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., . . . . . -":2.. - He found tha~'the net regulation capabili~y of ~he exis~in~ (1959) sys~em of Colorado River reservoirs would be raised ~o 5,800,000 acre-fee~ per year if Lake Powell were filled to its capacity (at a level of 3700 feet)* and 5,720,000 acre-feet per year if storage were limited to a 360Q-foot elevation. Of the total 80,000 acre- feet which wouLd be b::lst each year. about one-half would be chargeable to the state of Colorado. This f~re. 40.000 acre-feet per year, is only five percent of the amount quoted by' the state in its le![al. ar!,=ents. The reason for this almost infinitesimal increase in water regulation with in- creasing storage, capacity is a combination of two factors: (a) the Colorado River Basin has such a gre~ amount of reservoir space at present that it is almost totally regulated. and (b) iDcreased evaporation from the F!Y'eater surface area resulting from the higher wat~ level would wipe out almost all of the increase in reF!ulation capa- bility. At 3700 feet. the area of Lake Powell would be 161,390 acres as opposed to only 98.470 acres' at 3600 feet. This increased acreage would lead to increased evap- oration losses of'marl!! than 300.000 acre-feet per year. Another factor 8hich ~as not coverea by Langbein is the effect of increased seep- age losses due to raising the level of the reservoir. About one-fourth of the water flowing into the, reservoir today is lost in this !:'.anner.4 I;hile this rate is likely to decrease somewhat as the surrouncing aquifers beco~e saturated, it will not level off for many decades. Even when it does. a si~ificant ~.ount of water will still find its way back in~ the river below the dan without flowing through the power tur- bines or the gaging station.*~ Increasing the w~ter level from 3600 to 3700 feet wo~d cause an increase in seeoage losses of 10 to 15%, deoending on the permeability of the rock located between the~e two elevations. While th~ amcunt or additional water lost by this method cannot be calculated exactly, it would undoubtedly be greater than the 80,000 acre-feet per year of ~tion capability to be gained by raising the water level. Thus the filling of Lake Powell would not only ~educe the ability of the uoper basin states to fulfill their Obligations to deliver water to the lower basin, but it would also reduce the amount of ~ater available for use in the uooer basin by at least 300,000 acre-feet. per year. more than 5% of the upper basin's total supply. (2) The state vould lose $l70.000.000 in power revenue. IvaI Goslin, executive director of the Unoer Colorado River Commission, has used a much lower figure of $2.300,000 per ue~~ fer the upner basin as a whole.5 This figure is based on the 100- foot difference in prESsure head occasioned_by a lower water level. But po~er produc- tion also deoends on the amount of water flowing throu~h the turbines. Since more than 300.000 acre:feet, of ~ater ner year would become unavailable for oow~r p~od~ction if the reservoir wer~ fLlled. the quoted revenue loss should be reduced proportionally.*** The average vaLue of the water delivered by the Colorado River Storage Proiect is approximately $35 per acre-foot.6 Assuming that the same value applies as well to the remaining water in '!:be river, the value of the water to be lost by the upper basin states by filling'Lake Powell would be more than $10,000,000 per year, several times the amount to be gained by producing more power. filling the reservoir would then re- sult in a net financial Loss to the upper basin which is much larger than the amount 'claimed as a p:ain'.. o *It is interes~g to note that. according tc Lan~bein, any increase in storage capa- city above that now in existence would result in no further increase in regulation capability. **One "victory" claiD!d by the proponents of fiUinf' Lake Powell is the support of the lower basin states' faro th is action. This support is quite natural. Higher watel' levels would result in p,reater seepage around the dam. This water would be a bonus to t~e low- er basin. since it does not return to the river until it is below the measuring poin~ separating the two basins. Therefore it is charged to the uppe~ basin states, but bene- fits only the lower. ' ***Water available far paaer nroduction at Hoover ran and others would also be reduced. but this does not ~ffect the Up~r Basin States.