A GIS Multi-Criteria Analysis Tool for a Low-Cost, Preliminary Evaluation of Wetland Effectiveness for Nutrient Buffering at Watershed Scale: The Case Study of Grand River, Ontario, Canada

Abstract

One significant concern of Ontario’s water quality management is the reduction in nutrient export. Decision makers have considered nature-based solutions, such as wetlands, depending on their cost-effectiveness for nutrient filtering. All wetland ecosystems interact with the surrounding environment; however, their performances are not always known, which prevents a fair comparison with other treatment alternatives. This study presents a methodological approach for mapping areas that can potentially support effective (or ineffective) wetlands for nutrient buffering. The Grand River watershed, Ontario was selected to demonstrate the methodology. Geographic Information Systems (GIS) are combined with multi-criteria analysis (MCA) to evaluate wetland effectiveness under geomorphological, climatological, hydrological, and land use factors. The selected factor maps (criteria) are normalized, and then used as inputs in an analytical hierarchy process (AHP) and weighted by experts based on how these factors affect wetlands’ performance. The promising areas’ spatial distributions are the output, which is compared with previous studies’ mappings of nutrient concentrations in the watershed. The proposed tool provides a low-cost preliminary estimation that informs policymakers if wetland solutions could achieve the desired environmental goals. This methodological approach supports Canadian wetland conservation efforts and enables a more complete decision-making process.