Regional decline of aquifer head due to ground-water withdrawal in the Houston area has caused extensive land-surface subsidence. The NASA-Johnson Space Center (NASA-JSC) in southeastern Harris County, Texas, was about 13 to 19 feet above mean sea level in 1974 and sinking at a rate of more than 0.2 foot per year. NASA-JSC officials, concerned about the hurricane flooding hazard, requested the U.S. Geological Survey to study the feasibility of artificially recharging the aquifers for subsidence abatement. Hydrologic digital models were developed for theoretical determinations of quantities of water needed, under various well-array plans, for artificial recharge of the Chicot and Evangeline aquifers in order to halt the local subsidence at NASA-JSC. The programs for the models were developed for analysis of three-dimensional ground-water flow. Total injection rates of between 2,000 and 14,000 gallons per minute under three general well-array plans were determined for a range of residual clay pore pressures of 10 to 70 feet of hydraulic head. The space distributions of the resultant hydraulic heads, illustrated for injection rates of 3,600 and 8 ,400 gallons per minute, indicated that, for the same rate, increasing the number and spread of the injection locations reduces the head gradients within NASA-JSC. (Woodard-USGS)
