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<br />00.2891 <br /> <br />(JVW rt't~P~ ~ <br />(p~~~~~ J~ <br />a.S?~.D~~~f1>~ <br />(C (o{O~;e. CP tJf( ("o~~ <br /> <br />Upper Basin Hydrology Data Base. ~~{e.~"o~~ <br /> <br />The natural inflow hydrology data base (CRSS) introduces an <br />average 227,000 acre-feet (af) of additional runoff above Lake Powell, as <br />compared with the modified, depleted inflow data base employed by CRSP, <br /> <br />. <br /> <br />a. <br /> <br />The CRSP model's inflow data were intended to portray historical <br />flows reduced to those that would have occurred, given the 1968 level of <br />depletion. In order to compare the two data sets, we adjust the CRSP data <br />to reflect the' undepleted condition. This is done by adding the depletions <br />which occurred in 1968, which were estimated to be 2,771,000 af. The <br />227,000 af difference between the two estimates of undepleted Upper Basin <br />runoff is only about 1.5 percent of the annual natural runoff at <br />Lees Ferry. <br /> <br />The depleted runoff data base used with CRSP was first compiled <br />in 1969 for use in studies performed in conjunction with the development of <br />the 1970 operating criteria. Additional years were customarily added to <br />the data set as the preceding year's records became available. Adjustments <br />were made so that the additional inflow data continued to represent the <br />1968 level of depletion. <br /> <br />The data and procedures used in the development of the natural <br />runoff data base are documented. The natural flows are the result of a <br />more rigorous and exact procedure than the modified depleted inflow data. <br />Also, the fact that they are documented lends them usefulness and <br />credibility. Future updates to the data base can be expected to be <br />procedurally consistent with the existing data base. It is doubtful that <br />any similar documentation of the modified depleted inflows will be <br />produced. <br /> <br />J b. Shortages to Scheduled Demands in the Upper Basin. <br /> <br />In CRSS, certain water'demands, primarily in the headwaters of <br />the Upper Basin of the Colorado River, are not met because there is <br />insufficient water at these specific sites in the river. This reduces the <br />total water depletion in the basin below what was scheduled to occur. <br /> <br />CRSP, by comparison, did <br />specific manner. All demands were <br />available upstream of a reservoir. <br />Upper Basin scheduled demands were <br /> <br />not treat demands in the same site <br />met from the aggregate water supply <br />In this way, virtually 100 percent of <br />satisfied. <br /> <br />The difference in these two models' treatment of scheduled <br />demands amounts to about 200,000 af per year. Almost all water not <br />depleted will become inflow to Lake Powell, thus the difference translates <br />almost directly to a 200,000 af per year difference in inflow to <br />Lake Powell. <br /> <br />c. Significant Differences in Lower Basin Reach Inflow. <br /> <br />The CRSP model did not use an inflow data base below Hoover Dam. <br />Instead, a historical average amount of water loss (or gain) was introduced <br />into Lake Mohave and Lake Havasu operations. Scheduled releases from <br /> <br />2 <br />