15. El Jardin and Salineno storage reservoirs.-The Mariscal Reservoir will provide regulation, flood control, and hold-over storage for the Lower Rio Grande but there is still need of storage nearer the irrigable areas beginning at Rio Grande City and extending to Brownsville. Storage possibilities have been investigated by a board of engineers representing the United States and Mexico but the Mexican section stated that studies should be postponed until an agreement had been reached in the matter of equitable use of water. Several sites, however, were investigated by the American engineers and the surface indications point to favorable locations at El Jardin at the northwest corner of Webb County where a dam 70 feet above low water and a crest length of 3,470 feet would provide storage for 200,000 acre-feet and a second site farther downstream near Salineno, in Starr County, where a dam 45 feet above low water and a crest length of 2,160 feet would create a reservoir with a capacity of 100,000 acre-feet. Further studies will have to be made to determine the foundations at these sites and also the desirable capacities of the reservoirs. 16. Alamogordo Reservoir.-Irrigation is the principal use of waters in the Pecos Valley. The Government has constructed the Carlsbad project, with an area of 25,000 acres of irrigable land which is now confronted with periodical shortages of water. This difficulty can be eliminated in part by lining the principal canals with concrete at an estimated cost of $250,000, and further by the construction of the Alamogordo Reservoir, with a capacity of about 70,000 acre-feet, located near the town of Fort Sumner, about 150 miles above the Carlsbad project. The estimated cost of the dam and reservoir is about $2,000,000. 17. Red Bluff Reservoir.-For the conservation and utilization of water in the Pecos Valley below the Carlsbad project, storage reservoirs are needed. Plans have already been initiated for the construction of the Red Bluff Reservoir, a short distance south of the New Mexico-Texas State line. The Public Works Administration has made a loan and grant of $2,600,000 to the Red Bluff Water Control District of Pecos, Tex., for the construction of an earth dam, with power house and transmission line to be used for irrigation and power development. 18. Soil erosion has become a serious problem in the upper and middle Rio Grande Valley. Reservoirs that have been constructed are being filled with silt at a rapid rate, and unless effective means are taken to prevent continued erosion, the capacity of Elephant Butte Reservoir will be reduced to such an extent that within a relatively short time the Rio Grande project, embracing an irrigable area of 155,000 acres, will be confronted with an inadequate supply of water. The principal item in the erosion problem is overgrazing on public, private, and Indian lands throughout New Mexico, starting with the influx of settlers from other States, beginning with the cession of this area to the United States in 1848. 19. Six major water-supply systems of the basin, located in Texas and New Mexico, serve about 206,000 people. Of the population thus served, domestic supplies for about 66,000 people are taken from surface sources, while about 140,000 persons use ground-water supplies. Surface water supplies throughout the basin are notably deficient and in view of this fact, ground water assumes great im portance. 20. In San Luis Valley, Colo., on the headwaters of the river, the water table generally is close to the surface, and large quantities of ground water can be developed by means of drains or wells or both, thereby benefiting the lands of the valley and providing additional water for irrigation or domestic use in areas downstream. There is some irrigation from wells in the middle stretch of the river around Las Cruces, N.Mex., and El Paso, Tex., and in the Lower Rio Grande Valley in the vicinities of McAllister and Mission. In these areas the prospects are promising for additional ground-water development of considerable magnitude for the irrigation of selected lands having good natural drainage. Adjacent to the lower Rio Grande Valley in south Texas, and essentially a part of the valley, although located in the basin of Nueces River, is an area commonly known as the "winter garden district" in which about 30,000 acres are irrigated from wells for the production of valuable crops of winter vegetables. In some parts of this district ground-water development can be expanded to some extent and in others it has reached the limit of safety under present conditions, but in these localities the possibilities are believed to be good for replenishing the ground-water reservoirs by spreading flood and waste stream water on the outcrop of the Carrizo sandstone, the chief water bearing formation. In the Pecos Valley approximately 45,000 acres in the vicinity of Roswell, N.Mex., and 2,000 acres in the vicinity of Pecos, Tex., are irrigated from wells and approximately 16,000 acres in the vicinities of Balmorhea and Fort Stockton, Tex., are irrigated from large springs. 