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A groundwater potentiometric surface map was generated from the March 2001 groundwater elevations and is shown in Figure 1.� The March 2001 potentiometric surface map indicates that the general groundwater flow direction was to the southeast with a gradient of approximately 0.0125 feet/feet.� Groundwater flow directions and gradients during past monitoring events are provided in Table 3 of the Introduction to the Groundwater Monitoring Program at Camp Stanley for comparison.
Several features of the March 2001 potentiometric surface map (Figure 1) should be noted.� The water level measurements indicate that groundwater elevations were highest in the northwestern portion of the inner cantonment area and decreased towards both southeast and northeast.� The water level data exhibit relatively lower groundwater elevations in the north pasture.� Wells G and I in the north pasture had the lowest groundwater elevations of any CSSA wells during the March 2001 sampling event.� The natural groundwater gradient at CSSA is typically towards the southeast so Wells G and I have therefore generally had higher water levels than wells located in the inner cantonment area.
Due to discrepancies with water levels in surrounding wells, water levels from Wells 10 and 16 were excluded from the potentiometric map.� The groundwater elevation in Well 10, which was measured via the air-line method, was approximately 60 feet below the groundwater elevation in Well 9 and 67 feet below that measured in Well 11.� The groundwater elevation of 1150.96 feet MSL in Well 16, which was 10 feet lower than the water level in Well D, was much lower than water levels in nearby wells.� Interpretation of the water level data was simplified by excluding these data and the potentiometric surface could be drawn in a more conservative and general fashion.
The water level in Well 10 may be lower than surrounding wells because it is an active water supply well and is frequently pumped.� The differences in water levels in Well 16 and surrounding wells may stem from differences in the way these wells are completed.� Wells 2, 3, 4, MW-1, and MW-2 are completed in either the Lower Glen Rose or Lower Glen Rose and upper portion of the Bexar Shale.� Well 16 is open in the Lower Glen Rose, Bexar Shale and Cow Creek.
As shown in Figure 1, water levels in the central portion of CSSA show much variability.� This variability is likely associated with three factors: 1) differences in well completion depths and formations penetrated; 2) differences in recharge rates due to increased secondary porosity associated with the Salado Creek floodplain; and 3) differences in recharge rates due to increased secondary porosity associated with the fault zone.� As discussed in the Introduction to the Groundwater Monitoring Program, all of the potentiometric surface maps prepared to date for CSSA are based on water levels in 13 wells with different completion depths.� Several wells are open to multiple water-bearing zones; therefore, contour maps should be considered qualitatively.