Geology topics
Publications and source records attributed to J.G. Cronin.
The Brazos River Basin in Texas extends from the New Mexico State line southeastward to the Gulf of Mexico. The basin is about 600 miles long and ranges in width from 1 to 120 miles--an area of about 42,000 square miles, which includes all or parts of 69 counties. About 1,385,000 persons reside in the basin.
The Ogallala Formation of Tertiary (Pliocene) age is the principal aquifer in the Southern High Plains of western Texas and eastern New Mexico. This heavily pumped aquifer supplies practically all the water used for irrigation, municipal, industrial (except oil-field repressuring), and domestic purposes. Although the ground water in the Ogallala Formation in the Southern High Plains is common to both Texas and New Mexico, the State laws concerning ownership of the water are different. The New Mexico statutes provide that all underground waters of the State belong to the public and are subject to appropriation for beneficial use (Reynolds, 1961, p. 79). Under conditions specified in the law, the State Engineer may declare certain areas as underground water basins in which the State Engineer has jurisdiction over the drilling of wells. The approximate boundaries of two such basins in New Mexico are shown on the maps. In Texas, the landowner owns the underground water. Under a law passed by the Texas State Legislature in 1949, underground water conservation districts may be formed with the authority to make rules and regulations for the conservation of ground waters, such as rules governing the minimum spacing of wells, and rules for the prevention of waste and contamination of fresh water, and other practices for the conservation of ground water. The approximate boundaries of two underground water conservation districts in Texas are shown on the maps.
The Southern High Plains of Texas occupies an area of about 22,000 square miles in northwest Texas, extending from the Canadian River southward. about 250 miles and from the New Mexico line eastward an average distance of about 120 miles. The economy of the area is dependent largely upon irrigated agriculture, and in 1958 about 44,000 irrigation wells were in operation. The economy of the area is also dependent upon the oil industry either in the form of oil and gas production or in the form of industries based on the production of petroleum. The Southern High Plains of Texas is characterized by a nearly flat land surface sloping gently toward the southeast at an average of 8 to 10 feet per mile. Shallow undrained depressions or playas are characteristic of the plains surface, and during periods of heavy rainfall, runoff collects in the depressions to form temporary ponds or lakes. Stream drainage on the plains surface is poorly developed; water discharges over the eastern escarpment off the plains only during periods of excessive rainfall. The climate of the area is semiarid; the average annual precipitation is about 20 inches. About 70 percent of the precipitation falls during the growing season from April to September. Rocks of Permian age underlie the entire area and consist chiefly of red sandstone and shale containing numerous beds of gypsum and dolomite. The Permian rocks are not a source of water in the Southern High Plains, and any water in these rocks would probably be saline. The Triassic rocks underlying the Southern High Plains consist of three formations of the Dockum group: the Tecovas formation, the Santa Rosa sandstone. and the Chinle formation equivalent. The Tecovas and Chinle formation equivalent both consist chiefly of shale and sandy shale; however, the Santa Rosa sandstone consists mainly of medium to coarse conglomeratic sandstone containing some shale. The formations of the Dockum group are capable of yielding small to moderate quantities of water in many parts of the Southern High Plains; however, in practically all places the water is rather saline and probably unsuitable for most uses. The Cretaceous formations in the Southern High Plains consist of several formations of the Trinity, Fredericksburg, and Washita groups. The rocks underlie a large part of the southern part of the Southern High Plains; they consist of sandstone, shale, and limestone, the sandstone and limestone being the principal water-bearing units. In a few places where the Cretaceous rocks appear to be in hydraulic connection with the overlying Ogallala formation, moderate quantities of water are obtained, particularly from the limestones. Locally the Cretaceous rocks may be important aquifers where other water is not available, but they generally do not constitute a large source of water for irrigation or municipal use. The Ogallala formation of Pliocene age is the principal aquifer in the Southern High Plains of Texas; it supplies practically all the water used for all purposes. The formation is continuous throughout most of the Texas part of the Southern High Plains and extends into New Mexico. The .formation consists chiefly of sediments deposited by streams that had their headwaters in the mountainous regions to the west and northwest. The Ogallala formation rests unconformably upon an erosional surface of the underlying Triassic and Cretaceous rocks. The Ogallala consists of beds and lenses of clay, silt, sand, and gravel; caliche occurs as a secondary deposit ,in many places in the formation. In general the Ogallala is thicker in the northern part of the area; the thickness ranges from 400 to 500 feet in central Parmer, west-central Castro, and southwestern Floyd Counties to a knife edge where the formation wedges out against outcrops of the older rocks.
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Hale County, in the southern High Plains of Texas, has an area of 1,033 square miles. The land surface is one of low relief, and the regional slope is about 10 feet per mile toward the southeast. Surface runoff drains into numerous playa lakes and two intermittent streams: Running Water Draw and the Double Mountain Fork of the Brazos River. The Ogallala formation of Tertiary age is the principal water-bearing formation in the county. The Ogallala lies on red beds of Triassic age throughout most of the county and on rocks of Cretaceous age in approximately the southern fifth of the county. The Triassic and underlying Permian rocks are not fresh water bearing in the county. The Cretaceous rocks, on the other hand, are in direct hydraulic connection with the Ogallala, and a few wells tapping them yield large quantities of water from cracks and solution channels in the limestones. The Ogallala formation is overlain by thin deposits of sand, gravel, silt, and clay of Pleistocene and Recent age. These younger rocks are, for the most part, above the water table and, consequently, are not water bearing. The water in the Ogallala formation occurs principally as unconfined water in layers and lenses of sand and gravel. The hydraulic properties of the Ogallala were determined by a long-term aquifer test at Plainview, where coefficients of transmissibility ranging from 24,000 to 38,000 gpd per foot were measured. The coefficient of storage was determined to be about 0.14. The aquifer is recharged from precipitation in Hale County and in the southern High Plains northwest of the county. The water moves generally southeastward at about 2 inches a day. Ground water in Hale County is used principally for irrigation. In 1955 more than 3,700 wells were used to irrigate 470,000 acres; about 560,000 acre-feet of water was pumped. About 5,000 acre-feet was pumped for other purposes, including municipal, industrial, stock, and domestic uses. The water in the Ogallala formation in Hale County is suitable chemically for irrigation and most other uses; however, it should be softened for more satisfactory domestic use. The high silica content indicates that the water may be unsuitable for use in boilers. The fluoride content is excessive. It is estimated that in 1955 about 39 million acre-feet of water was in storage in the Ogallala formation in Hale County; however, only about 16 million is theoretically available to wells, and a somewhat smaller amount is practically available. About 3 million acre-feet was removed from storage during 1938-55. Water levels in wells have declined more or less steadily since 1938, and it is apparent that the ground-water resources of the county are insufficient to support large-scale perennial irrigation such as that of 1955.
No abstract available.