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, , . . GVWM Flow Protection Plan 1ll\,L~ ;i~~tJDecember 19, 1994 . (.tV 4:02pm DRAFT ' ~J' X o,,\til-~ In order to determine the opportunity to conserve water 'two factors should be analyzed. First, is there need for the conserved water? An indication of need may be whether the Cameo Call) (explained on page 4) is curtailing anJ:nWtream diversions. Another indication of need may be the flow level in the IS-Mile Reach~1Cff ili~ flow in the Reach is below Fish and Wildlife Service flow recommendations then there is a need. Call this the "need" factor. The second factor is whether GVWUA is diverting excess water relative to their on-farm demand. Call this the "availability" factor. If GVWUA's on-farm demand is greater than supply then there is no excess or opportunity to conserve. There needs to be a match for both conditions to warrant changinl1lcanal operations. &~~U ~ Sorin!!: - In the spring, before significant runoff begins, the Cameo Call has occasionally required some upstream junior diverters to cease river diversions. This is a relatively rare situation happening .:::....-. times in the last ~ years. (See if I can get this info from Orlyn) If the river flows are low, it is possible for flows in the IS-Mile Reach to fall below the recommended 700 cfs minimum, but generally, this minimum is maintained. Since there is a re!TIote p.9Wbility of having a need to conserve water to supplement flows in the Reach, this {;<"''''... _:'1 'I eel' a match for the need factor. The unexpected nature of spring runoff and flows in the Grand Valley and the operational requirement to charge the canaJ system makes the question of whether excess water is being diverted rather difficult. Charging the canal involves wetting and sealing the earthen canal and flushing out debris that has collected in the canal during the winter. On-farm operations may require bringing the soil moisture up to the proper levels before planting and irrigating crops. A rather large amount of water is required to accomplish these early on-farm and offcfarm irrigation needs. Unfortunately, when river flows are low in the early spring, dry conditions are often experienced in the Grand Valley. There may be some flexibility to reduce diversions in this period but it is difficult to predict or quantify. "JIm; may be a match &If the availability factor under certain circumstances. '7'/wuI.. ZIt Summer - The benefit of a reduction in the Cameo Call during the summer is demonstrated in nearly every water year that has below average runoff, During below average runoff years a call by the Cameo group is common. This is a good match for the need factor. Analyzing spill data along the Government Highline Canal during the summer period provides an indication of whether water may be available. During the peak of the irrigation season (about I June through early- to mid-September) monitoring of water patterns over the last 2 irrigation seasons (1992 and 1993) has shown that GVWUA frequently can and does deliver and use all of the water available to their irrigation water right. This does not happen everyday throughout the summer season but does demonstrate use of their full irrigation water right. The timing and duration of these peak uses is not predictable. Therefore, it is not fq.~ible to make adjustments of diversion amounts to reflect a temporary reduction of demand wittnhe existing canal system. The possibility of saving water during this period is remote and if at all possible would require 15