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Show be responsible for losses of 6 feet of water per acre annually and the invading mesquite and juniper for a much lesser amount, perhaps 8 inches, but significant because of the tremendous area they could invade. Other lesser plants are invading the open range. Actually, little is known as to the amount of water thus lost, but the total may be enormous. For example, the annual water loss in the upper Gila has been estimated at 100,000 acre- feet.34 The Phoenix area of the Salt River Project is said to be deprived of as much as 350,000 acre- feet of water annually by reason of the salt cedar on sediment deposits of channels and in the reservoirs during the dry season.86 One of the means by which information on the disposition of rainfall may be obtained is from the soil. Soil moisture measurements should be made at perhaps 100 places in the basin to obtain infor- mation on the movement of soil moisture through- out the year. These measurements should sample both the range of the root zone and depths below it. Associated with such measurements should be infiltration data for the wide variety of soils and cover conditions characteristic of the basin. Ground water.-Ground water information is spotty. In part, this is due as much to local apathy as to the value of information on the ground water resource. Areas of ground water in the lower basin have been determined and some information on their safe yield has been obtained. In the upper basin, ground water areas are not as well defined, are smaller, and are imperfectly known. Only a small amount of the needed information on ground waters is available. Except in local areas, only limited information is available on recharge areas. Very little is known of the boundaries, barriers, depth, and capacity of ground water aquifers in which it is possible to store ground water. Surveys of the underground reservoir in the central Arizona area have been undertaken by the United States Geological Survey. Such surveys need to be ex- tended to obtain complete data on the possibilities of the entire basin. Water quality.-Water quality is an important factor because of large amounts of salts in both surface flows and in underground basins. For ex- ample, some wells have yielded only salt water; others have had such high concentrations of salt ** National Resources Planning Board, Survey of the Upper Gila River, 1941. 38 Proceedings, Federal Inter-Agency Sedimentation Conference, Salt Lake City, 1950. as to be almost useless. The proposed export of high quality water from headwater areas (e. g., Colorado-Big Thompson, Green River) may result in higher concentration of salts in the lower basin. The wide distribution of injurious salts in the soils of the basin makes the problem most serious. At present, only about a fourth of the needed observa- tions are taken, and these are not sufficiently dis- tributed throughout the area to furnish reliable in- dications of water quality or of the expected changes. This is especially true in view of the new industrial developments, as for pulp, potash, and coal. The increasing mineralization of ground water and pos- sible means of abatement should be investigated in several parts of the lower basin. One element of water quality deserves special mention; this is in respect to mining. Throughout the mountain area of Colorado particularly, numer- ous mines are operating. Some are discharging wastes of various sorts directly into streams. Among the more poisonous are those associated with the cyanide process of gold recovery and the proc- essing of vanadium and uranium. Although efforts are made to prevent contamination with surface supplies, it is known that leakages do take place with lethal effects on fish life. Information on water quality as affected by mining is therefore needed. Sanitary water quality data are also generally inadequate in the basin. This is especially impor- tant in the mountain recreation areas. Here many small communities, dude ranchers, and campers often are not careful of their water supplies, and polluted conditions are suspected on many reaches of the streams. A system of sanitary water quality stations is needed. Sediments and soils.-Perhaps the greatest need in the basin is adequate information on sediment. Sampling has been maintained for a number of years in Utah at three stations: on the Colorado at Cisco; on the Green River near Green River; and on the San Juan River near Bluff. Key sta- tions are maintained on the lower river at Lees Ferry, Grand Canyon, and Yuma. No stations are in the Paria or Bill Williams Basins, nor on the San Rafael or Escalante Rivers. Because of the great load carried by the main river into Lake Mead, knowledge of the sediment load is imperative to proper planning of developments in the middle por- tion of the basin. It is also badly needed for some of the smaller tributary areas. The source of much of this sediment is unknown. 415 |