ABSTRACT:

Rivers are integrators of hydrologic responses and catchment activity that are rich in information on watershed processes. Particularly, concentration-discharge (C-Q) relationships produce information on the controls of hydrogeochemical reactions along respective flow paths as a function of the hydrograph. Home to Apsáalooke/Crow people for generations, the Crow reservation is where the Little Bighorn River (LBHR) incises the landscape serving as the cultural bloodline and source of Apsáalooke livelihood. My initial longitudinal survey analyzing grab samples collected in December 2019 and June 2020 showed that the LBHR watershed is dominated by a Ca/Mg sulfate-bicarbonate solution and contains trace level concentrations of U-238, As-75, and up to 25 PFAS compounds. However, the extent to which pollutants may be stored and transported in association with discharge is unclear. Now, this study seeks to expand by identifying the C-Q relationship in the LBHR to understand the connection between seasonal river flows and pollutant flux. Using in situ multiparameter EXO2 sonde devices, high frequency sample collection, and chemical analyses together will contribute to the understanding of the hydrogeochemical behavior of the LBHR. This investigation will provide C-Q insights, foundation of surface water quality, determine those impacts on tribal water uses, and inform tribal water policy.