In a yield and drawdown test, what must be recorded before testing begins?

Before conducting a yield and drawdown test, it is essential to record the static water level. The static water level is the measurement of how deep the water is in the well when it is at rest, prior to any pumping. This measurement provides a baseline for understanding the starting conditions of the aquifer and is critical for determining how much water can be sustainably pumped from the well during the test.

During the testing process, the drawdown, which is the decrease in water level as the pump removes water, is compared to the static water level recorded beforehand. This comparison allows for the evaluation of the well's performance and the aquifer's characteristics, such as its yield capacity and the stability of the water supply over time. Recording this level is crucial for accurate analysis and for ensuring that the well operates within safe limits to avoid over-extraction or damage to the aquifer.

Other parameters such as pumping level, discharge rate, and recovery level are important but are assessed during or after the initial measurement of the static water level, making the static level the primary and necessary recording before test commencement.