SIMULATION OF THE AQUIFER SYSTEM IN PART OF THE HONDO BASIN FROM THE SIERRA BLANCA TO RIVERSIDE, NEW MEXICO

We describe a three-dimensional numerical model of groundwater flow in part of the Rio Hondo Basin from the Sierra Blanca to Riverside, New Mexico. The model is designed for the purpose of assessing the hydrologic response to water use in the region of the Hondo Basin. The model is under development as additional information becomes available.

The model area refers to the geographic extent that includes the valley between the Sacramento and the Capitan mountains and hydrogeologic features downstream to Riverside. The model covers an area of 880 square miles in Lincoln and Otero counties. The elevation of the water table ranges from over 9,000 feet in the Sacramento Mountians to about 4,800 feet near Riverside. Average annual precipitation ranges from 32 to 12 inches.

Generalized hydraulic parameters are modeled using the Hydrogeologic-Unit Flow Package 2 (Anderman and Hill, 2003), which is based on a three dimensional solids model of the aquifer system. The model includes 13 generalized Hydrogeologic Units identified for the model area including: Recent Alluvium (Qal) along Rio Ruidoso, Rio Bonito and Rio Hondo; shallow and deep Sierra Blanca Volcanics (Tv), the Cub Mountain Formation (Tcm), the Mesaverde Group (Kmv), Mancos Shale (Km), a combined Dakota-Santa Rosa unit (KdTr), the Grayburg (Artesia) Formation (Pg); an upper, middle and lower San-Andres Formation (Psa); The Yeso Formation (Py) and Pre-Cambrian crystalline and Pre-Permian rock units (PPc).

The calibrated steady-state correlation between simulated and observed heads reflects an RMS error of 74 feet and R² of 0.99. The model simulates seasonal and annual hydrologic features that define the interaction of the regional aquifer system: natural recharge, evapotranspiration (ET), spring discharge and water routing through streams and farms. The model represents a combination of structural hydrogeologic units merged with a general representation of regional recharge to simulate the aquifer system. Combining the structural system with a general hydrologic component resulted in a functional model representative of conditions observed in the field in a relatively short time frame.