New Mexico Geological Society Annual Spring Meeting — Abstracts

Ground water is one of New Mexico's most important geological resources. Ground water supplies 90% of the State's drinking water and supports perennial stream flow as well as our limited but treasured riparian areas. Ground water is not a nonrenewable resource like a mineral deposit or a petroleum reserve, but neither is it completely renewable. Ground water resources may appear ample, but availability varies widely and only a portion of ground water can be withdrawn economically and without adverse consequences. In the past decade, attention has turned to sustainable development of ground water (and surface water) -that is development in a manner that can be maintained indefinitely without causing unacceptable environmental, economic, or social consequences.

Under natural conditions, aquifers are in a state of dynamic equilibrium -recharge approximately equals discharge. Recharge from precipitation continually replenishes ground water, but typically at much smaller rates than rates of withdrawal, and in New Mexico the amount of recharge is both small and relatively fixed. Estimates of areal recharge range from 0.03% to 20% of mean annual precipitation, depending on evaporation, soil, vegetation, and slope conditions. Significant recharge is extremely localized along streams, arroyos, mountain fronts, and faults. Accordingly, the primary sources of pumped ground water are aquifer storage, decreased discharge to streams, and decreased transpiration by plants.

In some areas of New Mexico, decades of pumping have resulted in significant depletions of ground-water storage and declining water tables indicative of "ground-water mining". Water level declines of up to 140 feet occurred in the Albuquerque area between 1960 and 1992, a condition that will ultimately reduce flow in the Rio Grande, and may impact drinking water supplies, riparian bosque, critical habitat, and land subsidence. Other mined basins include the Mimbres, Estancia, and Espanola Basins, and the Ogallala aquifer. Tradeoffs between ground-water consumption and undesirable environmental and economic effects have become the driving force in the State Engineer's recent development of administrative guidelines for management of ground water in the middle Rio Grande Basin.