Which factor can lead to water quality deterioration after over-extraction of groundwater?

Over-extraction of groundwater can lead to increased salinity levels, which is a significant concern for water quality. This occurs primarily due to the phenomenon known as "saltwater intrusion." When groundwater is extracted at a rate that exceeds its natural recharge, particularly in coastal areas, seawater can begin to move into the freshwater aquifers. The process not only raises the salinity of the groundwater but can also render it unsuitable for drinking and agricultural purposes.

Moreover, as the water table drops from excessive pumping, it can expose deeper, saline layers of soil and rock, contributing further to the salinization of the water source. Therefore, the connection between groundwater over-extraction and increased salinity levels is well-established, highlighting a critical aspect of how human activities can adversely affect water quality.

Options relating to lower temperatures, higher oxygen concentration, and increased vegetation growth do not directly link to the negative impacts of groundwater over-extraction in the same way. Lower temperatures tend to have negligible effects on salinity or water quality in the context of groundwater. Higher oxygen levels generally indicate better water quality, and increased vegetation growth tends to rely on adequate water availability, which may not be sustainable with over-extraction. Thus, these factors do not accurately explain the deterioration in water