Which environmental problem is primarily associated with excessive groundwater extraction?

Excessive groundwater extraction is primarily associated with land subsidence. This phenomenon occurs when water is withdrawn from the ground at a rate faster than it can be replenished. As groundwater levels fall, the support that the water provides to the soil is reduced, leading to the compaction of soil layers. Over time, this compaction can cause the land above to sink, resulting in land subsidence.

Land subsidence can have significant consequences, including damage to infrastructure, increased flood risk in certain areas due to altered land elevation, and changes to natural drainage patterns. The other options, while related to groundwater issues, do not specifically arise from excessive extraction in the same direct manner. For example, saltwater intrusion typically occurs in coastal areas where excessive groundwater extraction allows saltwater to encroach into freshwater aquifers. Groundwater contamination can result from various sources, including agricultural activities and industrial discharges, which are not directly linked to extraction rates. Flooding, on the other hand, is generally associated with surface water runoff and heavy rainfall rather than groundwater extraction.