QUANTIFICATION OF GROUNDWATER-SURFACE WATER INTERACTIONS THROUGH HYPORHEIC FLOW STUDY IN LOWER RIO GRANDE, TX

Groundwater-Surface water interactions in streams are inherently complex making them difficult to measure or predict. Factors such as climate, riparian vegetation, heterogeneous subsurface and anthropogenic structures, e.g., dams and canals, add more complexity. These interactions impact aquatic ecosystems’ health as water flow influence temperature, nutrient availability, and water quality. Oxbow lakes and cut-off meandering channels in South Texas, a.k.a. “Resacas”, are largely understudied. The aim of this study was to characterize subsurface geologic profiles at selected sites and to analyze potential interactions with Rio Grande River and different Resaca systems, which can be possible indicators for groundwater-surface water interactions. Preliminary subsurface characterizations were studied using Rockworks software with drillers’ report and lithology data from the Texas Water Development Board groundwater database. A series cross-sections showed a complex fluvial sedimentary environment with heterogenous settings. Geophysical survey and field boreholes are planned to provide additional sediment and groundwater information as potential hydrogeochemical indicators. The data obtained will be integrated in a GIS-based framework for regional water resource management planning under extreme conditions e.g. droughts or floods.