GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 96-32
Presentation Time: 9:00 AM-6:30 PM

CHARACTERIZING INTERACTIONS BETWEEN SURFACE AND GROUNDWATER IN THE GREAT MIAMI VALLEY WATERSHED USING STABLE ISOTOPE AND CHEMICAL ANALYSIS


JOHNSTONE, Caroline, Geology Department, University of Dayton, 300 College Park, Dayton, OH 45409-2364 and BEDASO, Zelalem K., Department of Geology, University of Dayton, 300 College Park, Dayton, OH 45469

Groundwater-surface water interaction play a vital role in determining the quality and quantity of groundwater as well as sustainable water resources management. Surface water and groundwater are key components in the water cycle that variably interact depending on geology, topography, and rainfall seasonality. We use environmental isotopes of Hydrogen (δD) and Oxygen (δ18O), which are conservative dual tracers, to provide key information on the movement and flux of water in the hydrologic cycle, degree of mixing between reservoirs, and spatial and seasonal variation of surface and groundwater interaction. Here we examine the degree of surface and groundwater interaction in the Great Miami Valley Watershed (GMVW). Weekly precipitation samples from Dayton, OH, spring and fall groundwater samples from the Great Miami Buried Aquifer and weekly river water samples from four locations (Still Water River, Mad River, and two locations on the Great Miami River) were collected and analyzed for δD and δ18O. Our initial data set shows that the average isotopic composition of the rivers is -6.9±0.15 for δ18O and -44.3±0.98 for δD during the warm season and -7.3±0.59‰ for δ18O and -46.3±4.9‰ for δD during the cool season.The average isotopic composition for groundwater is -7.0±0.63 for δ18O and -44.3±3.4 for δD during the spring and -6.8±0.74‰ for δ18O and -43.3±4.1‰ for δD during the fall. Our result based on an isotope two-component mixing model shows high degree of connectivity between surface and groundwater in the Miami Valley. Locally, rivers and the Great Miami Buried Aquifer shows more than 75% mixing. The outcome of this study will provide useful information on available seasonal groundwater recharge and help to determine the impact of anthropogenic activity and the effect of climate change on water balance in the GMVW.

Key words: isotope, surface water, groundwater, water quality, Miami valley