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Like many waterbodies throughout New Jersey, some of the lakes within Mercer County Park have been increasingly affected by harmful algal blooms (HABs) in recent years. In response to the growing frequency, duration, and severity of these blooms, the Mercer County Park Commission (MCPC) has intensified its efforts to enhance the overall health of its lakes. To address these challenges, the County of Mercer tasked the MCPC with developing a comprehensive Lake and Watershed Management Plan. The ultimate goal is to ensure the health, stability, and sustainability of the park's aquatic ecosystems, thereby enhancing the recreational experience for park users. In this endeavor, the MCPC has partnered with Princeton Hydro to bridge gaps in the existing data and create a thorough management plan. The plan documents the current conditions of waterbodies within the park, including Mercer Lake, which is the largest, and its surrounding watershed; identifies and prioritizes existing and potential water quality challenges; and provides targeted recommendations for treatment and restoration. Princeton Hydro conducted a detailed analysis of the lakes' ecological health, including water quality monitoring, bathymetric mapping, and assessment of hydrologic and pollutant budgets. These comprehensive efforts have culminated in a robust management plan designed to protect and improve the lakes' ecological balance and recreational value. Expanding the Initiative Across Mercer County While Mercer Lake is a key focus, Princeton Hydro's commitment extends beyond this single waterbody. Recognizing the interconnected nature of the county's aquatic ecosystems, the team conducted similar analysis and developed Lake and Watershed Management Plans for three additional lakes in other parks within Mercer County. These lakes are:
Mercer County Park, spanning over 2,500 acres across the Townships of West Windsor, Hamilton, and Lawrence, is a treasured natural resource. Like many waterbodies throughout New Jersey, some of the lakes within Mercer County Park have been increasingly affected by harmful algal blooms (HABs) in recent years. In response to the growing frequency, duration, and severity of these blooms, the Mercer County Park Commission (MCPC) has intensified its efforts to enhance the overall health of its lakes.
To address these challenges, the County of Mercer tasked the MCPC with developing a comprehensive Lake and Watershed Management Plan. The ultimate goal is to ensure the health, stability, and sustainability of the park's aquatic ecosystems, thereby enhancing the recreational experience for park users. In this endeavor, the MCPC has partnered with Princeton Hydro to bridge gaps in the existing data and create a thorough management plan.
The plan documents the current conditions of waterbodies within the park, including Mercer Lake, which is the largest, and its surrounding watershed; identifies and prioritizes existing and potential water quality challenges; and provides targeted recommendations for treatment and restoration.
Princeton Hydro conducted a detailed analysis of the lakes' ecological health, including water quality monitoring, bathymetric mapping, and assessment of hydrologic and pollutant budgets. These comprehensive efforts have culminated in a robust management plan designed to protect and improve the lakes' ecological balance and recreational value.
While Mercer Lake is a key focus, Princeton Hydro's commitment extends beyond this single waterbody. Recognizing the interconnected nature of the county's aquatic ecosystems, the team conducted similar analysis and developed Lake and Watershed Management Plans for three additional lakes in other parks within Mercer County.
Each of these lakes, like Mercer Lake, faces unique challenges related to maintaining water quality, protecting ecological balance, and mitigating HABs. By applying a comprehensive approach tailored to the specific conditions and needs of each lake, Princeton Hydro aims to enhance the overall health of these vital resources.
Let's dive into the details of Mercer Lake's plan!
The first crucial step in developing Mercer County Park's comprehensive lake management plan involved a thorough review of historical data obtained from various sources, including the County, New Jersey Department of Environmental Protection (NJDEP), New Jersey Department of Transportation (NJDOT), and U.S. Geological Survey (USGS). This review was essential for capitalizing on established water quality trends, identifying recurring problems, and evaluating the success of previous restoration efforts.
The historical data review spanned an impressive range of years from 1963 to 2016, though it did contain some significant gaps. Despite these gaps, the long-term data provided invaluable insights into the lake's ecological history. By integrating reliable data from past studies, the team could complement their field efforts with supplemental information.
Princeton Hydro examined data on Mercer Lake, a key focus of the management plan initiative, and on all streams within each watershed that feed into the lake. This included any available surface water data from the USGS, a standard approach in aquatic system studies. By analyzing these data, the team identified trends in water quality, highlighted persistent issues, and assessed the effectiveness of past restoration efforts.
This comprehensive historical data review set the stage for a robust watershed assessment, ensuring that the management plan would be informed by a solid foundation of past knowledge.
A bathymetric survey is a scientific method used to map the depths and topography of waterbodies, providing detailed information about the underwater terrain and the distribution of sediments. This survey is crucial for understanding various aspects of a lake's ecosystem, including sediment thickness, water volume, and potential areas for dredging. The data gathered from a bathymetric survey helps in making informed decisions regarding the restoration and protection of lakes.
