What natural process can negatively affect river ecosystems when groundwater is over-extracted?

When groundwater is over-extracted, it leads to decreased groundwater recharge. Groundwater recharge is the process where water from precipitation or surface water infiltrates into the ground to replenish aquifers. This process is vital for maintaining the base flow of rivers and streams, especially during dry periods.

When the groundwater levels are lowered due to over-extraction, it diminishes the amount of water that seeps into rivers and streams, leading to reduced streamflow. This reduction can have several harmful effects on river ecosystems, such as lower water levels, higher water temperatures, and reduced habitat availability for aquatic species. Moreover, decreased groundwater recharge can disrupt the natural balance of the ecosystem by affecting the biodiversity and health of aquatic life.

Other choices do not reflect the negative consequences associated with the over-extraction of groundwater in river ecosystems. For instance, increased water flow is typically beneficial for rivers and ecosystems, while improved water quality and enhanced aquatic vegetation growth generally suggest a healthy ecosystem. However, these can be adversely affected when the base flow is reduced, but they do not directly describe the negative impact of over-extraction itself.