What is drawdown in the context of groundwater?

Drawdown refers specifically to the lowering of the water surface in a well when water is extracted from the groundwater supply. This concept is essential in groundwater hydrology and is often a key indicator of how much groundwater is being withdrawn from an aquifer and how it affects the surrounding environment.

When water is pumped from a well, it creates a cone of depression in the water table, and as a result, the water level in the well decreases. This change in water level reflects the balance between the rate of water extraction and the rate of natural recharge to the aquifer. Understanding drawdown is crucial for resource management, as excessive drawdown can lead to issues such as reduced water quality, increased energy costs for pumping, and even land subsidence.

In the context of the other choices, an increase in water level in a river is not related to groundwater extraction, the volume of groundwater storage pertains to the overall quantity of water held within aquifers rather than the effects of pumping, and the evaporation rate from a lake does not directly relate to groundwater levels or behavior. Hence, the correct answer aligns directly with the definition and implications of drawdown in groundwater management.