21. The fact should be emphasized that any large-scale program of intensive development in the Rio Grande Basin will properly require basic stream-flow and ground-water data to supplement the information now available. The estimated cost of such river-measurement work is $210,000, and of ground-water investigations, $100,000. The latter figure includes the cost of ground-water work in the Pecos Basin and in closely adjacent areas in the basin of Nueces River. 22. A comprehensive plan for the utilization of the water resources of the Rio Grande will provide primarily for irrigation, flood control, and watershed management. The latter feature, including forestry, range-land management, and special measures for erosion control, is considered in the supplemental material attached. SUPPLEMENTAL STATEMENTS OF THE DEPARTMENT OF THE INTERIOR UTILIZATION AND REGULATION OF UNDERGROUND RESERVOIRS (Submitted by C. G. Paulsen, Geological Survey, Department of the Interior) The drainage basins of the Gulf region contain natural underground reservoirs that have very large storage capacity. These reservoirs are of three kinds: Deposits of alluvial gravel, Coastal Plain deposits of unconsolidated or partly consolidated sand of both land and marine origin, and cavernous or honeycombed limestone and marl. The alluvial deposits are the chief water bearers in the immediate valley of the Rio Grande, the Coastal Plain deposits form great reservoirs in a belt bordering the Gulf from the Rio Grande to Florida and the limestones and marls provide the principal underground storage in the Pecos Valley in New Mexico and West Texas, in the upper part of the Coastal Plain in Texas, Louisiana, and Mississippi, and in Florida. The underground reservoirs are already extensively utilized. In the area covered by Texas, Louisiana, Mississippi, Alabama, Georgia, and Florida, about 80 percent of the total population obtains water supplies from wells and considerably more than half the water furnished by public supplies is derived from wells. Houston, San Antonio, Galveston, and El Paso, for example, derive their water supplies entirely from wells. Wells tapping the underground reservoirs are also extensively used for irrigation. According to the census reports there were in 1929 about 3,300 wells producing irrigation supplies in the coastal plain of Louisiana and Texas. These wells had a total capacity of about 3,700,000,000 gallons a day or about 6,000 cubic feet per second. According to an investigation by the United States Geological Survey described in Water-Supply Paper 639 "Geology and ground-water resources of the Roswell Artesian Basin, New Mexico", wells producing water for irrigation in the valley of the Pecos River in the vicinity of Roswell, N.Mex., had a total capacity of about 850 cubic feet per second in 1927 and about 45,000 acres were irrigated from them. Areas of considerable size are irrigated from springs and wells in western Texas and along the northern borders of the Coastal Plain in southwestern Texas. In some localities in this region the underground reservoirs are practically untouched, in others they are partly developed, and in a few localities the withdrawals of underground water have reached the limits of safety. In view of the large capacity of the principal underground reservoirs their value is determined largely by the quantities of water that are available for recharge and by the intake facilities. The principal water-bearing beds of the region crop out in zones ranging in width from 1 to 2 miles up to 50 miles. The beds dip generally to the east, southeast, and south, which are also the general directions in which the land surface slopes, and from the outcrop the formations extend in these directions to progressively greater depths beneath the surface. The water stored in the underground reservoirs is derived from rainfall on the outcrop area of these formations and from streams that cross their outcrops. Artificial recharge in areas of natural intake has been practiced to a considerable extent in southern California and is planned on a large scale in the San Joaquin Valley. It can be best accomplished by artificial spreading of water over areas where the permeable formations crop out. In all comprehensive plans for the higher utilization of the water resources of this region serious consideration must be given to the full utilization and regulation of underground reservoirs. This involves first a careful study of the safe yield of the underground reservoirs under natural conditions. This has been done in the valley of the Pecos in the Roswell artesian basin and in a part of the Gulf Coastal Plain in Texas. The most important results of these investigations are given in Water-Supply Paper 639 and the following mimeographed memoranda: Survey of the underground waters of Texas; February 16, 1931. Underground-water resources of Atascosa and Frio Counties, Tex.; October 13, 1932. Ground-water resources of the Houston-Galveston area, Texas; October 17, 