LAKE WARREN WATERSHED MANAGEMENT PLAN PREPARED FOR: PREPARED BY: Southwest Region Planning Commission FB Environmental Associates 37 Ashuelot Street 170 West Road, Suite 6 Keene, NH 03431 Portsmouth, NH 03801 www.swrpc.org www.fbenvironmental.com LAKE WARREN WATERSHED MANAGEMENT PLAN Lake Warren Watershed Data Source: NH GRAN!T, FBE Projection: NA D 7983 State Plane Cheshire County New Hampshire New Hampshire FIPS 2800 N Created by: FBE, September 2076 0••••••• 0.25 0.5======::J Miles A LEGEND c::::l Lake Warren Watershed c:::~. Town M Lake/ Pond G3 Wetland ~ Stream ~ Road Nh Route 123 "5 0 Vl" NH i LAKE WARREN WATERSHED MANAGEMENT PLAN Lake Warren Watershed Management Plan Prepared by FB Environmental Associates in cooperation with the Southwest Region Planning Commission, the Lake Warren Association, the Lake Warren Watershed Steering Committee, and the New Hampshire Department of Environmental Services. December 2016 CONTACT Southwest Region Planning Commission 37 Ashuelot Street Keene, NH 03431 (603) 357-0557 http://swrpc.org/ Funding for this project was provided in part by a Watershed Assistance Grant from the NH Department of Environmental Services with Clean Water Act Section 319 funds from the U.S. Environmental Protection Agency. ii LAKE WARREN WATERSHED MANAGEMENT PLAN EXECUTIVE SUMMARY Located in southwestern New Hampshire, Lake Warren has been an important natural resource in the Town of Alstead for over 200 years. As the headwaters of Warren Brook, the lake was initially dammed to provide a source The Lake Warren Watershed Management Plan of water to downstream mills. With time, the lake has also is a scientifically-based plan that become a highly valued recreational resource to both provides decision makers and residents and visitors who enjoy its scenic beauty and residents the tools needed to calm, quiet character. The lake also provides critical protect the water quality of the habitat for a diverse abundance of plants, wildlife, and lake for future generations. aquatic life. The water quality of lakes and streams can decline rapidly because of stormwater runoff from watershed development (including roads, agriculture, and residences). Taking proactive steps to properly manage and treat stormwater runoff to protect these important water resources is essential for continued ecosystem health, including resources valued by humans. The Lake Warren Watershed Management Plan is the culmination of several years of effort by the many individuals who care about the long-term protection of water quality in the lake. The Lake Warren Association (LWA) was formed in 1985 with the goal of protecting the lake. By partnering with the Southwest Region Planning Commission (SWRPC), the New Hampshire Department of Environmental Services (NHDES) awarded the group both a Water Quality Planning Grant (Section 604 (b) of the Clean Water Act) and a Watershed Assistance Grant for implementation (Section 319 of the Clean Water Act) with funds from the United States Environmental Protection Agency (USEPA). Stakeholders from the local to state level have collaborated on this effort, including the Town of Alstead, New Hampshire Fish and Game Department (NHFGD), the Soak Up the Rain program, the Cold River Local Advisory Committee (CRLAC), and numerous watershed residents. iii LAKE WARREN WATERSHED MANAGEMENT PLAN The Lake Warren Watershed The Lake Warren watershed covers approximately 4.9 square miles (3,111 acres) in southwestern New Hampshire, and is entirely within the Town of Alstead. The lake itself is 0.3 square miles (195 acres), surrounded by moderate to steep hills. The watershed is mostly forested and is home to a diverse community of fish, birds, mammals, and plants that are dependent on clean water for survival. Based on available data from NH GRANIT, conservation land around Lake Warren covers approximately 8% (234 acres) of the watershed. The surrounding landscape includes 42 acres of open waters and wetlands and more than 13 miles of mapped streams. Major tributaries to the lake include Smith Hill Brook, Hale (Carmen Cove) Brook, and the Spruce River, among others in the watershed. These tributaries and the contributing land cover of their watersheds are important to the water quality of Lake Warren. Why Develop a Watershed Management Plan? Lake Warren is currently listed as impaired for Aquatic Life Use (ALU) due to high levels of Chlorophyll-a (Chl-a) and total phosphorus (TP), and low pH. Excess TP can stimulate algae growth, which typically results in a decrease in Secchi disk transparency (i.e., a decrease in water clarity) due to the additional algae. This relationship between nutrients, algae, and transparency holds true in Lake Warren, where TP and Chl-a have increased since 1980 while Secchi disk