Snowmelt contributions to flooding in the Lake Tahoe Basin

Lake Tahoe receives national attention for its declining water quality and the massive public investments in attempts to halt and reverse that decline. Much of the nutrient and pollutant load is delivered to the lake during large runoff events. This paper attempts to contribute to the understanding of those larger events by describing the flood history from the record of gaged tributaries to the lake and the mechanisms of large-flow generation in the Lake Tahoe basin. Although snowmelt runoff every spring produces significant flows of long duration, the mid-winter rain-on-snow events cause the highest peaks. Because the lower extent of the tributary catchments is the lake at an elevation of about 1900 m, only the warmest storms produce substantial rainfall in the basin. Nevertheless, some of these storms have generated massive amounts of runoff and sediment. In most cases, the snow cover influenced the release of water to streams without adding much volume from melt. However, there were a few notable exceptions with significant snowmelt.