The purpose of this study was to identify vulnerability to groundwater contamination and areas most suitable for green space conversion within the Grand River Watershed. The DRASTIC model was comprised of seven hydrogeological parameters which when combined and analyzed, output a final vulnerability map. The final vulnerability map was reclassified to identify the top ten percent most vulnerable areas to groundwater contamination within the Grand River Watershed. The MCE model included one constraint (the DRASTIC model output) and five environmental/social parameters, which when combined and analyzed, output a final suitability map. The highest suitability values were extracted from the final suitability map using the reclassify tool to produce the three best sites for green space conversion within the Grand River Watershed.
DRASTIC Model Findings
The DRASTIC results produced a raster with scores that range from 50 - 209 (Figure 8 in Appendix B), then using Equation 2, standardized onto a 0-100 scale as displayed in Figure 4. These areas of very high vulnerability seem to concentrate around the central part of the watershed. It is important to note that areas of intermediate vulnerability are not free from contamination but are much less susceptible to groundwater contamination.
The area of focus is to identify the most vulnerable areas within the Grand River Watershed. Isolating the top 10 percent of areas with the highest vulnerability rating effectively narrows down the results to a subset of highly vulnerable areas (Figure 5). This layer will be analyzed in the MCE process to identify the most suitable places for a green space. Having too many vulnerable areas to choose from can be problematic because the Grand RIver Watershed is very large.
Figure 4: DRASTIC Model Output
Figure 5: Final Vulnerability Map
MCE Model Findings
The MCE model used for the suitability assessment derived an output of low to high suitability for green space conversion within the Grand River Watershed. The output of this suitability assessment is based on the identified constraint and criteria, including the DRASTIC model output, and distance from water, forest, residential areas, recreational areas, and arterial roadways respectively. As a constraint, the DRASTIC model output effectively restricted areas of high suitability to areas of high groundwater contamination vulnerability. Areas of high suitability for green space conversion within the Grand River Watershed are identified as areas in close proximity to water, forest, residential areas, recreational areas and roads. High-suitability areas are found most dominantly surrounding major cities, and centrally located within the Grand River Watershed (See Figure 6 in Appendix B).
The final suitability map and green space sites were a result of all hydrogeological factors and green space implementation suitability factors. Such factors include: depth to groundwater, net recharge, aquifer media, soil media, topography, impact of vadose zone, hydraulic conductivity, and distance from water, forest, residential areas, recreational areas, and roads. Ultimately, the greatest score for final suitability of green space site implementation was 89.3. The reclassification tool was used to extract all sites with the score 89.3. From this function, the three sites indicated as the most suitable for green space conversion were identified. As predicted, the three sites indicated as the most suitable for green space conversion were located on agricultural land. This prediction was based on the idea that landscapes dominated by agriculture have high permeability in terms of the surface, and large amounts of anthropogenic inputs. Additionally, the three sites indicated as the most suitable for green space conversion were located along the Grand River (the major water source within the Grand River Watershed), and in close proximity to forest, residential areas, recreational areas, and roadways (Figure 8).
Figure 6: MCE Model Output
Figure 7: Final Suitability Map
Overall Research Findings
Figure 8: Best Sites for Green Space Implementation within the Grand River Watershed