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Show Sufficient funds and personnel should be provided to enforce the acreage limitation. In general, the volume of land transfers is large and much work is required to check land transfer records and legal aspects to insure compliance. 3. Problems Associated with Overdrafts of Ground Water The Problem Current difficulties created by overdrafts from ground water basins. The Situation During the last 30 years pumping of ground water has become important as a means of supplementing surface water supplies in old projects, of supplying new land areas, and of draining lands which de- veloped a high water table under irrigation. Sur- face flows must be used as they occur or be lost to the individual irrigator; ground water is reservoired water, available upon demand, and as such is sub- ject to abuse. An area of about 670,000 acres in the Salt and Gila River Basins of south central Arizona ** is taken as an example. Irrigation here started from a sim- ple diversion structure in a flowing stream. In time, the area dependent upon that simple system became commensurate with the flow of the stream during periods of favorable runoff; in drought periods some lands suffered shortages. So the first manifestation of the need for measures to offset overdevelopment of land dependent upon water took the form of a demand for a surface reservoir. Roosevelt Reservoir on the Salt River was the result. With continued irrigation and no artificial drain- age, the water table rose and relief was obtained by pumping. It soon became recognized that pump- ing produced water of good quality surplus to the needs of the project area, so this water was turned over to good lands adjacent to the project. Irriga- tion from ground water was found to be profitable, and expansion followed from 1915 and 1916 on- ward. Around the lands depending on ground water, communities were established with the usual facilities such as roads, schools, churches, utilities, and stores. Ground water in this area, as elsewhere, was ex- haustible. Withdrawals from the underground MFrom San Carlos and Roosevelt Reservoirs down- stream. basin commenced to exceed average recharge, and for some time have been at the expense of gradual exhaustion of the underground reservoir. This first became generally apparent in the late 1930's and early 1940's. The Bureau of Reclamation esti- mates that of an average of 1,163,000 acre-feet an- nually pumped from the ground water during the period 1940-44 in this area, 468,000 acre-feet rep- resented an overdraft. The water level in wells on the perimeter of the area has declined by 200 to 300 feet since the beginning of pumpings. Wells now reach depths of 2,000 feet below the surface. In addition, the use and reuse of water for irrigation results in an accumulation of harmful salts in the water unless the salts are carried away by water re- leased from the area of use. To maintain a salt balance in the area, 154,000 acre-feet should be re- leased, considerably more than now flows out of the area. The irrigation enterprise in the area could be made commensurate with its water supply only at the expense of reducing production on the 670,000 acres about one-third. The first pumper had no reason to expect an ulti- mate shortage of ground water. Until the last 5 to 7 years, very few admonitions reached individuals planning the sinking of a well. Even during the years of awareness since 1940, the profits to be made out of a short-lived ground water development have been such as to eliminate caution. The end result of the dissipation of the ground water resources will be abandonment of a consider- able part of the agricultural economy, with the dis- tress and business failures which accompany such abandonment. How does an agricultural economy precariously based upon overdraft of ground water come into being? Overdraft of ground water in the basin most frequently has been the result of inadequate in- formation upon which to base reliable estimates of safe yield. Unlike surface reservoirs, the under- ground reservoir is not visible; the newspapers do not publish its status; and in all basin States the underground reservoir is everyone's property, no individual's responsibility. Whatever the govern- mental responsibility to advise and protect indi- viduals who propose to engage in a ground water irrigation enterprise, in most areas Government agencies have not been and are not yet prepared to give advice. This is without known exception in the basin. However, protection to those enterprises which have a firm water supply may be accom- plished under measures of State control. 911610-51- -27 395 |