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f j I I I I' I , I l , I I i I I I I I BIOLOGICAL OPINION Proposed Action storage if more water arrives than is demanded, or releasing water into the river when there is not enough to meet demands. Changes to water demand may result from a change in weather (rainfall, frost warnings, wind, high temperatures, cooler temperatures, etc.), holidays, or structural failure of an irrigation facility. f. Water releases and power production The release of water through Davis and Parker Dams is subject to water orders, need to manage flood waters, and hydropower obligations. The authorizing legislation for Parker and Davis Dams required the generation of power and granted exclusive rights of the facility's power capacity and energy to priority-use power customers. Priority-use power customers are customers who were the first project power recipients after the project was complete; this entitlement is held in perpetuity. "Capacity" in this usage means the electrical generating capacity of on-line generator units, whether or not they are actually producing power at any specific time. The capacity and energy utilized by the Parker-Davis electric service customers is termed "firm electric service power." The users have firm capacity and firm energy contracts with the United States which are in effect until midnight, mountain standard time, September 30, 2008. Each Parker-Davis electric service contract contains essentially the same language. As an example, subsection 5.1 of Contract No. 87-BCA-10108 with Yuma Irrigation District is entitled "Western's [Western Area Power Authority] Energy and Capacity Obligations." Paragraph 5. 1. 1 of that subsection states in pertinent part: "The Contract Rate of Delivery [CROD] will be available in any hour within the billing period." This means that if the "firm" electric service customer requests a capacity within its minimum seasonal CROD, at any hour, and water is available to supply that capacity, the United States is obligated to make the power resource available (that is, put the generator units on-line and release the water through them). The scheduling and subsequent release of water through Davis and Parker Dams affect daily fluctuations in river flows, depths, and water surface elevations downstream of these structures. Typical seasonal flow patterns are illustrated for representative gauging locations on the LCR (Figs. 6 through 10). (The location of the representative gauging stations are shown in Fig. 5, above; their names and distance, in miles, from the SIB are: Davis Dam, 275.4; Parker Dam, 192.2; Water Wheel, 152; Taylor Ferry, 106.6; and below Cibola Valley, 87.3. Typical seasonal flows, in cfs, and water surface elevations, in feet msl, are shown for each of the five stations.) Figs. 6 and 7 demonstrate that the water surface elevation fluctuates most noticeably in the river reaches closest to the dams. The magnitude of the fluctuations diminish as the distance downstream increases, as shown in Figs. 9 and 10. The Mohave Valley and Parker Divisions of the river are most affected by fluctuations on a daily basis. The Imperial, Laguna and Yuma Divisions are the least affected, being farther downstream from the dams. The river fluctuates seasonally with the highest water levels occurring during the summer and the lowest water levels 19