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<br />.'n:i~ 38 <br />-" -.' v... <br /> <br />year, Overall, soil moisture measurements indicate much worse conditions for the <br />region at the beginning of water year 1991 than at the beginning of water <br />year 1990, except for the lower Rio Grande, <br /> <br />Snowpack in the river basins originating in western Colorado and southwestern <br />Wyoming was below normal to well below normal on February 1, 1990, with the <br />worst conditions located in southwestern Colorado, By May 1, conditions in <br />southwestern Colorado had improved and those in southern Wyoming had <br />degraded, but, overall, conditions remained below normal to well below normal. <br /> <br />Accumulated inflow to the region's reservoirs in the Colorado River basin was <br />below normal to well below normal throughout the year, Total inflow to Lake <br />Powell was less than 50 percent of normal. Also, accumulated inflow to Elephant <br />Butte Reservoir on the Rio Grande was less than 50 percent of normal for the <br />water year, <br /> <br />Reservoir storage was between 70 and 90 percent of capacity for reservoirs in the <br />Colorado River and Rio Grande basins at the beginning of the water year, Storage <br />conditions generally degraded for the region as the year progressed, with <br />Lake Powell (the principal storage feature in the Colorado basin) dropping from <br />79 percent of capacity to 65 percent of capacity by year's end and Elephant Butte <br />Res.ervoir on the Rio Grande dropping the s.ame percentages. through the year, As. <br />with the Lower Colorado Region, storage in this region is reported as a percent of <br />capacity, rather than as a percent of average because carryover storage is provided <br />by Lake Powell for many years at a time. The average for a particular time of the <br />year is not as meaningful as it is for a reservoir that provides carryover storage on <br />an annual cycle. <br /> <br />The runoff into Lake Powell during water year 1988 was approximately 70 percent <br />of normal; in water year 1989, runoff was approximately 53 percent of normal; and <br />in water year 1990, runoff was approximately 46 percent of normal. The low <br />runoff years of 1988, 1989, and 1990 have caused a drawdown in each of the <br />Colorado River system reservoirs. The vacant s.pace on October 1, 1990, in the <br />mainstem reservoirs, was about 16.7 miJlion acre-feet, The vacant space has <br />resulted from the three s.uccessive years oflow inflow while maintaining the <br />minimum deliveries of water out of storage facilities to meet obligations pursuant <br />to "The Law of the River," <br /> <br />An abundance of mid-summer moisture in the Rio Grande Valley resulted in lower <br />us.e of res.ervoir s.torage for the 1990 irrigation season than was. predicted on <br />March 1, 1990, SmaJler projects generaJly used the predicted amount of reservoir <br />storage, and they wiIl need normal to above normal conditions to add water in <br />storage in 1991. In general, conditions improved slightly over early forecasts. as. <br />the seas.on progressed. <br /> <br />Inflow to Elephant Butte Reservoir for 1990 for the March through July forecast <br />period was 165,000 acre-feet, or 34 percent of normal. Inflow for water year 1990 <br /> <br />9 <br />