Predicting Rural Land Use/Land Cover Change to Support Groundwater Contamination Risk Assessment

Abstract:

The quality of groundwater supply in many rural regions is impacted by agricultural activities, including nutrient application. The physiographic attributes of a region, which control intrinsic groundwater vulnerability, are commonly combined with land use data as a proxy for pollutant loading to qualitatively determine groundwater contamination risk (via methods such as DRASTIC). Changes in future climate/groundwater recharge and land use/land cover have the potential to alter spatial patterns in contamination risk. However, of these variables, changes in land use/land cover are less frequently incorporated in future risk assessments and hydrologic modelling studies. Complex socio-economic considerations, lack of a standardized methodology, and uncertainty in the selection of land cover datasets are challenges impeding such investigations. This study examines future land use/land cover predictions within the Upper Parkhill watershed, an agricultural headwater catchment in southwestern Ontario, Canada. The TerrSet Land Change Modeler (Clark Labs) was used to analyze past land use/land cover change, model the potential for land transitions, and predict mid-century (2050) conditions. Several important transitions were detected in the analysis of historical land use maps including a combination of cropland expansion, reforestation, and settlement growth which were found to be driven largely by proximity to each existing land base. These transitions were projected into the future for incorporation in a groundwater contamination risk assessment. However, by mid-century, only approximately 3% of the watershed area was predicted to undergo land conversion (since the year 2000). This relatively small amount of change suggests that comprehensive future land change simulations may not be necessary in certain rural regions, depending on municipal planning constraints, population growth scenarios, and study objectives. These findings provide important insight for the development of future hydrologic investigations.