Recharge to Pajarito Plateau regional aquifer system
— David B. Rogers, Alan K. Stoker, Stephen G. McLin, and Bruce M. Gallaher

We present a picture of water balance in the Pajarito Plateau regional aquifer system based on a synthesis of geochemical and water level information and prior work. Assuming that water table rather than confined aquifer conditions apply, depletion of the Pajarito Plateau regional aquifer system based on limited water level data appears to equal total pumping for water supply for the period 1950-1993. This suggests that aquifer recharge could be far smaller than withdrawal of water, and that the resource is being mined. Carbon-14 data indicate that the age of aquifer water ranges from about 1000 to more than 35,000 years and that age increases towards the Rio Grande. These data support the possibility that part of the aquifer is recharged from the Sangre de Cristo Mountains, and that a groundwater divide in the aquifer lies west of the Rio Grande. In other cases, tritium detected at trace levels shows the presence of minor recent recharge to the top of the aquifer, particularly beneath canyons on the Pajarito Plateau.