An important gap in the understanding of the hydrology of the Middle Rio Grande Basin, central New Mexico, is the rate at which water from the Rio Grande recharges the Santa Fe Group aquifer system. Though several methodologies have been applied to the problem, they yield a wide range of estimates. A study by the U.S. Geological Survey (USGS) is using water-temperature methods to quantify horizontal and vertical ground-water fluxes from the Rio Grande, horizontal and vertical hydraulic conductivities of the post-Santa Fe Group valley and basin-fill deposits, and ground-water fluxes into the riverside drains.

Eight piezometer nests were installed in an east-trending line across the Rio Grande, north of the Paseo del Norte bridge in Albuquerque, to collect temperature- and hydraulic-gradient data between March 1999 and July 2000. The piezometer nests are located between the Corrales Riverside drain (on the west side of the Rio Grande) and the Albuquerque Riverside drain (on the east side of the Rio Grande). Each piezometer nest consists of three piezometers installed approximately 3, 7, and 13 meters below land surface. Automated data loggers collected ground-water temperatures at five depths (approximately 2, 4, 6, 8, and 11 meters) in each piezometer nest at 60-minute sampling intervals. Also, ground-water levels were measured monthly in each piezometer nest. In addition, data loggers collected surface-water temperatures in each drain and in the Rio Grande. Finally, stage measurements of the Rio Grande were collected at the USGS streamflow-gaging station (Rio Grande near Alameda—08329928), located immediately south of the Paseo del Norte bridge. Data are being analyzed using the two-dimensional heat- and water-transport model VS2DH to estimate directions and rates of ground-water flow beneath this section of the Rio Grande.