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o~n:~~ OVERVIEW 1990 WATER SUPPLY AND OUTLOOK FOR 1991 Water resources projects in the Bureau of Reclamation are separated into five regions: Pacific Northwest, Mid-Pacific, Lower Colorado, Upper Colorado, and Great Plains (see frontispiece map), The following discussion summarizes 1990 water supply conditions-including soil moisture, snowpack, accumulated reservoir inflow, and reservoir storage--by regions and, where appropriate, provides a preliminary projection of 1991's water supply under potential streamflow scenarios, Pacific Northwest Region The Pacific Northwest Region includes the States of Washington, Idaho, and Oregon and portions of Wyoming and Montana, The region encompasses the drainage basins of the Columbia River and coastal Oregon and Washington rivers, Water Year 1990 Soil moisture conditions indicated normal to mild drought at the beginning of the 1990 water year for most of the region, Improvement was indicated for parts of the region in mid-winter, but, by the end of the water year, conditions had degraded to an extreme drought situation for about half of the region, Overall, soil moisture indicated much worse conditions for the region at the beginning of water year 1991 than at the beginning of the previous (1989) water year, Snow accumulation in the region's river basins was below normal throughout the snowfall season, The areas most affected by low snowfall were the Oregon river basins where snow accumulation was less than 50 percent of normal for most areas, One exception was the South Fork Flathead River in northwestern Montana, where the snowpack was in the normal range on May 1, 1990, Accumulated reservoir inflow ranged from wen below normal to wen above normal throughout the region by December 31, 1989, with the worst conditions in the Boise and Payette Rivers basins in western Idaho and the best conditions on the South Fork Flathead River in northwestern Montana, Generally, conditions neither improved nor deteriorated overall throughout the water year; however, some degradation in conditions occurred in the Boise and upper Snake Rivers basins in southwestern Idaho, The region started the 1900 water year with a wide range of storage conditions-from well below normal in the Snake and Boise Rivers basins in Idaho, the Yakima River basin in Washington, and the Flathead River basin in Montana, to well above normal in the Malheur and Umatilla Rivers basins in 3