Long-range streamflow forecasting in the Columbia River Basin using El Niño-Southern Oscillation

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Preliminary research has shown that there is a significant relationship between western U.S. streamflow and the El Nino-Southern Oscillation (ENSO). In some regions, there is a six month lead time between the ENSO predictor and the ensuing streamflow. The Southern Oscillation Index (SOI) and the Wright Sea Surface Temperatures (SSTw) are used here to study the lag relationship between western U.S. streamflow and ENSO indices. In the southwest and northwest, the spring-summer runoff is significantly correlated with the prior summer and autumn SOI and SSTw values. These six to nine month lag correlations are important in making long-range streamflow forecasts. A long-range seasonal streamflow forecasting model is developed and tested on the Columbia River Basin, Washington State. A probabilistic streamflow forecast is made from an optimal linear combination of SOI Phase, SSTw Phase, and SOI Linear Discriminant Analysis (LDA), and SSTw LDA forecasts. The forecast takes the form of a probability of the streamflow occurring in specified categories (i.e., below normal, normal, and above normal). The optimal linear combination of the four models is the forecast that minimizes the mean square error (HalfBrier score). This final combination forecast is referred to as a "consensus forecast." This consensus model is used on seven Columbia River basin streamflow stations that cover the period 19331992. It was found that the best predictor period for spring, summer runoff, based on SOI and SSTw data, was the previous years summer, and the SOI is generally a better predictor of spring-summer runoff than SSTw. This works demonstrates the potential of using ENSO indicators for long-range streamflow forecasting in the Columbia River basin.


Columbia River Basin; Washington; El Nino-Southern Oscillation (ENSO); Long-range streamflow forecast modelling; Precipitation; Runoff; Water supply forcasting


Environmental Indicators and Impact Assessment | Environmental Sciences | Fresh Water Studies | Meteorology


Presented at the American Geophysical Union, 1997 Spring Meeting, Baltimore, Maryland, May 27-30.


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