Variation of snow water equivalent and streamflow in relation to the El Nino/southern oscillation

Snow water equivalent (SWE), precipitation and seasonal streamflow for selected locations throughout the western United States were related to an index of the El niño/Southern Oscillation (ENSO). The strongest relations were observed when either the summer or fall averaged Southern Oscillation Index (SOI) was correlated with the maximum SWE, winter season precipitation and streamflow during the subsequent runoff season. These results suggest that the SOI can be used as a predictor of both SWE and streamflow as early as October each year with varying degrees of confidence. The magnitude of the correlations were quite variable throughout the western U.S. with the strongest associations observed in the Pacific Northwest. During El niño events, SWE, precipitation and streamflow tend to be below normal. When the opposite condition, often called La Nina, occurs SWE, precipitation and streamflow tend to be above average. These results have some important implication in water supply forecasting.