Snow-Covered Area Utilization in Runoff Forecasts

Long-term data on snow-covered area from aircraft and satellite observations have been investigated for application to water-supply forecasting in California's southern Sierra Nevada Mountains. These observations have proven useful in reducing seasonal runoff forecast error on the Kern River watershed when incorporated into procedures to update water-supply forecasts as the melt season progresses. Similar use of snow-covered area on the Kings River watershed produced results that were about equivalent to methods based solely on conventional data. Snow-covered area will be most effective in reducting forecast procedural error on watersheds with: (1) A substantial amount of area within a limited elevation range; (2) an erratic precipitation or snowpack accumulation pattern, or both, not strongly related to elevation; and (3) poor coverage by precipitation stations or snow courses restricting adequate indexing of water-supply conditions. When satellite data acquisition and delivery problems are resolved, the derived snow-cover information should provide a means for enhancing operational streamflow forecasts.