A conceptual framework for groundwater/surface-water interactions and identifying potential impacts on water quality, water quantity and ecosystems

Abstract

Groundwater/surface-water (GW/SW) interactions play an important role in controlling the physical, chemical and biological integrity of surface water and groundwater systems in the Great Lakes Basin (GLB). Increased recognition of their importance is illustrated by the addition of Annex 8 on groundwater to the Great Lakes Water Quality Agreement in 2012. GW/SW interactions in the GLB are complex can impact water quantity, water quality and ecosystem health of streams and lakes including the Great Lakes. Although considerable work has been done to characterize the geology, hydrology, and groundwater resources in Southern Ontario, there are still numerous science gaps with respect to GW/SW processes and no guidance or framework exists for evaluating the importance of GW/SW interactions. Decisions regarding land use and resource development are often made without an adequate understanding of the way in which GW/SW interactions may impact water quantity, water quality and ecosystem health. Therefore, to enhance the ability to make informed science-based decisions, a conceptual framework has been developed to help evaluate GW/SW interactions and identify potential impacts. The purpose of the framework is to provide a comprehensive and logical approach to understanding, evaluating, and identifying the important factors and processes that control GW/SW interactions of both streams and lakes and linking them to impacts on their water quantity, water quality, and ecosystems. The framework consists of five fundamental parts including: 1) the surface water system; 2) the groundwater system; 3) the interface connectivity; 4) GW/SW interactions; and 5) the ultimate impacts on the water quantity, quality and ecosystems associated with the surface water, groundwater and the transition zone. For each of the first four parts, lists of important factors and critical processes have been identified. For ease of use, the framework is presented as a flow chart that highlights the relationship between factors and processes and the potential impacts on the surface water, groundwater, and the transition zone. Processes that are common to both streams and lakes are identified as well as those processes unique to each. A benefit of the framework is that it is flexible and can be adapted to the needs of the end-user to develop scientifically sound understanding of a setting and to help answer key management questions. This flexibility is important in Southern Ontario because there is a range of hydrological landscape settings where the mechanisms controlling GW/SW interactions and resulting impacts are vastly different. To illustrate the application of the framework, case studies will be presented for different GW/SW interaction settings (i.e., riverine and nearshore lake settings) and management questions. The framework presented provides a comprehensive and accessible approach to evaluating GW/SW issues in Southern Ontario.