GROUNDWATER CIRCULATION IN MOUNTAIN BLOCKS ADJACENT THE RIO GRANDE RIFT

Three areas along the eastern front of the Rio Grande rift are presented to describe regional scale structural and stratigraphic controls on groundwater flow in fractured mountain-block aquifers. A regional scale conceptual model of groundwater flow in these mountain blocks was developed using simple geostatistical and geochemical methods to define unique hydrostructural domains. Continuous Paleozoic carbonate dipslopes and extension related fault and fold belts comprise two regional hydrostructural domains that are uniquely defined based on (1) geochemical time-series analysis in the Sandia Mountains, (2) historical isotope characterization of the Sacramento Mountains, and (3) kriging of yield-residual data from the Sangre de Cristo Mountains.

In each of the three study areas, only limited fracture or hydrologic data were available to predict regional permeability distributions. The hydrostructural domain approach used in this study provided evidence of regional permeability to understand the timing and distribution of recharge to montane aquifers bounding the Rio Grande rift. Defining the control that structural and stratigraphic heterogeneities have on the hydrology of mountain blocks can be problematic, because folding, faulting, and fracturing of aquifers has the potential to significantly influence groundwater flow at both local and regional scales. The results from statistical analyses of geochemical and well yield data provided an initial assessment of heterogeneities controlling regional hydrology.