Submitted to: Environmental Modelling & Software
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2017
Publication Date: N/A
Citation: N/A Interpretive Summary: Sources of fecal wastes such as septic systems and livestock farms can release pathogens into the environment. Rainfall or snowmelt can transport these pathogens over the land surface and into streams and rivers where people could be exposed to contaminated water and become sick. There are models that can describe this pathogen movement, but many do not account for the quantity of fecal wastes and pathogens on the land surface at the beginning of the transport process. This study developed the calculations for determining the number of pathogens reaching the land surface from several sources: manure applied to farm fields, pastured livestock directly defecating on farmland, urban areas, and point sources such as wastewater treatment plants. The calculations are programmed into software that is readily compatible with the other transport models. This tool will give land and water managers the capability to quickly assess the sources and amounts of pathogens reaching surface waters, and with this knowledge minimize people’s exposure to contaminated water.
Technical Abstract: Many watershed models simulate overland and instream microbial fate and transport, but few provide loading rates on land surfaces and point sources to the waterbody network. This paper describes the underlying equations for microbial loading rates associated with 1) land-applied manure on undeveloped areas from domestic animals; 2) direct shedding (excretion) on undeveloped lands by domestic animals and wildlife; 3) urban or engineered areas; and 4) point sources that directly discharge to streams from septic systems and shedding by domestic animals. A microbial source module, which houses these formulations, is part of a workflow containing multiple models and databases that form a loosely configured modeling infrastructure which supports watershed-scale microbial source-to-receptor modeling by focusing on animal- and human-impacted catchments. A hypothetical application – accessing, retrieving, and using real-world data – demonstrates how the infrastructure can automate many of the manual steps associated with a standard watershed assessment, culminating in calibrated flow and microbial densities at the watershed’s pour point.