Introduction

Literature Review

Located in the south-west side of New Hampshire, Lake Sunapee comprises 4,155 acres with a maximum depth of 112 ft (Lake Sunapee Protective Association et al., 2020). The Lake Sunapee Watershed in which Lake Sunapee is located is dominated by forests, wetlands, ponds, and tributaries, including 13 named lakes (Lake Sunapee Protective Association et al., 2020). The lake’s watershed encompasses 29,832 acres and includes portions of 6 small towns: Newbury, Springfield, Sunapee, New London, Sutton and Goshen (Lake Sunapee Protective Association et al., 2020). The town with the largest population in the Lake Sunapee Watershed is New London with about 4,402 people as of 2020 (U.S. Census Bureau, 2014). While the water quality of Lake Sunapee has been generally good with relatively low nutrient levels, some parts of Lake Sunapee and other lakes and ponds in the watershed are showing increases in nutrients like phosphorous (Lake Sunapee Protective Association et al., 2020). Anthropogenic activities, particularly those related to land use—such as residential housing development, road maintenance, commercial expansion, and the development or redevelopment of lakefront properties—are likely contributing factors to the increased phosphorus levels in the watershed (Lake Sunapee Protective Association et al., 2020). 

The Lake Sunapee Protective Association (LSPA) is the oldest environmental organization in New Hampshire and is a site member of the Global Lake Ecological Observatory Network (GLEON) which monitors lake health around the world (Lake Sunapee Protective Association, 2022, 0:07:50). The water quality data collected for the LSPA and New Hampshire Department of Environmental Services (NHDES) is accomplished in large due to the expansive volunteer citizen science organization; Volunteer Lake Assessment Program (VLAP). These volunteers operate under an EPA-approved Quality Assurance Project Plan (QAPP) which ensures high-quality data is being collected at the 180 lakes being monitored throughout New Hampshire (Lake Sunapee Protective Association (LSPA) (n.d.c)). In addition, in 2007 the LSPA deployed a buoy which records air and water data every ten minutes all year and has been included in dozens of international lake studies (Lake Sunapee Protective Association (LSPA) (n.d.a)). 

Water quality on lakes is a delicate balance of biological and physio-chemical parameters and is often measured based on heavy metals, eutrophication potential, and other indices (Vasistha & Ganguly, 2018). The LSPA has been monitoring pH, specific conductivity or specific conductance, dissolved oxygen, Chlorophyll-a, total phosphorous, turbidity, alkalinity, apparent color, Chloride, E. coli, and transparency to evaluate long term trends over time (Lake Sunapee Protective Association (LSPA) (n.d.b)). Determining what might be influencing a change in a water quality parameter is complex but extremely important for maintaining healthy waters. Water quality degradation has been attributed to many factors such as climate change, vegetation cover, river topography, and land use in catchment areas (Cheng et al., 2022). There have been many studies assessing the relationship between land use and water quality. It has been estimated that in the last sixty years, land use change has affected nearly a third of the global land area and about three-quarters of the total land surface has been altered by humans (Winkler et al., 2021). This is relevant because several studies have reported that urban and agricultural land have a statistically significant and consistently negative association with water quality (Locke, 2024). For example, increased impervious surfaces (like in cities) have been linked to water quality impairment, while natural vegetation (like forests) has been positively correlated with improved water quality by filtering pollutants (Locke, 2024). Specifically, some studies found that total phosphorous increased with a high percentage of cropland.  

When evaluating land use and its impact on water quality, it’s important to evaluate how a water body’s overall heath responds to certain land-use driven factors like phosphorous, pH, and turbidity. In fresh water like lakes, phosphorous is usually the nutrient limiting primary production, and increased phosphorous has been linked to a high percentage of cropland (Jordan et al., 2018). However, it’s important to note that water quality is complex, and it is unlikely that just one factor will influence the overall water quality of a lake, but instead is a cumulation of many factors. On a broad scale, some of these factors include, but are not limited to, hydrology, soil properties, topography, seasonality and historical land use or its spatial distribution in the catchment (Ramião et al., 2020).