What parameter does a pumping test estimate in an unconfined aquifer?

The correct answer is hydraulic conductivity, as a pumping test is primarily designed to measure how easily water can move through an aquifer material. During the test, water is pumped from a well at a controlled rate, and the change in water levels in response to this pumping is monitored in that well and surrounding observation wells.

The data collected from the pumping test analysis allows for the calculation of hydraulic conductivity, which is a measure of the aquifer's ability to transmit water. It is influenced by the material's characteristics, such as grain size and sorting. While other parameters related to aquifers, like transmissivity and specific yield, can also be derived from pumping tests, the most fundamental and directly measured aspect is hydraulic conductivity.

Transmissivity represents the total capacity of the aquifer to transmit water, and it is derived from hydraulic conductivity but takes into account the thickness of the aquifer. Porosity is related to the volume of voids in the material but is not something directly estimated through a pumping test. Specific yield is a measure of the amount of water that an unconfined aquifer can yield to wells, but again, it is not the primary output from a pumping test. Thus, hydraulic conductivity is the key parameter obtained through this process in