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<br />002553 <br /> <br />Although various Indian tribes had been irrigating lands along <br />rivers and streams in Arizona for many centuries, the first white <br />settlers began diversions in the mid-1800's. Throughout the remain- <br />der of the century, canals were extended and new canals built that <br />increased the irrigated acreage. In the 1890's, alternating severe <br />flood and drouth conditions beset the Salt River Valley. The <br />tenacity and determination of the people resulted in the formation <br />of an organization pledged to rebuilding its agricultural enterprise. <br /> <br />Following enactment of the Reclamation Act of 1902, Arizona, <br />still a territory, immediately moved forward. Construction of <br />Theodore Roosevelt Dam in the Salt River Canyon was started in <br />1905 and was completed in 1911 by the Bureau of Reclamation. <br /> <br />In 1917 the Salt River Valley Water Users' Association <br />assumed responsibility from the Bureau of Reclamation for the <br />operation and maintenance of the Salt River Project, The Associa- <br />tion also undertook the responsibility of distributing the Project's <br />water and power supply. Between 1922 and 1930 the Salt River <br />Project constructed three additional dams in the Salt River Canyon <br />with funds obtained by separate bond issues. These dams, with <br />power-generating facilities included, increased the electrical <br />supply to the valley for pumping from the vast underground water <br />supply. <br /> <br />Bartlett Dam on the Verde River was constructed in the period <br />1935 to 1939 by the Bureau of Reclamation, and Horseshoe Dam was <br />constructed from 1944 to 1946. <br /> <br />The flow of the Gila River was also inclined to flood and <br />drouth cycles and could not be depended upon to provide a firm <br />water supply during summer irrigation periods. In 1929 the Bureau <br />of Indian Affairs started construction of Coolidge Dam on the Gila <br />River to store and regulate the riverflows for beneficial use of <br />the Gila River Indian Reservation and non-Indian lands in the San <br />Carlos Irrigation and Drainage District. The relative righLs <br />between upstream and downstream water users were settled in 1935 <br />upon the entry of the Gila River Decree. <br /> <br />In the Salt and Gila Valleys of central Arizona, ground-water <br />development has continued since early days. The advent of the <br />turbine pump and the production of inexpensive electrical energy <br />made deep-well pumping feasible. Many thousands of additional <br />acres of land have been developed in the past several decades which <br />depend upon ground water alone. The net result has been a steady <br />decline in the ground-water table throughout central Arizona, as <br />the ground-water reservoirs are being depleted year by year. This <br />accelerated decline in water levels has, in turn, resulted in land <br />subsidence. <br /> <br />11-4 <br />