Princeton Hydro conducted the bathymetric survey using a calibrated sounding rod for shallow areas and a dual-frequency echo sounder with GPS for deeper regions. The sounding rod was employed in areas with water depths of 12 inches or less and where sediment composition hindered echo sounding. The echo sounder, a Knudsen Engineering model 1612, used high and low frequencies to distinguish the top and bottom of sediment layers. Data points were collected along predetermined transects spaced 150 feet apart, running from shoreline to shoreline in a north-south direction.
Once fieldwork was completed, the collected data was processed using Hypack Max software. This involved editing the raw sounder data to correct errors such as double reflections and interference from aquatic vegetation. The cleaned data was exported to ArcGIS for further analysis and mapping.
The results of the bathymetric survey revealed that Mercer Lake, a key focus of the lake management plan, covers a surface area of approximately 287 acres and is primarily an oval-shaped impoundment. The lake receives inflow from Assunpink Creek and its tributaries and discharges water westward, eventually reaching the Delaware River, Delaware Bay, and the Atlantic Ocean.
Mercer Lake was found to be relatively shallow, with a mean depth of 8.9 feet and a maximum depth of 18.5 feet. The total volume of water in the lake was estimated at around 2,560 acre-feet, or 834.2 million gallons. The survey also indicated significant sediment deposition in the eastern portion of the lake, with a total sediment volume of approximately 855,325 cubic yards. This pattern is likely due to the lake's role as a settling area for sediment carried by tributary inflows and stormwater discharges, which transport debris, leaf litter, and other materials into the lake.
Below is an image of the Bathymetric Survey that provides a detailed view of the sediment thickness contours measured in feet throughout Mercer Lake:
By establishing a detailed understanding of Mercer Lake's depth and sediment distribution, the bathymetric survey provides a robust foundation for the comprehensive lake management plan, informing long-term management decisions. The bathymetric data collected is also essential for evaluating the need for dredging, understanding aquatic plant colonization patterns, and predicting the lake's response to incoming nutrients, helping to guide restoration and protection efforts.
Hydrologic and Pollutant Loading Analysis is crucial for identifying the sources and impacts of pollutants entering a waterbody. It involves delineating watersheds, assessing hydrologic data, and evaluating nutrient loads.
For Mercer Lake, Princeton Hydro conducted an extensive analysis using tools such as USGS StreamStats and Stroud Research Center’s Model My Watershed®. This study provided a detailed understanding of the water and pollutant dynamics within the Mercer Lake watershed. The map below offers an aerial view of the watershed, illustrating the various types of land cover present within the area:
Runoff varied considerably between different sub-watersheds due to factors like land cover types, land-use consumption, impervious surfaces, and topography. Variations in elevation change also determine the impact runoff has on soil erosion, with steeper slopes causing higher erosion rates, especially if little vegetation is present. The chart below shows the various types of soil coverage in areas throughout the Mercer Lake watershed:
Princeton Hydro also assessed other pollutant sources, including groundwater seepage, streambank erosion, and contributions from residential septic systems. Additionally, the impact of waterfowl, particularly Canada Goose, was evaluated using nutrient loading coefficients. The presence of these birds significantly contributes to phosphorus and nitrogen levels.
The hydrologic budget, representing the water balance of the lake, was calculated by considering inputs such as direct precipitation, overland runoff, tributary inflow, and groundwater seepage. This data is vital for conducting trophic state analyses and determining the feasibility of various in-lake restoration techniques. Internal loading of phosphorus, which occurs when anoxic conditions in the lake's bottom sediments release bound phosphorus into the water, was also analyzed.
Results of the analysis revealed that Mercer Lake, covering 287.1 acres, is influenced by a watershed area of 20,551.4 acres, predominantly consisting of cropland and forested areas. The lake's shallow nature coupled with significant sediment deposition in the eastern portion, underscores the importance of managing both external and internal nutrient loads.
Understanding the hydrologic and pollutant dynamics through this detailed analysis allows for the development of a lake management plan that helps to prioritize management efforts, target the primary sources of pollution, and effectively address HABs.
Monitoring water quality is essential for understanding the existing chemistry of a lake, identifying trends, pinpointing problems, and assessing nutrient levels. It provides critical data that informs management decisions and helps maintain the health and stability of aquatic ecosystems.
For Mercer Lake, Princeton Hydro conducted thorough water quality monitoring from 2021 to 2023. This involved analyzing in-situ, discrete, and plankton data collected over three growing seasons. The monitoring focused on various parameters, including hypolimnetic anoxia and associated phosphorus dynamics, which are key contributors to HABs. The data collected offered a current assessment of the lake’s trophic state and plankton community, providing a baseline to document shifts in water quality in response to future management measures.
