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. Altogether, 67 percent of the watershed consists of land which, under cultivation, is subject to severely impoverishing erosion. Less than one-fifth of the watershed of the cultivated portion of the Apalachicola is devoted to soil-saving crops. Farming is extensively practiced throughout the entire watershed, except in the very flat country near the Gulf. Control. Any far-reaching effective control must follow along the lines of procedure given above for the Savannah-Santee watersheds. Alabama-Coosa system.-With the exception of a very narrow strip along the Gulf, this entire system flows through one of the most erosive sections of the Gulf region. Of the entire watershed, 77 percent consists of land of highly erosive character. From the very head of the Coosa in the Blue Ridge Mountain region of northwest Georgia, on down through the limestone and shale valleys, across the southern extension of the Piedmont, and finally through the hilly upper Coastal Plain, the Black Prairies and Clay Hills sectors, soil washing is going on in nearly every field except those situated on the flat stream bottoms and the occasional flat-floored interridge valleys. In many places the stream bottoms have been buried with a foot to several feet of erosional material washed out of the hills. In the Piedmont, the original uniformly textured dark-colored soils of the creek bottoms have been buried with reddish varitextured, poor subsoil material and light-colored sand washed out of the uplands, over approximately 75 percent of these alluvial plains. In the Black Prairies the topsoil has been removed down to yellow clay over every sloping area; and, unfortunately, most of the region is of sloping topography. This area, formerly representing a highly developed agricultural unit, has become relatively decadent because of the ravages of uncontrolled erosion. Only 8 percent of the crops grown in this region belong in the category of soil-saving plants. Erosion is so widely spread under the prevailing one-crop system of agriculture that it would be utterly hopeless to make anything approximating the most beneficial use of the regional waters without carrying through erosion-control measures over approximately half of the entire watershed. The areas that will not need treatment are represented largely by lands covered with second-growth pine and the flat nonerosive lands of the Coastal Plain, valley floors, and flat-topped ridges. The Alabama-Coosa watershed stands at the top of the streams of the eastern Gulf region, if not of the entire Gulf region, with respect to the seriousness of the problem of uncontrolled surface waters. Control. There is no other possible practical way for utilizing the run-off waters of this river system in a really resourceful way except through control of erosion. Any existing reservoirs or any reservoirs that may be built certainly will be rapidly filled by sedimentation unless the ravages of uncontrolled rainwater are curbed. The details of procedure for any such control must conform to a well-rounded, coordinated program of reorganized land-use practice, including an enormous amount of erosion-control work. The plan of the Soil Erosion Service, as briefly outlined under the discussion of the Savannah and Santee watersheds, obviously is the only possible way by which any real progress in this direction will ever be made. All other attempts thus far have been characterized to a large degree by failure. Tombigbee-Warrior system.-Erosion on the watershed of this system is generally bad, it does not average quite so bad as over the watersheds of the Alabama-Coosa and the Apalachicola systems. It so happens that a very considerable part of the watershed lies within a region of predominantly clay soils, principally the Black Prairies and Clay Hills sections of western Alabama and east-central Mississippi. Most of these soils are highly erosive and great areas have been abandoned because of their depletion by rainwash. Much of the eroded matter, however, is carried in the form of very fine textured material. This passes into the Gulf of Mexico, probably to a considerably larger extent than the more sandy coarser-grained suspension of the rivers to the east. Predominantly, the basin carrying this drainage system is highly erosive, 70 percent according to surveys thus far made. Much land has been worn out and abandoned and grown up either in old field pine or stands of volunteer vegetation that have effected fairly good control over scattered areas. Still the problem of erosion is so extensive and serious that much work must be done to provide better control of the run-off, otherwise land wastage by erosion and overwash will continue, and ruinous silting of stream channels and reservoirs cannot be avoided as difficult problems of river management. The proportion of the extensive area of cultivated land used for the soil-saving crops amounts to 12 percent of the total cultivated area. Pearl River. This river flows principally through the region of loess soils and the moderately rolling upper Coastal Plain. The region of loessial soils above Crystal Springs, Miss., is very largely highly erosive, while scattered areas throughout the predominantly sandy Coastal Plain country through which the lower half of the river flows are also very erosive and contribute much sandy material to the flood waters finding their way into the Pearl River. In recent years there has been some tendency for the farmers of some localities, as in Hinds County, Miss., to grow more grass and lespedeza. Regardless of such worthy efforts, however, only 8.5 percent of all the cultivated land was devoted to the soil-saving crops, according to the last census. About 50 percent of the total watershed area is subject to serious erosion, but the proportion is much greater in the northern extension, especially on cultivated land. The remainder consists largely of flatwoods and timbered or cut-over areas. On the whole, the erosion problem is somewhat less serious in the Pearl River Basin than in the basins of the Apalachicola, Alabama, or Tombigbee. Control would be along the same lines suggested for the rivers to the east. Sabine-Neches system. About half (48.5 percent) the watershed of this system consists of highly erosive land. There is comparatively little erosion in the broad belt of coastal prairies skirting the Gulf of Mexico, and not a great deal in the next higher and somewhat more rolling belt of the interior flatwoods. The upper half of the watersheds, however, is very largely rolling country and all of the upland is erosive where used for the clean-tilled crops. Cotton so largely predominates that the agriculture can be characterized as strictly of the erosion-producing type. The most extensive soil in this upper section is the Kirvin fine sandy loam. Under continuous cotton production on about the average slope (7.8 percent), the annual loss |