Low streamflow conditions in the western states during 1987

Drought conditions prevailed throughout the States of California, Nevada, Idaho, Oregon, and Washington during the summer of 1987.Streamflows were the lowest since the drought of 1977.Many streams had less discharge in August-September 1987 than in August-September of 1977.At some sites flows for July, August, and September were the minimum ever recorded for those months.The reasons for the low flows, which occurred in spite of near normal precipitation for the 1987 water year (October 1, 1986 to September 30, 1987), were low winter snowpack, unseasonably early melt of that snowpack, and prolonged periods of wellabove-average temperatures.Conditions are conducive for a potentially serious drought in 1988.The low flows and a large demand for water during the summer of 1987 left many storage reservoirs at well-below-average levels.At least four cities had less than a 2-month supply of surface water at the end of September.In some areas, ground-water levels have lowered considerably, as indicated by the need to deepen irrigation wells in Oregon.Cities that used ground water did not experience serious problems in 1987 but could have extreme shortages in 1988 if groundwater supplies are not replenished.Even though the flow conditions worsened noticeably during the 1987 water year, careful management and conservative water-use practices prevented widespread critical water shortages.The U.S. Geological Survey is measuring the quantity and quality of streamflow in order to assess the extent and severity of the drought.