Soil regulates the water cycle: A natural sponge and filter

Soil and Groundwater

However, not all infiltrated water is, or can be, used by plants. Water that continues to move downward through the soil profile and can recharge groundwater. Groundwater feeds springs, streams, rivers, and drinking water in many regions, highlighting the important role of soils in regulating freshwater resources.

Did you know? It is estimated that approximately 99% of the Earth's accessible freshwater is stored as groundwater, and groundwater withdrawals account for about 25% of global human water use (Pointet, 2022). Most of the extracted groundwater is used to irrigate agricultural land, while the remainder supports industrial processes and drinking water supplies (Pointet, 2022). For example, in countries within the Danube River Basin in Central and Southeast Europe, approximately 72% of drinking water is sourced from groundwater (Liska, s.a.).

The balance between water storage, plant uptake, evapotranspiration, and groundwater recharge depends on many interacting factors, including soil texture and soil structure, vegetation, climate, and land management. Soils with connected pore networks can absorb and store large amounts of water while allowing excess water to drain gradually. This reduces surface runoff and erosion during heavy rainfall while maintaining water availability for plants during dry periods. In contrast, compacted or sealed soils often allow less water to infiltrate, resulting in greater runoff, reduced groundwater recharge, and increased vulnerability to both flooding and drought.

Rather than acting as a passive container, soil regulates how water moves through landscapes. By slowing, storing, filtering, and redistributing water, soil plays a fundamental role in the terrestrial water cycle and in the resilience of ecosystems and human societies.

You may also watch the animated video “Soil Water Processes: Infiltration and Saturation” below. It illustrates how water infiltrates into dry and saturated soils. Notice how soil moisture conditions influence the rate of infiltration and the movement of water through soil. The video is only 25 seconds long and was produced by LA River Master Plan.