Submitted to: Human and Ecological Risk Assessment
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/4/2013
Publication Date: 2/6/2014
Publication URL: http://handle.nal.usda.gov/10113/58694
Citation: Jayakody, P., Parajuli, P.B., Brooks, J.P. 2014. Evaluating spatial and temporal variability of fecal coliform bacteria loads at Pelahatchie Watershed in Mississippi. Human and Ecological Risk Assessment. 20:1023-1041. Interpretive Summary: Water fouling by nutrients and pathogens are problems for water treatment systems and overall for water availability, thus increasing costs associated with potable water. The Pelahatchie watershed, located in Mississippi, is a watershed impacted by many sources of these pollutants, including wildlife, agricultural operations, and failing septic systems. Collecting and processing water samples can be a costly and laborious process, whereby intensive sampling of every watershed is nearly impossible. However, modeling enables decision makers to estimate the presence of pathogens (or pathogen bacterial indicators) and nutrients in surface water sources, without the need for collecting many samples. Data can be collected from nearby pathogen or nutrient sources, which can then be modeled to estimate the bacterial load in the water source. In this study, data was collected from a number of sources, analyzed, and modeled using a currently available transport model to estimate the bacterial load in the Pelahatchie watershed. This study demonstrated that watershed landscape areas with higher elevation, population density, and grazing lands contributed more bacterial loads to the nearest streams using these modeling approaches. This study should help watershed managers implement best management practices to improve water quality.
Technical Abstract: Bacterial contaminations of surface waters are an increasing concern for scientists because pathogenic bacteria can cause adverse effects on human health. This research was performed to investigate spatial and seasonal variability of fecal coliform bacteria (FCB) concentrations from the Pelahatchie watershed (527 km2) in Mississippi. Livestock manure, poultry litter, and effluent from the failing septic systems were identified as major sources of FCB from the Pelahatchie watershed. The Soil and Water Assessment Tool (SWAT)/microbial sub-model was applied, and model predicted FCB concentrations were compared with the monthly measured FCB concentrations (2000-2008) at the outlet of the watershed. New methodologies were introduced to incorporate bacteria loads into the bacteria model. Results showed coefficients of determination (R2) of 0.71 to 0.75, and Nash-Sutcliffe efficiency index (NSE) of 0.67 to 0.75 during bacteria model calibration and validation periods respectively. Seasonal analysis of the model simulated results determined the highest bacteria concentrations in January, whereas the lowest concentrations predicted in June. Watershed landscape areas with higher elevation, population density, and grazing lands contribute more bacteria loads to the nearest streams. This study helps watershed managers to implement best management practices to improve water quality.