Abstract
Watershed vulnerability and the characterization of potential risk are important inputs for decision support tools in assessing watershed health. Most previous studies have focused on the assessment of the environmental risk using physicochemical properties of surface water and mathematical models to predict the health of a watershed. Here, we present a new methodology for evaluating watershed vulnerability using the analytic hierarchy process (AHP) and weighted overlay analysis. The new methodology provides an inexpensive approach for assessing areas that need more investigation based on known factors such hydrogeological, geological, and climate parameters without the need for site-specific physicochemical data. The proposed method was implemented using six main factors that influence water quality: land use, soil type, precipitation, slope, depth to groundwater, and bedrock type. Vulnerability was predicted for ten sub-watersheds within the Eagle Creek Watershed in Indiana using publicly available data input into geographic information system. Combination of watershed susceptibility assessment and GIS spatial analysis tools was used to produce the maps that show the susceptible zones within a watershed. A comparison of the resulting vulnerability estimates showed the expected significant positive correlations with measurements of nitrate, phosphate, temperature, and electrical conductivity. Likewise, the vulnerability estimates negatively correlated with dissolved oxygen and E. coli. Furthermore, the validation of the proposed approach revealed that the areas predicted to have high vulnerability did have lower water quality indices; the results showed a high negative correlation (r2 = 0.77, p < 0.05) between water quality index (WQI) and vulnerability which strongly suggests this method can be used successfully to assess a watershed’s susceptibility.
Highlights
Water quality degradation from multiple sources of contamination has become a critical global issue (USEPA 2016; FAO 2017)
The watershed susceptibility assessment method uses some features that have been weighted based on their contribution in surface water contamination and calculates a vulnerability index value for the area under consideration
We identified the primary parameters affecting watershed vulnerability and suggested new weighting factors for each parameter using analytic hierarchy process (AHP) analysis
Summary
Water quality degradation from multiple sources of contamination has become a critical global issue (USEPA 2016; FAO 2017). Quantifying the vulnerability of watersheds to NPS pollution is important for recognizing which watersheds are most at risk of impairment and determining where changes in land use/land cover (LULC) might improve water quality conditions (USEPA 2008). The use of an appropriate model for watershed assessment that includes the variables listed above and can be modified as these variables change could be essential for evaluating continuous spatial and temporal distribution variations in watershed information. Some of these models are discussed in the following paragraph
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