Development of Quantified Water Rights,
Mescalero Apache Reservation, New Mexico

Situation

Development of groundwater resources for Indian tribes in the west revolves around Winters Doctrine rights and the McCarran Amendment, which established Practical Irrigable Acreage (PIA) as the yardstick to quantify water rights. PIA claims are a complex interrelationship among economic, hydrogeologic, market, agricultural, and social factors. The hydrogeologic challenge is to work closely with tribal leaders, economists, agronomists, and soil scientists to jointly develop appropriately scaled and economically viable irrigation projects.

Objectives

Hydro Geo Chem, Inc. performed a hydrologic evaluation of a proposed wellfield on the Mescalero Apache Indian Reservation, a source area for the Roswell Groundwater Basin. The proposed wellfield will withdraw 10,000 acre-feet annually from the Permian aquifer that comprises part of the groundwater basin and sustains perennial flow to several streams. Project objectives were to predict the effects of wellfield pumping on stream flows and groundwater levels within the groundwater basin. An extensive data collection and interpretation effort was used to design and calibrate the numerical model. The model consisted of three layers and included numerous stream reaches. An automatic parameter estimation model (INVERS), that accounted for uncertainty in both recharge and transmissivity, was utilized to assist in calibration and to provide a sensitivity analysis of the estimated parameters.

Hydro Geo Chem developed a groundwater flow model to simulate the effects of pumpage from the San Andreas Formation on lakes and streams near the Village of Rio Ruidoso.

Results

The results of the simulations, which were performed using the McDonald-Harbaugh (USGS) finite-difference model, were presented in evidence in the case of New Mexico vs Lewis in New Mexico District Court.