Intensification of the hydrological cycle could make reservoir management more challenging, since there is often a tradeoff between storing water for dry-period use and evacuating reservoirs prior to the onset of the flood season to protect downstream communities. It may become more difficult to meet delivery requirements during prolonged periods between reservoir refilling without also increasing the risk of flooding. Earlier spring runoff from snowmelt is a likely manifestation of global warming. Much of Europe and the western United States depend on snowmelt as a water source for most of the year, so earlier runoff clearly affects water storage on a broad scale. To the extent that adequate reservoir space is available, changes in reservoir management practices could mitigate some of these effects. Seasonal climate forecasts might provide some adaptation leverage for reservoir managers. For example, forecasts based on the current state of the El Niño-Southern Oscillation and other large-scale climatic indices correlate well with precipitation patterns in some regions, and would be useful information for reservoir management decisions.