Summary
Highlights
Hydrological losses, also known as abstractions, reflect a watershed's ability to retain water at the beginning of a storm. When a storm follows a dry period, the ground, vegetation, and depressions are dry, creating the greatest potential for immediate storage of rainwater.
Before rain even occurs, the primary hydrological loss is the evaporation of water vapor into the atmosphere.
Once rain begins, other losses come into play. These include water intercepted by vegetation, water stored in small surface depressions, and water that infiltrates into the soil. Interception and depression storage are estimated based on factors like vegetation and ground surface, but can be negligible in larger storms.
Net runoff is calculated by subtracting total hydrological losses from precipitation. There are six main components of hydrological losses: evaporation, transpiration (together forming evapotranspiration), infiltration, and lastly, interception and depression storage.