Regional hydrologic variability and the El Niño-Southern Oscillation

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In the past decade, there has been an increased awareness of the relationship between the El Nino-Southern Oscillation (ENSO) and streamflow in various regions of the Pacific Rim. In this work, results are presented on the relationship between ENSO and streamflow variability in Canada, the Western United States, and Australia. In the Western U.S., the strongest responses to ENSO are seen in the Pacific Northwest where a strong relationship exist between El Nino and extreme droughts. In a 94-year period from 1900 to 1993, the three largest droughts occurred in the year after a El Nino event. In Canada, the Western and Central portions experience below normal streamflow in the year after an El Nino event. In Australia, ENSO indicators can be used to help forecast spring runoff in the Southeast and summer runoff in the Northeast and East coasts of Australia. The potential of making seasonal long-range streamflow forecast is also examined using two ENSO indicators ? the Southern Oscillation Index (SOI) and the Wright Sea Surface Temperatures (SSTw). A probabilistic streamflow forecast model is developed that uses Linear Discriminant Analysis (LDA) to find the probabilities of streamflow occurring at various levels. The impetus for this model is a study that Australian Bureau of Meteorology has used for making seasonal precipitation outlooks. Preliminary results of seasonal streamflow forecasting in Eastern Australia indicate that the model has the best overall skill during the times of highest runoff. A modified version of the seasonal streamflow forecast model is used to make streamflow forecasts of spring-summer runoff in the Columbia River basin located in the Pacific Northwest United States. It was found that three- to seven-month lead time forecasts of spring-summer runoff, based on the SOI and SSTw, had better skill than the Climatology forecast. Future work will evaluate the benefits of using ENSOstreamflow forecast for the optimal operation of reservoir systems.


El Nino-Southern Oscillation (ENSO); Long-range streamflow forecasting; Precipitation; Streamflow; Water supply forcasting


Environmental Monitoring | Environmental Sciences | Fresh Water Studies | Meteorology


Presented at the American Geophysical Union, 1998 Spring Meeting, Boston, Massachusetts, May 26-29 (INVITED).


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