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. .... ...... lq'J::; Table 3 DIVERSIONS MINUS MEASURED RETURNS FOR MAJOR WATER USERS LOWER COLORADO RIVER 1966 to 1970 (Thousands of Acre-Feet) Water r~8r Clhfornia Metropolitan Water Dist. ........................ Palo \'erde Irrig. Dist. ........................ Imperial Irrig. Dist. Coachella \'alley Co. Water Dist. Yuma Project, Reser\'. Di.... ... 1966 /96i 1968 1969 1970 1,121 1,182 1,105 1,139 1,205 384 365 387 386 384 2,778 2,860 2,745 2,766 2,751 484 453 469 490 448 48 53 56 65 48 4,815 4,911 4,762 4,846 4,836 Total J Deliveries to Mexico The Bureau of Reclamation maintains a control schedule which includes the sche- duled deliveries to Mexico plus releases from storage for sluicing, river regulation, and other purposes. The scheduled deliveries, control schedule amounts, and excess deliv- eries to Mexico for recent years are shown in Table 4. r Table 4 DELIVERIES TO MEXICO COLORADO RIVER SYSTEM (Thousands of Acre-Feet) Water Y~ar Sch.dul.d Deliv~ri~s to Control M~xit:O" Sch~u/~ Flow to M~xico Exc~ss Ddi~'~ri~s ro Mexico Excess Ov~r Control Sch~u/~ Arizona Colorado Ri.... Indian Reser.... ........ Gila Project ................ Yuma Project, \'alley Di.... 1962 .... 1,500 1,540 1,763 263 223 1963 ......... 1,500 1,873 2,113 613 240 1964 .......... 1,500 1,549 1,776 276 227 186 200 237 214 224 1965 ....... 1,474 1,502 1,594 120 92 555 566 559 613 614 1966 .......... 1,541 1,632 1,720 179 88 1967 ........ 1,459 1,517 1,566 107 49 162 171 170 170 155 1968 .......... 1,488 1,541 1,563 75 22 1969 .......... 1,491 1,545 1,551 59 6 903 937 966 9'J7 9'J3 1970 .......... 1,476 1,528 1,566 90 38 Total....... Nevada Pumping from Lake Mead ................. 25 27 31 34 41 Grand Total 5,743 5,875 5,759 5,877 5,870 The Bureau of Reclamation releases water from storage at Hoover Dam to satisfy re- quirements for the Mexican Water treaty and for the Colorado River contractors. One of the major operating problems is to meet all water demands with minimum waste. Most of the Colorado River contractors are served by diversions at Imperial Dam, The nearest major regulating structure to Imperial Dam is Parker Dam, located 148 miles upstream and three days' flow time from Imperial Dam. The ordered flow at Imperial Dam is seldom the precise rate actually required be- cause of changes in the weather and other factors during the travel time from Parker Dam. Senator Wash Dam, completed in 1966 on a tributary upstream from Imperial Dam, provides for a limited amount of additional storage which is used to balance river flows with demands. 14 . "I"he waler year lolal of scheduled deli\"eries IS not nece"~saril}' the 1,500,000 acre-foot calendar year ubligatiun under the Mexican Water Tr~'y" Plate 6 shows deliveries to Mexico during 1969-70. The extremely tight river control in recent years can be seen by comparing the total excess deliveries to Mexico with the control schedule, as shown in Table 4. The reductions in excess deliveries to Mex- ico are attributed to improved river opera- tion by the Bureau of Reclamation, to the additional regulation afforded by Senator Wash Reservoir, and cooperation on the part of the water users by more stringent water scheduling. Table 5 shows the Bureau of Rec- lamation summary of records of deliveries below Parker Dam for 1969-70. Of the 198,- 818 acre-feet of water ordered but not taken, 114,873 acre-feet was delivered to storage, 49,- 971 acre-feet was accepted by other users, and 33,974 acre-feet of the rejected water was delivered to Mexico in excess of Treaty re- quirements. California users ordered but did not take about 2 percent of the total request- ed diversions. The comparable figure for Ari- zona users was about 7 percent.