Groundwater Study at Armand Bayou Nature Center

Abstract

This paper describes the research done to determine the hydraulic gradient and direction of groundwater flow in two aquifers at the Armand Bayou wetland. One aquifer is an unconfined aquifer at a depth of approximately 15 ft. and the second aquifer is a perched aquifer near the surface. The wetland research site was located at the Armand Bayou Nature Center near Houston, Texas. Four well nests were installed at this site. Each well nest consisted of a deep well (13-16 feet deep) installed below a thick clay lense and a shallow well (1-2 feet deep) installed above the clay lense. The groundwater levels were measured once a week over a two year period at all four well nests. Water levels in Armand Bayou were also measured. The first year the data was recorded was a wet year (17.81 inches of rainfall over collection period) and the second year was an unusually dry year (5.8 inches of rainfall over collection period). The paper presents how the hydraulic gradient and direction of groundwater flow changed during a drought. The data showed that the typical direction of flow in the aquifers was toward the bayou and that under drought conditions the direction of flow was altered by an average of 10.1˚. The drought conditions also caused the hydraulic gradient to decrease by an average of 0.00254 ft. / ft.