New submodel for watershed-scale simulations of fecal bacteria fate and transport at agricultural and pasture lands

Authors: PARK, YONGEUN - Us Forest Service (FS); Pachepsky, Yakov; HONG, EUNMI - Orise Fellow; Shelton, Daniel; WHELAN, GENE - Environmental Protection Agency (EPA)

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 7/7/2016
Publication Date: 7/16/2016
Citation: Park, Y., Pachepsky, Y.A., Hong, E., Shelton, D.R., Whelan, G. 2016. New submodel for watershed-scale simulations of fecal bacteria fate and transport at agricultural and pasture lands. In:ASABE Annual International Meeting, July 17-20, 2016, Oralndo, FL. p.162462856.

Interpretive Summary: Data on microbial fate and transport at the watershed scale are scarce and difficult to collect. This underscores the need to use watershed-scale microbial water quality models that are capable of showing realistic changes in microbial water quality after implementation of best manure and animal waste management practices. Performance of those models depends on accurately mimicking the major fate and transport processes. As the experimental information about those processes accumulates, improvements can be made. We have included the latest data on E. coli fate and transport in the module compatible with major watershed-scale water quality models. This work presents the test of this module with data from four years of experiments with release and removal of E. coli from manure at field scale during and after sequential irrigation events. The module performed satisfactorily. Results of this work can be used by industry, consultants and researchers to advance diagnostics, monitoring, predictions, and management of microbial impairment of surface fresh water sources.

Technical Abstract: Microbial contamination of waters is the critical public health issue. The watershed-scale process-based modeling of bacteria fate and transport (F&T) has been proven to serve as the useful tool for predicting microbial water quality and evaluating management practices. The objective of this work is to review recent data on and models of processes controlling the fecal indicator bacteria (FIB) fate and transport (F&T), and to incorporate these new findings in a submodel that could be included in watershed-scale water quality models. The reviewed specific bacteria F&T processes include aboveground survival, survival in soil, distribution between suspended and sediment-associated in runoff bacteria fractions, rainfall-induced wash-off after animal waste deposition, mobilization from soil to runoff, and distribution between runoff and infiltration. Watershed models provide essential inputs for the bacteria F&T submodel including manure and animal waste loads, manure and animal waste erosion rates, incorporation scheduling, runoff and infiltration rates, sediment transport, retention in vegetated buffer strips, and soil and air temperature time series. We used independent drivers to evaluate and parameterize the model representation of processes in manure, animal waste, soil and water in the submodels. Decision trees and Arrhenius-type Q10 models were applied to simulate bacteria population dynamics as dependent on major survival factors. Simulations showed a reasonable prediction of FIB F&T when compared with the data of four years experiments with bacteria release from irrigated manured fields in Beltsville MD. The submodel is added to APEX and SWAT watershed-scale models and results of performance evaluation will be presented.