The regional groundwater flow system in the carbonate rocks of Nevada and Utah is conceptualized as shallow systems superimposed on deeper systems, which transmit water primarily through carbonate rocks. A computer model was used to simulate the two systems. The regional model includes simplifying assumptions that are probably valid for parts of the province; however, the validity of each assumption is unknown for the province as a whole. Therefore, simulation results do not perfectly replicate actual groundwater flow; instead they provide a conceptual evaluation of regional groundwater flow. The model was calibrated by adjusting transmissivity and vertical leakance until simulated water levels and simulated discharge generally agreed with known water levels, mapped areas of discharge, and estimates of discharge. Simulated flow is about 1.5 million acre-ft/yr. Most groundwater flow is simulated in the upper model layer where about 45 shallow flow regions were identified. In the lower layer, 17 deep-flow subregions were identified and grouped into 5 large regions on the basis of water-flow patterns. Simulated flow in this layer is about 28 percent of the total inflow and about half is discharged as springflow. Interbasin flow to several large springs is through thick, continuous, permeable carbonate rocks; elsewhere deep consolidated rocks are not highly transmissive, suggesting that carbonate rocks are not highly permeable everywhere or are not present everywhere. (USGS)
