Use of Long-Range Exceedance Probability Forecasts in Management of Water Resource Systems

The El Niño-Southern Oscillation is used here as a basis tor long-range exceedance probability forecasts that have the potential for improving the management of water resource systems in eastern Australia and the western United States. An exceedance probability forecast is important for the design and operation of water resource systems, that require a high degree of system reliability. Past studies have shown that the hydrology in these regions is strongly effected by ENSO. The relationship is strong enough to develop a seasonal streamflow forecast in both of these regions. In eastern and south-eastern Australia, there is a strong tendency for below normal hydrologic conditions following an El Niño event. In the western U.S., the potential of making a six-month lead time forecast of spring-summer runoffis demonstrated for the Columbia River basin. The skill associated with these forecasts is better than the baseline "climatology" condition and the potential benefits of using these forecasts in the management of water resource systems is explored. For instance, the potential benefits of using these forecast are demonstrated for an urban water supply system and for a rural irrigation system in eastern Australia.