What is recharge in terms of hydrology?

Recharge in hydrology refers to the process by which water from precipitation or other sources infiltrates the ground and moves down through the soil and rock layers to replenish the groundwater aquifer. This process is essential for maintaining the water supply in aquifers, ensuring they remain sustainable over time.

When water infiltrates into the soil, it undergoes percolation, where it gradually moves deeper into the earth until it reaches the water table, which is the upper surface of the saturated zone in the ground. This replenishment of groundwater is crucial for various ecosystems, agricultural practices, and the availability of drinking water. By understanding recharge, hydrologists can develop better water management strategies and policies that help protect and sustain these vital resources.

The other options do not accurately define recharge; they describe different aspects of the hydrologic cycle, such as outflow, evaporation, and surface runoff.