Modeling the transport of sucralose, an anthropogenic tracer, in an effluent dependent watershed with the Soil and Water Assessment Tool during an extreme drought.

Contaminants of emerging concern (CECs) in rapidly urbanizing watersheds represent an area of increasing attention. The Soil and Water Assessment Tool (SWAT), has been used for numerous water quality and quantity assessments, but CEC studies using SWAT are limited. Because the North Bosque watershed represents an ideal system to study historical and emerging water quality questions, I examined the capacity of SWAT to potentially model CECs using sucralose during an extreme drought, when the in-stream flows downstream from Stephenville, Texas, USA were dependent on effluent discharge. Modeling outputs throughout the watershed were compared to field observations of CECs (quantified by isotope dilution LC-MSMS) in surface water. Sucralose, an ideal effluent tracer, simulation outputs were similar at wastewater treatment plants but in-stream concentrations were lower than predicted potentially due to transport from surface water to groundwater, which is not accounted for by SWAT. This suggests that CECs may be entering the Trinity aquifer in a primary recharge area.