Diminishing groundwater supplies will severely reduce regional crop and animal production in the Northern High Plains of Texas where irrigated crop production accounts for a major portion of groundwater withdrawals from the Ogallala Aquifer. The objective of this study was to develop, calibrate and validate a groundwater model for a four-county area (Dallam, Sherman, Hartley, and Moore counties) in the Northwest region of the Texas High Plains. This study is a major component of a comprehensive regional analysis of groundwater depletion in the Ogallala Aquifer region with the purpose of understanding short- and long-term effects of existing and alternative land use scenarios on groundwater changes. Hydrologic simulations were conducted using the MODFLOW-2000. The model was calibrated for predevelopment period by reproducing and comparing groundwater levels of the 1950s using steady state boundary conditions representing no change in the land use. Similarly, the model was calibrated for the period 1950-2000 with a transient model to account for agricultural development occurred during that period. The model was validated by simulating and comparing ground water levels with the observed data for the period 2001-2008. Calibration and validation results indicate that model performed satisfactorily. The calibrated model will be used to evaluate the effects of change in land use/land cover on sustainability of the aquifer life in the Texas High Plains.