3-D Hydrostratigraphic Models of Countywide Groundwater Resources in the Texas Panhandle

Texas Senate Bill 1763 requires that by September 2010 each of its 254 counties declare a Desired Future Condition (DFC) of its groundwater through 2060.  Many groundwater management areas and/or counties are scrambling to better understand the impact of groundwater level fluctuations on stream and spring flows, and groundwater availability for future irrigation and municipal demands.  Daniel B. Stephens & Associates, Inc. (DBS&A) has completed 3-D hydrostratigraphic analyses of three counties (Hemphill, Parmer, and Dawson, each 900 mi²) in the Texas Panhandle that are totally dependent on groundwater from the Ogallala, Edwards-Trinity/High Plains and/or Dockum aquifers.  The hydrostratigraphic analysis involved lithologic and stratigraphic interpretations and integration of between 300 to 700 driller’s reports and geophysical logs into a 3-D framework using ArcGIS and CTech’s Mining Visualization System (MVS).  Driller’s reports selected were screened for location accuracy, well depth, detail of lithologic description, and production interval, with approximately 30% passing screening criteria.  Recent water levels were used to create a 3-D piezometric surface within the hydrostratigraphic model and saturate the delineated stratigraphy.  Hemphill County collected more than 250 synoptic water levels to create a high-resolution, 3-D water-level surface to investigate groundwater - surface water interaction and spring flow.  A 3-D decade, water-level-decline, time sequence (1958 to 2008) was created for Parmer County which illustrated the geospatial groundwater decline of almost 60% of the 1958 gross saturated thickness during this 50 year period.  Dawson County was able to better understand its groundwater availability and water level fluctuations within the different aquifers using the 3-D model.  Groundwater in storage volumetrics were also calculated for each county to assist with DFC selection.