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Table 7-$um severity classification based on postfire appearances of litter and soil and soil temperature profiles (Hungertord 1996, DeBano et al. 1998). Burn Severity Soil and Litter Parameter Low Moderate High Litter Scorched, Charred, Consumed Consumed Consumed Duff Intact, Surtace Deep Char, Consumed Char Consumed Woody Debris -Small Partly Consumed, Consumed Consumed Charred Woody Debris -Logs Charred Charred Consumed, Deeply Charred Ash Color Black Light Colored Reddish, Orange Mineral Soil Not Changed Not Changed Altered Structure, Porosity, etc Soil Temp, at 0.4 in (10 mm) X120 °F 210-390 °F >480 °F (<50 °C) (100-200 °C) (>250 °C) Soil Organism Lethal Temp. To 0.4 in (10 mm) To 2 in (50 mm) To 6 in (160 mm) occurrence of hydrologic events. For a wide range of burn severities, the impacts on hydrology and sedi- ment lose can be minimal in the absence of precipita- tion. However, when a precipitation event follows a large, moderate- to high-burn severity fire, impacts can be far reaching. Increased runoff, peakflowa, and sediment delivery to streams can affect fish popula- tions and their habitat (Rinse 1996). Fire can destroy accumulated forest floor material and vegetation, altering infiltration by exposing voile to raindrop impact or creating water repellent condi- tions (DeBano and others 1998). Loss of soil from hillsIopes produces several significant ecosystem im- pacts. Soil movement into streams, lakes, and ripar- ian zones may degrade water quality and change the geomorphic and hydrologic characteristics of these systems. Soil loss from hillslopea may reduce Bite productivity. Total water yields across the Western United States vary considerably depending on precipitation, evapo- transpiration (ET), soil, and vegetation. The magni- tude of measured increases in water yield the first year after fire can vary greatly within a location or between locations depending on fire severity, cli- mate, precipitation, geology, soils, topography, veg- etationtype, and proportion ofthe vegetation burned. Because increases in water yield are primarily due to elimination of plant cover, with subsequent reduc- tions in the transpiration component of ET, flow increases are greater in humid ecosystems with high prefire ET (Anderson and others 1976). El- evated streamflow declines through time as woody and herbaceous vegetation regrow, with this recov- ery period ranging from a few years to decades. Increases in annual water yield after wildfires and prescribed fires are highly variable (table 2). Hibbert and others (1982) reported a 12 percent increase in water yield after prescribed fire in an Arizona pinyon- juniper forest. Awildfire inthe moetlyponderosa pine Entiat watershed in Washington produced a 42 per- cent increase in water yield the first poatfire year (Helvey 1980). The first-year increase in water yield after a prescribed burn in a Texas grassland was 1,150 percent of the unburned control watershed, but the increase over the control was only 400 percent where a rehabilitation treatment (seeding) was done after the fire (Wright and others 1982). Seeding also ahort- enedthe recovery period from 5 to 2 years. In Arizona chaparral burned by wildfire, the first-year water yield increase exceeded 1,400 percent (Hibbert 1971). Where sail wettability becomes a problem, water yield increases can be very high due to greater stormflows. The effects of fire disturbance on storm pealcflowa are highly variable and complex. They can produce some of the moat profound watershed and riparian impacts that forest managers have to consider. In- tense short duration storms that are characterized by high rainfall intensity and low volume have been associated withhigh stream peakflows and significant erosion events after fires {Newry and others 1999). In the Intermountain Weat, high intensity, short dura- tionrainfall i a rel ativelycommon (Farmer and Fletcher 1972). Five minute rainfall rates of 8.4 to 9.2 in hr_1 (213 and 235 mm hr'') have been associated with USDA Forest Service Gen. Tech. Rep. RMRS-GTR~63. 2000