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<br />. <br /> <br />soils and groundwater seepage into the rivers. The magnitude of flows was not <br />exceptionally high but the duration of the flows was longer than expected, From <br />the beginning of the melt, February 22nd, to the end of the melt, May 1", <br />Jamestown Reservoir received approximately 55,500 acre-feet of runoff. This <br />represents around 0.8 inches of runoff over a drainage area of 1300 square miles. <br />For this same period, Pipestem Reservoir received approximately 36,600 acre-feet <br />of runoff. Over a drainage area of 594 square miles this represents around <br />1.2 inches of runoff. Pipestem always produces more runoff per unit of drainage <br />area than does Jamestown. This is a result of steeper drainage gradients in <br />Pipestem's drainage basin. Jamestown's drainage is considerably flatter. This is a <br />large amount of runoff when the water equivalency of the snow pack was at the <br />most in the 1 to 2 inch range. <br /> <br />. <br /> <br />An updated forecast presented at a James River operations meeting on <br />April 7'h indicated runoff would be approximately 1 80% of normal and the <br />Jamestown pool would rise to a level very close to the 1440 ft-msl elevation that <br />would require a release of 750 cfs, At the April 7th meeting alternative operating <br />plans were discussed including a high early release followed by a low constant <br />release. There was no strong preference concerning the release schedule, so <br />releases were made according to the 1975 Field Working Agreement (FWA). <br /> <br />A release of 450 cfs as indicated in the 1975 FWA was made on April 1"' <br />after the James River at Lamoure, North Dakota, crested on March 28'h and the <br />downstream channel was clear of ice. This release was maintained until July 10'h <br />when both flood pools were completely evacuated and releases were reduced. A <br />deviation was granted on May 29th to allow Pipestem releases to be increased to <br />350 cfs and Jamestown releases to be reduced to 100 cfs. This deviation was to <br />lower the Pipestem pool elevation, facilitating construction of a relief well outflow <br />network below the dam. The deviation lasted only a week before it was agreed to <br />postpone the Pipestem contract until the drier fall months. <br /> <br />. <br /> <br />Table 13 presents a chronology of the 1998 operation of Jamestown and <br />Pipestem Dams. Figures 10 through 1 2 represent graphical summaries of reservoir <br />conditions during the 1998 runoff. Figure 13 shows the actual vs. unregulated <br />annual flow of the James River at the Jamestown gage for 1998. Figure 14 <br />represents the historical annual flow of the James River at the Jamestown gage. <br /> <br />~ <br /> <br />51 <br />