Ground-water resources of the Houston district, Texas

Abstract

This report covers the current phase of an investigation of the supply of ground water available for the Houston district and adjacent region, Texas,- that has been in progress during the past 10 years. The field operations included routine inventories of pumpage, measurements of water levels in observation wells and collection of other hydrologic data, pumping tests on 21 city-owned wells to determine coefficients of permeability and storage, and the drilling of 13 deep test wells in unexplored parts of the district. Considerable attention has been given to studies of the location of areas or beds of sand that contain salt water. The ground water occurs in beds of sand, sandstone, and gravel of Miocene, Pliocene, and Pleistocene age. These formations crop out in belts that dip southeastward from their outcrop areas and are encountered by wells at progressively greater depths toward the southeast. The beds throughout the section are lithologically similar, and there is little agreement among geologists as to their correlation. -In this investigation, however, the sediments, penetrated by the wells are separated into six zones, chiefly on the basis of electrical logs. Most of the water occurs in zone 3, which ranges in thickness from 800 to 1,200 feet. Large quantities of ground water are pumped in three areas in the Houston district, as follows: The Houston tromping area, which includes Houston and the areas immediately adjacent; the Pasadena pumping area, which includes the industrial section extending along the ship channel from the Houston city limits eastward to Deer Park; and the Katy pumping area, an irregular-shaped area of several hundred square miles, which is roughly centered around the town of Katy, 30 miles west of Houston. In 1930 the total combined withdrawal of ground water in the Houston and Pasadena pumping areas averaged about 50 million gallons a day. It declined somewhat during 1932 and 1933 and then gradually increased, until in 1935 the total pumpage was about the same as it was in 1930. About March 1, 1937, the pumpage was increased by about 40 percent, when new wells near Pasadena were put into operation. During 1940 it is estimated that the total pumpage in the Houston and Pasadena areas averaged about 79 million gallons a day, an increase of about 65 percent over the pumpage in 1935. About 25 million gallons of this increase has occurred in the Pasadena area. In the Katy rice-growing area the pumpage in 1935 was about 14 million gallons a day; in 1937 it was about 30 million gallons a day; in 1939 about 40 million gallons a day; and in 1940 about 45 million gallons a day. In 1940 the estimated total pumpage from the Houston, Pasadena, and Katy pumping areas was about 124 million gallons a day, or twice as much as it was in 1935. The increase in pumping at Pasadena in the spring-of 1937 caused the water leveling wells in the Houston and Pasadena areas, which had not varied materially for about 7 years, to decline at a rapid rate. Further increases in the pumping both at Houston and Pasadena in 1939 and 1940 has caused further substantial decline. The water levels in wells in the Katy rice-growing area also declined materially. The evidence points to the probability that in all parts of the Houston district, except the Katy rice-growing area, the rainfall is recharging the aquifers at a rate greater than that at which the water is transmitted down the dip. In the Katy area the recharge is insufficient to balance the joint discharge by transmission down the dip and withdrawal from rice-irrigating wells. The average coefficient of transmissibility was. calculated as 160,000 gallons a day. On the basis of these estimates the inflow in February 1940 across the artesian contour 10 feet below sea level (see pl. 10) was computed as 72 million gallons a day. The amount of water taken out of artesian storage in the 300-square mile area within the -10 contour during the period February 1939 to February