transparency has decreased. Due to the relationship between phosphorus and algae (Chl-a), as well as the potential for unmitigated sources of pollution (i.e., phosphorus) from watershed development in the coming years, phosphorus is the focus of this management plan. The Steering Committee has set interim water quality goals that would reduce current median in-lake total phosphorus by 25% (44.4 kg/year) to 8.3 ppb in Lake Warren. Achieving these goals will help reduce current in-lake phosphorus and Chl-a over time and help safeguard against increased phosphorus loading from the landscape as a result of development (e.g., septic systems, paved surfaces, sediment, etc.). The ultimate goal is to improve the water quality to the point that the lake is no longer impaired. This comprehensive watershed plan provides a roadmap for preserving the water quality of Lake Warren, and provides a mechanism for procuring funding (i.e., Section 319 grants) to secure action needed to achieve water quality goals. USEPA requires that a Watershed Management Plan be created for communities to be eligible for watershed assistance implementation grants. In addition, this plan sets the stage for ongoing dialogue among key stakeholders in many facets of the community, and promotes coordinated action to address future development in the watershed. The success of this plan is dependent on the continued concerted effort of volunteers, and a strong and diverse Steering Committee that meets regularly to review progress and make any necessary adjustments to the plan. iv LAKE WARREN WATERSHED MANAGEMENT PLAN As part of the development of this plan, water quality and assimilative capacity analyses and watershed and septic surveys were completed in 2013-2014. Results of these efforts were used to run a land-use model, or Lake Loading Response Model (LLRM), that estimated the current and historical amount of phosphorus being delivered to the lake from the watershed. An additional analysis of water quality data conducted by CRLAC (referenced in the 2012 Lake Warren Comprehensive Lake Inventory and Management Plan) was also consulted in drafting the Watershed Management Plan. The Steering Committee and other volunteers provided vital on-the-ground support and technical review throughout the process. Plan Components The Lake Warren Watershed Management Plan includes nine key planning elements to address nonpoint source (NPS) pollution (Section 1.3). These guidelines, set forth by the USEPA, highlight important steps in protecting water quality for waterbodies impacted by human activities, including specific recommendations for guiding future development, and strategies for reducing the cumulative impacts of NPS pollution on lake water quality. Below is a summary of information presented by Section: SECTION 1– INTRODUCTION Section 1 introduces the plan by describing the problem, the goals and objectives, the community-based planning process, and applicable federal regulations. Section 1 also provides background information, including watershed survey results and current watershed efforts in phosphorus reduction and awareness. SECTION 2– WATERSHED CHARACTERIZATION Section 2 describes the watershed, providing detailed information about climate, population and demographics, land cover, topography, soils and geology, wetlands and riparian habitat, lake morphology and morphometry, and drainage areas or tributaries. SECTION 3– ASSESSMENT OF WATER QUALITY Section 3 describes water quality standards, highlights the estimated sources of phosphorus to Lake Warren, and provides a summary of current classification based on the water chemistry assessment and water quality goals. Identification of nonpoint source pollution is also included in this section. SECTION 4– MANAGEMENT STRATEGIES Section 4 outlines the necessary management strategies (both structural and non-structural BMPs) to reduce phosphorus inputs to Lake Warren. Current and future sources of phosphorus are discussed and an adaptive management strategy is presented. v LAKE WARREN WATERSHED MANAGEMENT PLAN SECTION 5– PLAN IMPLEMENTATION Section 5 describes who will be carrying out this plan and how the action items will be tracked to ensure that necessary steps are being taken to protect and improve the water quality of Lake Warren over the next ten years. This section also provides estimated costs and technical assistance needed to successfully implement the plan and a description of the evaluation plan to assess the effectiveness of restoration and monitoring activities. Funding the Plan Reducing phosphorus inputs from existing and future development in the Lake Warren watershed will require significant financial and technical resources on the order of $386,000 over the next ten years, including the financial