1932. Ground-water resources in the Houston district, Texas; December 29, 1933. Ground-water resources of Duval County, Tex.; February 12, 1933. Secondly, the possibilities must be considered of adding to the natural supply by artificially inducing flood waters to percolate underground which would otherwise go to waste. Areas in which it is believed this could be done to some extent include the valleys of the Pecos, Nueces, Guadalupe, Colorado, Brazos, Trinity, Neches, and Sabine Rivers. In some of these areas this method of storage may prove to be more feasible than a system of surface reservoirs. SOIL-EROSION PROBLEMS (Submitted by Soil Erosion Service, Department of the Interior) The major economic problem on the watersheds of all of these streams pertains to necessary regulation of the rainfall for controlling the exceedingly serious problem of accelerated erosion and run-off resulting from (a) the system of excessive one-crop cultivation of sloping land along the eastern streams and (b) overgrazing of the watersheds along the western streams. Some of the most serious erosion of the country is to be found over tremendous areas within the basins of all of these streams. Available measurements of erosion and run-off are tremendously increased by the one-crop type of agriculture obtaining pretty well throughout the Cotton Belt portion of these watersheds. There is little possibility of effecting permanent flood control and no possibility whatsoever of preventing the silting of stream channels and reservoirs and the covering of fertile bottom lands with infertile products of erosion except through a vast improvement with respect to land utilization and protection. In the paragraphs below the problem of water control as relating to run-off, erosion, silting, and sedimentation of valley lands is briefly discussed. Apalachicola River.-This river, which receives the drainage from the Chattahoochee and Flint, flows for the most part through a highly erosive region, down nearly to the edge of the Gulf Flatwoods, which extends inland about 30 miles from the Gulf of Mexico. The basin of the Chattahoochee is very largely occupied with highly erosive soils. The upper half flows through the Piedmont region from north Georgia to the "fall line" at Columbus, Ga. Practically every acre of upland over this large proportion of the basin consists of erosive soil, most of it highly erosive. For example, in Hall County, Ga., alone, something over 100,000 acres have been mapped as steep eroded land, all of which was formerly cultivated and all of which is now essentially ruined by erosion. In addition, nearly 100,000 acres of cultivated land in the same county are suffering severely from erosion, with numerous fields abandoned every year. Over much of this eroding land the original absorptive topsoil of sandy loam and clay loam has been washed off down to comparatively impervious clay subsoil, and gullying, representing the beginning of the death stage of land, is setting in over fully a third of this second hundred thousand acres. This condition is approximately representative of the major part of the upper watershed of the Chattahoochee. Below the fall line at Columbus, something over 50 percent of the land within the drainage basin of the Apalachicola, down to the confluence with the Flint River, is highly erosive. In the Clay Hills section, a belt about 25 to 50 miles wide immediately south of Columbus and extending west across Alabama into Mississippi, much land has been so terrifically washed that it has been ruined and abandoned. Much of this, however, is now restocking with pine. The remainder of the uplands is scatteringly cultivated, and in every sloping field every rain heavy enough to cause water to run downhill sweeps off large amounts of soil to choke the channelways below, and to cover alluvial plains and lower slopes with infertile erosional debris. South of the Clay Hills section is a broad belt of upper Coastal Plain country, of somewhat smoother relief, though generally rolling over approximately 65 percent of its area. Erosion is very serious in many parts of this region. For example, in Stewart County, Ga., 70,000 acres of formerly cultivated land have been permanently destroyed by gullying and deep sheet washing. Here are probably the deepest gullies of the Western Hemisphere, for the development of which man is responsible. One of them, Providence Cave, is nearly 200 feet deep, although it is definitely known that a little more than 50 years ago a portion of this gully was in cultivation. Similar gullies have cut to pieces, as stated, approximately 70,000 acres of land in this one small county, and all of this material has been sent on its way toward the Gulf of Mexico via the Chattahoochee and Apalachicola. The Flint River also heads in the highly erosive Piedmont country, but the greater part of its watershed is confined to the middle Coastal Plain section. In this basin erosion is not so severe as along the Chattahoochee. Numerous areas, however, are subject to very violent washing. |