WSP00282 - Laserfiche WebLink

Home Browse Search

o w .\.) o HISTORY OF DEVELOIMENT the irrigated acreage, but Some lands J.o not receive a full supply. No accurate determination can be made of the actual amount of water con- sumed because not all of the diverted water and practically none of the return flow is measured. The consumptive use is estimated by the appli- cation of appropriate consumptive use rates to the irrigated acreage. As water exported from the Upper Basin during the same period aver- ages about 315,000 acre-feet, the estimated average Upper Basin consump- tive use was about 2 million acre-feet per year. Since completion of the Colorado-Big Thompson project with initial diversions made in year 1947, the transmountain diversions have increased to around 500,000 acre- feet. Yearly increases or decreaseS in reservoir content affect annual depletions from the Colorado River, but these changes have l:ittle effect on average depletions. Essentially all surface water available for use in the Lower Basin is now appropriated. The additional development of lands for irrigation in new areas necessarily will be limited to small areas on tributaries to be supplied by the conservation of flood waters; the development of ground water; adjustments in present water uses; and the salvage, where feaSible, of present losses. C. Water Comp1:lct and Treaties L Colorado River Compact Water of the Colorado River was divided between the upper and Lower Colorado River Basins by the Colorado River Compact which was signed in 1922 by a connnissioner of each of the seven States of the river basin and by a representative of the United states. All states but Arizona rati- fied the compact prior to its effective date in 1929. The dividing point on the river between the Upper and Lower Basins is at Lee Ferry which is defined as a point one mile below the mouth of the Paria River. The com- pact apportions to each of the Upper and Lower Basins in perpetuity for exclusive beneficial use a total of 7,500,000 acre-feet anllilltlly. In ad- dition to the apportionment of 7,500,000 acre-feet, the Lower Basin is given the right to increase its beneficial consumptive use of water from the Colorado River system by 1,000,000 acre-feet annually. The compact further provides that the states of the upper division will not cause the flow of the river at Lee Ferry to be depleted below an aggregate of 75 million acre-feet for any period of ten consecutive years. One provision in the compact permits exportation of the water out of the basin as long as it is used beneficially in the seven basin states and another provision recognizes the obligations of the United states to the Indian tribes. The compact prescribes the manner in which the waters of the Colorado River system may be made available to Mexico under any water rights recognized by the United states. 11