SIMULATING SURFACE AND GROUND WATER FLUXES IN COMPLEX KARST SYSTEMS – ANALYSIS OF MIDDLE AND EAST TENNESSEE’S SEQUATCHIE VALLEY USING THE ANNAGNPS WATERSHED POLLUTANT LOADING MODEL

Abstract

Topographic feature evaluation is a critical component for accurate interpretation and quantification of hydrologic flow in watersheds. In a typical drainage basin, topographic features identify and define surface drainage paths as flow traditionally travels through the most direct pathway. Alternatively, hydrology in karst terrain is often heterogeneous to surface topography and water rapidly redirects underground only to emerge elsewhere as discharge. This study evaluated the predictability of the Annualized Agricultural Non–Point Source (AnnAGNPS) model to simulate runoff over a six–year period (2016 to 2021) in the Sequatchie Valley and adjacent karst valleys located in the Cumberland Plateau of Middle and East Tennessee. After runoff calibration and statistical analysis, it was determined that utilizing the automated/semi–automated processes of AnnAGNPS produced results that indicate the model to be appropriate in simulating surface and surface–ground flow at annual–scales, although future work is recommended to improve monthly–scale results.