|MAREK, THOMAS - Texas Agrilife Research|
Submitted to: Texas Water Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2013
Publication Date: 3/1/2013
Citation: Hernandez, J.E., Gowda, P., Marek, T.H., Howell, T.A., Ha, W. 2013. Groundwater levels in Northern Texas High Plains:Baseline for existing agricultural management practices. Texas Water Journal. 4(1):22-34.
Interpretive Summary: The economy in the northern High Plains of Texas is based on water that is available for plants. This area uses water from the ground for plants and this water comes from the Ogallala Aquifer. Water levels in the Ogallala Aquifer are declining. Creating a model is one way to learn about water use. This model has the ability of predicting future water levels, and it shows that people will be spending more for pumping water during the next 50 years if the current use of the Ogallala Aquifer is not modified. Two zones were identified that will be depleted below economic pumping water depths and would therefore cause rising costs. These areas are located in east Hartley County of Texas and close to the northwest corner of the same county.
Technical Abstract: New groundwater policies are being debated for the northern High Plains of Texas due to the depletion of the underlying Ogallala Aquifer, the major source of water for irrigation, and they should be thoroughly evaluated using a calibrated groundwater model for assessing the impact on subsequent groundwater levels. The objectives of this study were to (1) calibrate and validate an integrated regional groundwater model using observed groundwater levels between 1937 and 2007, and (2) predict the impact of the existing agricultural management policy on groundwater levels in the Ogallala Aquifer beneath four heavily irrigated counties (Dallam, Sherman, Hartley, and Moore) located in the northwest corner of the northern High Plains of Texas. For this purpose, the study area was divided into 800 x 800 m cells and the ModFlow-2000 model was calibrated and validated. Results indicated that the groundwater model was calibrated and validated satisfactorily based on reproducing and comparing groundwater levels with coefficients of determination of 0.97 and 0.98, root mean square errors of 28.0 m and 15.5 m, and normalized root mean square errors of 6.9% and 4.3%, for calibration and validation, respectively. Analysis of prediction results indicated that two zones would become depleted below economic pumping water depths for irrigation, if the current aquifer exploitation continues with no modification during the next 50 years. These areas are located in east Hartley County and close to the northwest corner of the same county. The calibrated model should assist water managers to evaluate the implications of alternative agricultural management policy scenarios on groundwater levels between 2010 and 2060 and to define specific irrigation water practices, to promote the use of alternative technologies in the four-county area, and to potentially implement new policies for sustainable irrigation from the Ogallala Aquifer.