Fire Effects on Hydrological Processes of Dryland Regions

Abstract

Hydrologic processes are affected by a fire through changes in the components of the hydrologic cycle. Impacts on the on-site components of the cycle are dependent on the pre-fire condition of the watershed burned; the intensity, severity and duration of the fire experienced; and the extent of the area burned by the fire. Reductions in interception storage, infiltration, and evapotranspiration (ET) losses lead to less soil water storage and increased overland flows of water and movement of soil on hillslopes. Off-site impacts of a fire can include increases in streamflow discharge, peak flows, and sedimentation. The physical, chemical, and biological characteristics of post-fire streamflow can also be altered, with constituents increasing, decreasing, or remaining unchanged. In terms of cumulative effects, a wildfire can produce" substantial effects" on the nature of hydrologic processes of both small stream systems and larger rivers. Cumulative effects of a prescribed burning treatment are usually less in magnitude than those following a wildfire. Key words: Fire effects, hydrological processes, off-site impacts, on-site impacts, cumulative effects.