Water Quality Effects of Prescribed Fire

Effects of prescribed fire on water quality vary, depending on fire intensity, type and amount of vegetation present, ambient temperature, terrain, and other factors. The major problems associated with prescribed fire and water quality are potential increases in sedimentation and, to a lesser degree, increases in dissolved salts in streamflow (Tiedemann and others 1979). However, most studies in the South indicate that effects of prescribed fire on water quality are minor and of short duration when compared with effects of other forest practices (Brender and Cooper 1968). For example, when prescribed fires are conducted properly, nutrient loss and stream sedimentation are likely to be minor compared with those resulting from mechanical methods of site preparation (Douglass and Goodwin 1980, Douglass and Van Lear 1982, Ursic 1970). Even intense broadcast burns may disturb the root mat very little, leaving its soil-holding properties intact. Furthermore, slash tends to be randomly distributed over logged areas and is seldom completely removed by broadcast burning. Therefore, the root mat, residual forest floor materials, and incompletely consumed slash form debris dams that trap much of the sediment moving downslope (Dissmeyer and Foster 1980).  Also rapid regrowth in the South quickly protects sites. Only a few studies in the South have documented the effects of prescribed fire on nutrient concentrations in streams or ground water. Low-intensity prescribed fire had no major impact on stormflow or soil-solution nutrient levels (Douglass and Van Lear 1982, Richter and others 1982). Severe wildfire in heavy fuels in mountainous terrain had no adverse effects on water quality (Neary and Currier 1982). Research from Western States documented several cases where slash burning increased nitrate-N levels in streamflow. In no case, however, did burning cause nitrate-N levels to exceed the recommended U.S. Environmental Protection Agency standard of 10 parts per million for drinking water. Phosphorus and major cations often increased in streamflow and the soil solution, but the effects were of short duration and of a magnitude not considered damaging to surface water or site productivity (Tiedemann and others 1979).