Ground water level studies at Lagrave field monitoring wells and their sensitivity to recharge from rainfall and the Trinity River, Fort Worth, Texas

This project was launched with the key objectives of studying the characteristics of the aquifer at the Paddock bend floodplain and its reaction to possible recharges from falling rainfall and the nearby Trinity River.; This aquifer is composed of different alluvial layers such as silt, clay and sand which are perched on top of a layer of relatively impermeable limestone. They are in hydraulic contact with the Trinity River and they have a variable vertical and aerial extent. An attempt made to estimate the hydraulic conductivity suggests that this alluvial aquifer has a very low (70.4m/year) hydraulic conductivity which is related to its clay-silt dominated subsurface composition.; Groundwater is encountered at a depth of 9 to 25 ft below the ground surface with the highest elevation (525 ft above mean seal level) of the water table on the western part of the project site. The water level map and the data collected through the monitoring network in the area show that groundwater flows in a northeasterly direction toward the Trinity River.; Detailed analysis of the water level hydrographs and hourly rainfall hyetographs for the period of this research show the seasonal fluctuation of the water level in the aquifer with water level falling in the summer and then rising in the fall. Furthermore, the strong correlation of the water level changes with the rainfall suggests that such water level changes are the result of groundwater recharge from the percolating rain. Such water level rises from individual storm events, however, are very small compared to the amount of rainfall and the aquifer response is slow and the water level changes are small due to due to the low degree of infiltration of rainwater from through the aquifer materials.; Groundwater recharge from the Trinity River seems to have a very negligible effect on the water level in view of their hydraulic head differences as well as the hydraulic conductivity of the aquifer materials which are in contact with Trinity River. During the period of this research, the Trinity River Elevation remained almost stable through time while the groundwater elevations became very low during summer and early fall. Therefore, there could have been slight degree of groundwater recharge from the river during such dry seasons where the rate of evapotranspiration is very high and the amount of rainfall is very low.