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Ripples of Change: Exploring Land Use and Water Health in Lake Sunapee
Ripples of Change: Exploring Land Use and Water Health in Lake Sunapee
Land use changes around Lake Sunapee may seem subtle over time, but their effects on water quality can be significant. My project focuses on how indicators like pH, total phosphorus (TP), and turbidity have fluctuated over the years, giving us insight into how human activities are influencing the lake’s ecosystem. These indicators help highlight connections between development, forest coverage, and water quality in the watershed.
Land Use and Water Quality Indicators
Land Use and Water Quality Indicators
The land cover within the Lake Sunapee watershed hasn’t changed drastically between 2011 and 2021, largely due to the use of coarse resolution data from the MRLC’s National Land Cover Database, which provides data at a 30-meter resolution. This means that while major shifts would be detected, smaller-scale changes, like a few new houses or a small clearing of forested land, might not show up. However, the slight changes that are visible suggest a subtle shift toward more development in some areas, which could lead to increased nutrient runoff and other pollutants entering the lake.
To better understand how water quality has evolved over time in Lake Sunapee, I used a summation method to combine the results from multiple years of interpolation raster's, each representing turbidity, total phosphorus (TP), and pH concentrations in the map below. By adding these raster's together using the Raster Calculator tool, I was able to identify areas where high concentrations consistently occurred across different time periods. This technique highlights 'hotspots' of water quality changes, as the cumulative values show which parts of the lake have been most affected over time.
By displaying the combined raster's side by side, we can clearly observe where the darker colors align, signifying higher concentrations. Turbidity, TP, and pH levels show consistent peaks at their darkest shades around stations 100.1, 30, 70, 10, and 110. Station 70, located closest to Mount Sunapee State Park and Ski Resort, is particularly noteworthy due to the significant seasonal runoff from snowmelt associated with the resort’s activities.
Similarly, Station 30 is positioned near Granliden and Fernwood, as well as the Granliden on Sunapee Golf Course, areas with notable human activity. Station 100.1 is adjacent to Blodgett Landing, which features more shoreline development compared to other parts of the lake. Lastly, stations 10 and 110 are located in coves and near more developed areas such as Georges Mills and Highway 89, which likely contributes to the observed water quality trends in these regions.
Nutrient pollution is one of the primary concerns in watersheds, particularly when it comes to phosphorus. Excessive phosphorus levels can trigger algal blooms, affecting aquatic life and water clarity. Through this project, we analyzed total phosphorus concentrations over time using IDW (Inverse Distance Weighted) interpolation maps. Interestingly, some areas with higher phosphorus levels also aligned with areas of higher turbidity, which suggests that runoff or other inputs may be impacting both water clarity and nutrient levels in tandem.
New Hampshire's lake regions, including Lake Sunapee, benefit from several land-use regulations aimed at protecting water quality. For example, the The Shoreland Water Quality Protection Act (RSA 483-B) establishes a protected shoreland close to public waters, where within this area, vegetation removal, excavation, fill, and development are regulated (New Hampshire Department of Environmental Services. (n.d.)). These protections have helped maintain relatively stable water quality in the lake, but challenges persist, particularly with non-point source pollution, such as stormwater runoff from impervious surfaces.
Local land-use regulations and zoning ordinances also play a role in limiting development in sensitive areas. While these measures aim to balance economic growth with environmental preservation, challenges remain, such as ensuring septic systems are well-maintained to prevent leaching into the lake. Although leaking septic systems were previously a concern for Lake Sunapee, ongoing efforts have helped mitigate this issue.
By looking at the data visualized in this project, including the pH, turbidity, and phosphorus maps, it’s clear that Lake Sunapee is facing both the benefits of strong regulatory oversight and the challenges of subtle land use shifts. While water quality indicators have remained relatively stable, the areas showing higher concentrations of nutrients or decreased water clarity warrant further monitoring. As development continues, even on a small scale, ongoing efforts to manage runoff and pollution sources will be critical in preserving Lake Sunapee's health for years to come.
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