Lake acidification is the lowering of a lake’s pH level, which can be caused naturally or anthropogenically from acidic rain, nitrogen fertilizer run-off, dry deposition of air pollutants ["Freshwater Acidification | Acid Rain | Liming", 2019]. Lake acidification can significantly impact surrounding ecosystems and can cause dramatic changes in the lake’s food web (Schindler et al., 1985). One example of the irreversible stress this placed on aquatic ecosystems is the disappearance of benthic organisms, which are important for nutrient cycling and pollutant and sediment removal, which directly impact water quality (Schindler et al., 1985). Other impacts directly caused by lake acidification include decreased fish reproduction and growth.
Since the 1970s, smelter emissions in Sudbury, Ontario have been reduced by upwards of 90% and re-greening and restoration projects have been launched to rehabilitate the aquatic and terrestrial landscapes. One of these restoration projects targeted a specific catchment of Daisy Lake that included the application of 460 tons of dolomitic limestone, fertilization, seeding of grass and legume species, and planting of Jack pine trees (Gunn et al, 2001). This treatment combined with smelter emission reductions has increased the pH of Daisy Lake to a cicrumneutral 6.89 and allowed the re-establishment of sportfish and sensitive invertebrates (Corston, Gillespie, & Gunn, 2014a; Gunn, Kielstra & Szkokan-Emilson, 2016; Wesolek et al, 2010). As well, the soil has been able to regenerate and promote the growth and colonization of metal- and acid-tolerant tree species, such as white birch and Jack pine (Gunn et al, 2001).
When specifically examining the localized effects of the 1970s catchment reclamation at the corresponding delta and compared across other deltas within Daisy Lake, there is a remarkable improvement to water chemistry and quality, soil accumulation, and vegetative growth (Gunn et al, 2001). This improvement to both the aquatic and terrestrial ecosystem demonstrates the importance and benefits for re-establishing land-water linkages through restoration to promote whole ecosystem recovery (Tanentzap et al. 2014). Although, it is critical to note that the accelerated recovery as a result of catchment reclamation is primarily exhibited through localized effects to the corresponding delta while other deltas continue to recover much more slowly and are a function of catchment features (Kielstra et al, 2017). This highlights the need for future restoration projects targeting other catchments.
Lake acidification and the accumulation of heavy metals are the main concerns of this study area. To determine the most suitable sub-catchment for reclamation, several variables must be considered including but not limited to: water quality, forest cover, and stream flow. Water quality is pertinent to this study because it is a direct measure of the pH, which impacts fish reproduction (Gunn, Kielstra & Szkokan-Emilson, 2016). Vegetation and stream flow is important for adequate fish growth, since terrestrial organic matter is exported by the streams and is needed for aquatic ecosystems to thrive (Tanentzap et al., 2014). However, this data is limited by the fact that the biological data is based on the correlation to measurements of a few unique organisms, in small study areas, which represents a research gap. This data is useful for this project’s study area, but difficult for future projects to apply to different geographical areas that suffer from the same issues. This is due to the difference in terrestrial characteristics which will have a different overall impact on surrounding lakes and streams, similar to comparing land in southern Ontario, Canada versus land in north-western British Columbia, Canada. Future research studies should consider the effects of using biological indicators versus physical indicators to determine the ecological health of a study site.
GIS application to this problem is important for environmental protection and land management in recovery of damaged ecosystems. As stated earlier, air pollutants from mining activity in the Sudbury area has significantly impacted water quality negatively, which can result in lake acidification and accumulation of heavy metals. A GIS will help identify the most suitable area for reclamation, for which the GIS model can then be applied to future study areas with the same objectives.
Purpose of the Research
The purpose of this research is to examine whether water chemistry of each catchment correlates with their characteristics of two lakes in the Sudbury area (the reclaimed Daisy Lake and untreated Baby Lake); upon establishing this connection, a multi-criteria evaluation (MCE) will then be used in ArcMap to determine which sub-catchment is the most suitable one for future treatment based on characteristics of sub-catchment and the current state of associated delta’s recovery.
Objective 1: To determine relevant characteristics of each sub-catchment from literature.
Objective 2: To determine the importance of characteristics and assign relative weights for MCE.
Objective 3: To apply GIS-based MCE to determine the best lake catchment for restoration.
Objective 4: To identify strengths and limitations of the study approach.