Aquifer tests in the flood-plain alluvium and Santa Fe group at the Rio Grande near Canutillo, El Paso County, Texas

Abstract

An aquifer system consisting of the Rio Grande flood-plain alluvium and Santa Fe Group underlying the southern Mesilla Valley in Dona Ana County, New Mexico, and El Paso County, Texas, has become an important source of water for municipal and agricultural uses. The Rio Grande is hydraulically connected to the shallow flood-plain alluvium. Determination of aquifer properties is essential in order to evaluate the potential for ground water to meet increasing water demand and the potential streamflow depletion of the Rio Grande caused by ground-water development. The aquifer system at the Canutillo well field hydrologic section was divided into a shallow, upper intermediate, lower intermediate, and deep zone on the basis of geohydrologic characteristics. Aquifer properties of specific zones at the test site were determined from a series of multiple-well aquifer tests conducted from December 3, 1985, through January 20, 1986. Water within the shallow zone generally occurs under unconfined conditions and within the upper intermediate, lower intermediate, and deep zones under leaky-confined conditions. The estimated hydraulic diffusivity of the shallow zone is 175,000 feet squared per day. Estimated aquifer properties of the upper intermediate zone from 97 to 200 feet below land surface are as follows: (1) transmissivity, 2,600 feet squared per day; (2) storage coefficient, 4.3 x 10; (3) hydraulic conductivity, 26 feet per day; and (4) vertical hydraulic conductivity of the upper confining unit, 0.16 foot per day. Estimated aquifer properties of the deep zone are as follows: (1) transmissivity, less than or equal to 4,700 feet squared per day; (2) storage coefficient, less than or equal to 4.3 x 10 ; (3) hydraulic conductivity, less than or equal to 11 feet per day; and (4) vertical hydraulic conductivity of the upper confining layer, less than 0.01 foot per day.