What is an undesired effect of excessive groundwater extraction?

Excessive groundwater extraction can lead to land subsidence, which is the sinking or settling of the ground surface. This occurs because the removal of a large volume of water from the underground aquifers reduces the pressure that supports the soil and rock layers above. When the water is drawn out faster than it can be replenished, the voids that were filled with water are often replaced with air, leading to the compaction of the ground materials. As a result, the land can begin to sink, which may cause damage to structures, roads, and infrastructure, and can disrupt natural drainage patterns.

In contrast, increased water table levels, while they may initially seem beneficial, are not a common undesired effect of excessive extraction; rather, they typically occur when groundwater replenishes adequately. A reduction in water quality can happen, but it is often a secondary effect related to other concerns such as contamination or increased salinity rather than directly from excessive extraction itself. Improved agricultural yields are generally associated with adequate or improved water availability, not excessive extraction, which can lead to negative long-term consequences for farming. Thus, land subsidence is a direct and significant undesired effect of excessive groundwater extraction.