WSP11269 - Laserfiche WebLink

Home Browse Search

, i , I I i . I , ~" 1&8,) , assumption tllat actual diversions of water during the review period were equal to tile ideal diversion requirement. In our judgment, Case 1 is Il10re realistic tllan Case 2, but probably still understates the inflow to John Martin Reservoir since it is based on irrigated acrea~es that are larger than were actually irrigated. The irrigated acreage used were obtained from the Colorado Ayricul tural Stati stics whiCh i ncl ude an unknown amount of lands outside the Project. From a standpoin"c of injury to downstream users, Case 1 gives the most reasonaole results. However, none of the tnree studies gives a true pic- ture of injury because they do not compare the actual conditiun to a "without proJect" condition. We investigatea making the "without project" compari son and concl uded tllat tnere was not suffici ent in formation avaiiaule to make loeanin~ful comparisons. Tne Kansas officials have aryued the impacts of tne Project must be eva- luated on an annual basis rather on an average annual basis. This has merit as it applies to the 197!:i-d4 review period. Jonn Martin Reservoir be~an a filling cycle on November 1, 1982, culminating in a spill of John Martin Reservoir in May i~85. As shown in results for Cases 1, 2 and 3 (see Table 4), the inflow to John Martin was depleted during the period, preceding the fill cycle, out was enhanced after the beginning of the fill cycle. The depletions before the beginnin~ of tne fill cycle resulted in a loss or usable water to Kansas, whereas the enhancements occurring after tile beginning of the fill cycle were not usable because they were lost in the spill. The average annual net impact on the inflow to John Martin Reservoir for the review period up through December 31, 1982 were -2000 acre-feet, -330U acre-feet and -500u acre-feet for Cases 1, 2 and 3, respectively. The average annual i/lllacts for the entire review periOd were +600 acre-feet, -ouO acre-feet and -l!:iuu acre-reet. Tile occurrence of depletions before the beginning of the fill cycle and ennancement after were a direct result of the large reduction of irrigated acreage during the early years of the review period. During the early years when less land was irri ~ated tne excess water supply was stored in Tri nidad Reservoir. The return flows durin~ tnis periOd were reduced due to less land being irrigated. In tile years after the beginniny of the fill cycle, more 1 and was irrigated ana, because of an abundant supply, more water was app1 ied resulting 1n increast:o return flows and enhanced inflow to John i'iartin Reservoir. Tnere is no reason to expect that toese ci rcums tances wi 11 be repeated and, tllererore, shou 10 have no bear; ng on future amendments to tne operating pri n- ciples. Notwitnstanding the circumstances of 1979-d4 review period, we see no reason why the impacts 011 Jotm Martin Rest:rvoir snould not continue to be evaluated on an average annual basis. The Triniaad ProJect, by its very nature of reregulatioll, will result in reduced inflows to JOhn Martin Rest:rvoir in some years and enhancea flows in other years. Table 25 of the 1 !161 Sway shows annual enl1ancement of as IIl.Icil as 8,UOO acre-feet and an annual depletion of as much as lU,uuu acre-feet. The 1961 Study also shows tnat enrlancements to inflow to John t~artin Reservoir generally occurred in dry years and depletions occurred in wet years. As illustrated in Table 7 (from Table 25 of the bl61 Swdy), the Project when compared to historic operation would increase the inflow to John Martin Reservoir in 16 of the 21 driest years and WOUld decrease the inf"low in 8 of the 12 ~Iettest years. The largest depletions (Rev. 12/27/88) 26 -