constant value.

4. The data obtained from the test is used to plot a drawdown-time curve, which is used to determine the yield and efficiency of the well.

Interpretation:

The drawdown-time curve obtained from the pumping out test provides information about the hydraulic properties of the aquifer. The following are the interpretations that can be made from the curve:

1. The yield of the well can be determined from the maximum drawdown observed during the test.

2. The efficiency of the well can be determined from the slope of the curve during the early part of the test.

3. The hydraulic conductivity of the aquifer can be determined from the shape of the curve and the distance between the pumping well and the observation wells.

Conclusion:

The pumping out test is an important tool for determining the yield and efficiency of a well or a group of wells. The drawdowns observed at the observation wells provide valuable information about the hydraulic properties of the aquifer, which can be used to optimize the design and operation of the wells.