4 research outputs found
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Numerical Modeling of Regional Ground Water Flow in the Deep-Brine Aquifers of the Palo Duro Basin, Texas Panhandle
A conceptual hydrogeologic model of the Palo Duro Basin, Texas Panhandle, subdivides the basin into three hydrogeologic units: the shallow Ogallala and Dockum aquifers, the Permian evaporite aquitard, and the deep confined, underpressured Permian and Pennsylvanian brine aquifer. The first permeable units beneath the thick Permian evaporite section are Wolfcamp strata composed of carbonates, shales, and arkosic sand and gravels (granite wash) with average effective permeability values of 8.9, 0.0001, and 8.6 md, respectively. Groundwaters in the Wolfcamp aquifer flow to the northeast toward the semi-impermeable, granitic Amarillo Uplift. This anomalous hydrologic condition (flow toward a low-transmissivity barrier) may result from the presence of highly permeable granite-wash deposits that flank the uplift and function as "hydrologic sinks."
A two-dimensional, vertical-averaging finite-element model, incorporating the different lithologies and their different permeabilities as well as leakage through the overlying evaporite aquitard, has been used to simulate the observed potentiometric surface of the Wolfcamp aquifer. The conditions that best simulate the observed Wolfcamp potentiometric surface are a combination of specified head and no-flow conditions along the uplift, permeability values greater than 260 md for the granite-wash deposits that flank the uplift (in contrast to the average value of 8.6 md), and an increased permeability value of 50 md for the highly porous carbonate zone. The best estimate of the vertical permeability of the evaporite aquitard is 0.00008 md.
Treating the whole deep-brine aquifer as a single permeable unit beneath the evaporite aquitard, groundwater flow is to the northeast toward the uplift with a slightly larger west-to-east component than that found when considering only flow in Wolfcamp strata. The conditions that best simulate the averaged potentiometric surface are those from the best simulation of Wolfcamp strata, with increased permeability values of 260 md for the Pennsylvanian granite-wash close to the uplift and 250 md for the high-porosity Pennsylvanian sandstone.Bureau of Economic Geolog
Suitability of SWAT Model for Simulating of Monthly Streamflow in Lam Sonthi Watershed
AbstractThe purpose of this study was to simulate the hydrologic processes from a watershed using the âSoil and WaterAssessment Toolâ (SWAT) model approach. The model was evaluated with the purpose to simulate the streamflows in an agricultural watershed in central Thailand. The results showed that the coefficient of correlation (R2) and the Nash-Sutcliffe coefficient (ENS) values were raised above 0.7, and the deviation of runoff volumes (Dv) was also acceptably accurate. Some months of simulated flows were overestimated but most simulated flows were close to observed flow by both the graphic and the statistical approaches. Although the model was evaluated using limited data and some of the modelâs algorithms for calculating flows might not be appropriate for tropical conditions like the watershed, overall prediction results were within acceptable levels for estimating monthly flows. This led to the conclusion that the SWAT model can reliably predict monthly streamflows on any other agricultural watershed in tropical climates with conditions similar to the watershed studied
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Porosity Distribution Trends in WolfCamp Strata of the Palo Duro Basin, Texas Panhandle Implications for Ground Water.
Average porosity distributions in the Wolfcamp deep-basin aquifer are studied to discern the geographic trends in effective porosity throughout the Palo Duro Basin. Highly resolved, log-derived porosity data are used to improve porosity resolution in computer-simulated areal groundwater modeling. Assessing vertical distributions of lithology and porosity in each of the wells studied involves cross-plotted neutron and density porosity log responses, which more accurately identify lithology and porosity than cross-plotted neutron porosity and acoustic (interval travel time) responses. Subsequent analyses of log-derived porosity distributions yield information about the total effective pore volume (movable water) in the Wolfcamp aquifer, in addition to enhancing the accuracy of estimating deep-brine velocities and travel times in its basin-wide traverse. Northeastward, basin-wide travel times range between 2.5 x 10^5 and 2.0 x 10^6 years, indicating the potential frequency of basin flushing across the basin.Bureau of Economic Geolog