Scientific Investigations Report 2006–5205
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006–5205
Comparing the quantity of appropriated water and the estimated pumpage delineates existing and potential pumpage in the basin. Future planning for water supply is dependent on both quantities. The comparisons, which are for the values for 2000, also provide valuable and needed information for ground-water flow models being constructed as part of this study. Of the eight pumpage categories, estimates for six categories can be compared to the appropriated quantities. These categories are: PWS, irrigation, frost protection, livestock, commercial and industrial, and fish and wildlife propagation. Within the PWS category, two classes can be compared—the municipal pumpage and the remaining Group A and B systems. Part of the domestic class of pumpage also can be compared, but only for the 63 domestic wells with rights with a principal purpose of supplying drinking water. Pumpage for all other domestic wells with additional PRUs are included in other categories. Allowable quantities associated with these latter rights vary widely, from 1 to 2,600 acre-ft, and the estimated domestic pumpage part of the rights with additional PRUs is about 322 acre-ft; this pumpage is primarily included in the irrigation or livestock use categories. Although exempt wells do not have an appropriated quantity, a well has a legal right to pump up to 5,000 gal/d (about 5.6 acre-ft/y) and thus it also is important to account for this allowable quantity.
As of 2000, the estimated and appropriated pumpage for municipal uses was about 37,273 and 107,958 acre-ft, respectively (table 11). The non-municipal Group A and B systems have an estimated pumpage of 9,112 acre-ft compared to an appropriated value of 21,945 acre-ft. Domestic pumpage was estimated to be about 31 acre-ft for the 63 rights with a single PRU of DS and the total appropriated value was 166 acre-ft.
Irrigation accounts for the largest part of the pumpage in the Yakima River Basin and the total appropriated water for this category is 371,189 acre-ft. Estimated pumpage (271,042 acre-ft) is about 73 percent of the appropriated value and is 100,147 acre-ft less than the appropriated value. In 2000, the amount of unused appropriated irrigation water was similar to the total estimated pumpage for all other categories combined.
Pumpage associated with primary irrigation rights was about 70 percent of the appropriated quantity (266,502 acre-ft, table 11). Standby/reserve rights are associated with 104,687 acre-ft of appropriated water. Note that for any individual right, a change in a crop type can change the percentage of the appropriated value used in a year.
Frost protection pumpage was estimated to be zero and the 21 rights with a single PRU of FP (most in irrigation district boundaries and estimated to be standby/reserve) have an appropriated value of 299 acre-ft (table 11).
The livestock category includes 6,726 acre-ft of appropriated water and the estimates were set to the appropriated quantity (table 11), so there is no difference between the two values. Livestock uses associated with irrigation-rights category average about 25 percent of the appropriated value and were estimated to account for about 5,166 acre-ft of the irrigation total. Compared to the livestock category, there is a large difference between the estimated and appropriated quantities of pumpage for the commercial and industrial category. Estimated pumpage, 7,230 acre-ft, was only 23 percent of the appropriated quantity (table 11) resulting in a difference of 24,389 acre-ft. The difference between estimated and appropriated values also is large for the fish and wildlife propagation category, but the estimated pumpage in table 11 does not include about 4,500 acre-ft of pumpage for wells without appropriated quantities.
Estimated pumpage in 2000 from all wells with rights was about 60 percent of the appropriated quantity, representing an absolute difference of 220,164 acre-ft. This quantity is reduced to 198,289 acre-ft (about 275 ft3/s) when standby/reserve pumpage is not included (about 60 percent of the appropriated quantity). Thus, as of 2000, the total unused part of the appropriated annual quantity is larger than the estimated pumpage for most categories and is about 56 percent of the total estimated pumpage in 2000. To understand potential effects of new pumpage on the ground-water flow systems, it will be important to estimate the potential effects on ground-water availability if all appropriated water were withdrawn.
Based on the estimated number of exempt wells in the basin as of 2000 and using the maximum allowable withdrawal rate of 5.6 acre-ft, an estimate was made of the allowable withdrawals from exempt wells. This quantity was about 241,000 acre-ft or about 215 Mgal/d in 2000. This quantity is larger than the estimated primary irrigation pumpage in 2000. The potential effects of all exempt wells withdrawing the full allowable amount also need to be understood.
U.S.
Department of the Interior | U.S. Geological
Survey
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