RELATIVE RAIN AND GROUNDWATER CONTRIBUTIONS TO STREAMFLOW ACROSS TWO FLOW REGIMES IN NORTHERN ARKANSAS
Stream water sources play a key role in nutrient and water budgets. The relative amounts of precipitation and groundwater that comprise channel flow represent an important difference in the two dominant flow regimes in northern Arkansas, Runoff Flashy and Groundwater Flashy streams. However, groundwater contribution data in hydrologic models were generated using catchment-level density of springs as well as base flow and groundwater recharge indices at 1-kilometer scales. Direct measures of water chemistry of streams, groundwater, and precipitation would better estimate water sources in small headwater systems. We sampled three Groundwater and three Runoff streams from March to October 2018 and used end-member mixing analysis to apportion streamflow sources. While one Runoff stream was consistently precipitation-driven, all other systems exhibited temporal variation in dominant flow sources. Across Groundwater streams, groundwater contributions ranged from 42-44% (5th percentile), 80-82% (50th percentile), and 95-97% (95th percentile) of channel flow. In Runoff streams, mixing analysis revealed runoff contributions to be 33-81% (5th percentile), 79-91% (50th percentile), and 97-100% (95th percentile) of discharge. We compare our results to published flow source predictions and present a percentile-based approach for refining flow regime classifications in northern Arkansas.
Allyn Dodd (Primary Presenter/Author), Lyon College, firstname.lastname@example.org;
Erik Pollock (Co-Presenter/Co-Author), University of Arkansas, email@example.com;
Samuel Dias (Co-Presenter/Co-Author), University of Arkansas, firstname.lastname@example.org;
Brianna Hillebrand (Co-Presenter/Co-Author), University of Arkansas, email@example.com;
Michelle Evans-White (Co-Presenter/Co-Author), University of Arkansas, firstname.lastname@example.org;