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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />l,. '1,.' ~ <br />002355. <br /> <br />the water required by Mexico and United States users downstream of Parker Dam and system <br />losses resulting from transporting the water from Parker Dam to Imperial Dam. <br /> <br />When either more or It(ss water than needed by United States entitlement holders arrives at <br />Imperial Dam, storage ibehind Imperial Dam, Laguna Dam, and Senator Wash Dam is <br />utilized to attempt to regulate incoming Colorado River flows in order to meet actual water <br />demand and prevent o~er deliveries of water to Mexico. Regulating flows involve either <br />pumping water into sto~ge if more water arrives than is demanded or releasing water into <br />the river when there is i not enough to meet demands. Changes to water demand may result <br />from a change in weather (rainfall, frost warnings, wind, high temperatures, cooler <br />temperatures, etc.), holidays, or structural failure of an irrigation facility. <br /> <br />I <br />Normal operational vaIjiances in elevation at Imperial Dam are from 180 feet to 180.9 feet <br />msl. The top of the sp~llway at Imperial Dam is approximately 181 feet; this elevation is <br />seldom exceeded. If ~ater demand exceeds flows arriving at Imperial Dam for extended <br />periods, the elevation ~ehind Imperial Dam may, on very rare occasions (1 to 3 times per <br />year), be drawn down ~o elevation 178.5 feet. This elevation would not be maintained for <br />more than a few days. i Elevations of the reservoir above Imperial Dam continuously <br />fluctuate, to some degr~, daily and during the day. Fluctuations are due to variability in the <br />flows arriving at the dam and water entitlement holders' demand changes. <br /> <br />Normal operational variances in elevation at Laguna Dam are from 138 feet to 151.3 feet <br />msl. The top of the sp~llway at Laguna Dam is elevation 151.3 feet msl. The maximum <br />elevation is met a few times a year when the storage is used to prevent or reduce over <br />I <br />deliveries to Mexico. The lower elevations occur when it is necessary to use the water <br />stored in Laguna ReserVoir to meet Mexico's water order. This normally occurs when water <br />demand has increased cifter releases have already been made from Parker Dam. Elevations <br />behind Laguna Dam continuously change due to the continuously changing water demand at <br />Imperial Dam. <br /> <br />Normal operational vaQances in elevation at Senator Wash reservoir are from 210 feet to <br />240 feet msl. The reservoir is currently on an elevation restriction at 240 feet msl for safety <br />concerns regarding seepage above that level. Prior to the elevation restriction of 240 feet <br />msl, the normal range in elevation was from 210 feet to 251 feet msl (the top of the <br />spillway). Several potential repairs for Senator Wash which could allow full utilization of its <br />storage capacity are un~er current review, but it will be a number of years before repairs can <br />be accomplished. The reservoir elevation is continually fluctuating because Senator Wash is <br />used to regulate flows arriving at Imperial Dam. <br /> <br />Flows arriving at ImpeJjal Dam normally range from a high of about 14,400 cfs (which <br />usually occurs in late spring to summer) to a low of about 2,500 cfs (which usually only <br />occurs after a heavy loCal rainfall over the entire area below Imperial Dam, usually <br />November or December, and when water entitlement holders are not taking water). <br />Mexico's water order has to be delivered regardless of excess rainfall. <br /> <br />48 <br />