How do plants help control water quality and water levels?

Plants play a critical role in regulating the hydrologic cycle by managing water storage, flow, and quality through several biological and physical mechanisms:

Water Level Regulation

• Interception: Vegetation acts as a barrier, catching precipitation on leaves and stems. This process, known as interception, allows water to evaporate directly back into the atmosphere before it ever reaches the ground.12
• Evapotranspiration: Plants absorb water from the soil through their roots and release it as water vapor through their leaves via transpiration. This process, combined with soil evaporation, is called evapotranspiration and is a primary way plants reduce soil moisture and regulate the water table.12
• Flood Mitigation: By slowing the movement of water across the landscape, plants prevent the rapid runoff characteristic of barren land. This helps maintain more uniform, reliable streamflow and reduces the risk of sudden flooding.1

Water Quality Control

• Natural Filtration: Forests and their associated soil and litter layers act as effective filters. As water moves through these systems, plants and soil help purify it, resulting in water that is typically high in oxygen and low in temperature and foreign substances.1
• Erosion Protection: Plant cover protects soil from erosion, which is a major cause of water-quality degradation. By stabilizing the ground, vegetation prevents sediment and suspended solids from entering waterways.1