The Princeton Hydro team performed 13 sampling events at two consistent stations in Mercer Lake: a deep water station near the dam (ML-1) and a mid-lake station (ML-2). Various parameters were monitored, including water temperature, dissolved oxygen (DO), pH, specific conductivity, chlorophyll a, and phycocyanin, using an In-Situ AquaTROLL 500 meter.
Water samples were collected at both in-lake stations at the surface (0.5 meters) and near the bottom (0.5 meters above the sediment) using a Van Dorn water sampler. Samples were preserved appropriately and transported to the NJDEP-certified laboratory Environmental Compliance Monitoring (ECM) for analysis. The samples were analyzed for total phosphorus (TP), soluble reactive phosphorus (SRP), total dissolved phosphorus (TDP), nitrate-N, nitrite-N, ammonia-N, total suspended solids (TSS), and turbidity. Surface samples were also analyzed for alkalinity, chloride, and hardness.
Additionally, samples were collected for zooplankton and phytoplankton analysis, including species composition, dominant organisms, and relative density. Cyanobacteria (blue-green algae) genera were quantified to estimate cell counts, providing an approximate concentration of cyanobacteria cells per milliliter of water. Samples were also analyzed for the cyanotoxin microcystins using the Abraxis field testing methodology.
The team also evaluated local climatic conditions during the 2021 - 2023 seasons compared to the long-term average. These conditions, including temperature and precipitation, can have significant effects on water quality. The combination of increased precipitation and an increase in temperatures sets the stage for HABs proliferation. The charts below the monthly mean temperatures and monthly precipitation from 2021 – 2023 and the 30-year average; ‘normal’ refers to the monthly average over the 30-year period from 1991 – 2020.
The Water Quality Monitoring analysis revealed several key insights about Mercer Lake's water quality, and indicated that cropland runoff was the most significant source of phosphorus, a key driver of HABs. Hypolimnetic anoxia (the bottom layer of the lake becomes devoid of oxygen) was observed during all three field sampling seasons, contributing to internal phosphorus loading. The water quality monitoring also provided valuable information on the lake’s trophic state and plankton community.
Trophic State Modeling is a method used to assess the productivity of a lake by measuring the levels of nutrients, such as phosphorus, and the resulting biological activity. This assessment helps determine the lake's overall health and informs management strategies. The Trophic State Index (TSI) is a common tool used in this process, calculating index values based on phosphorus concentrations, chlorophyll a levels, and Secchi depths.
For MCPC, Princeton Hydro, utilizing data collected in the field and through lake and watershed modeling, estimated the nutrient status and biological activity of Mercer Lake. Here are a few examples of the models the team utilized:
By leveraging these sophisticated models, Princeton Hydro was able to gain a detailed understanding of Mercer Lake's nutrient dynamics and productivity. Many models were run twice: once for the watershed-based phosphorus load and once for the total combined load. This allowed for a comprehensive assessment of both external and internal nutrient contributions.
To mitigate pollutant loading issues, the Lake and Watershed Management plan outlines a series of Best Management Practices (BMPs) recommendations for implementation throughout the watershed, which include bioretention systems, wetland buffers, riparian buffers, and lakefront aquascaping. Such measures are designed to reduce nutrient loads, improve water quality, and enhance the overall ecological health of the lake and its watershed. By addressing the root causes of nutrient loading and implementing targeted management strategies, the MCPC is continuing their commitment to providing a sustainable and enjoyable recreational experience for park users while safeguarding the lake's ecological integrity.
Stay tuned for more updates as we continue to work with the MCPC on implementing the Mercer Lake and Watershed Management Plan, ensuring the watershed remains a vibrant and healthy resource for generations to come.
Regional watershed planning is crucial for maintaining the health and sustainability of interconnected waterbodies. By considering entire watersheds rather than individual lakes, we can develop more effective and comprehensive strategies to manage water quality, control pollution, and enhance ecological resilience. This holistic approach ensures that all elements within the watershed are addressed, leading to more long-lasting improvements.
Princeton Hydro’s efforts in developing and implementing management plans for Mercer Lake, Curlis Lake, Rosedale Lake, and Spring Lake demonstrate the power of coordinated, science-based planning. By leveraging detailed data and advanced modeling techniques, our team is able to create tailored solutions that meet the specific needs of each lake while contributing to the overall health of the region's aquatic ecosystems.
To read about another project we’re working on in Mercer County, check out our blog about Miry Run Dam Site 21. Through a blend of engineering and ecological enhancements, we are working with MCPC to revitalize 279 acres. With each phase, we edge closer to a vibrant, inclusive space that harmonizes nature and community.
As we reflect on the winter of 2023-2024, it's evident that New Jersey experienced another unusually mild season, mirroring the winter of 2022-2023. Notably, Lake Hopatcong, located in Sussex and Morris Counties, remained virtually ice-free throughout the winter, with only a brief period of minor ice formation in early January. This pattern was not isolated to Lake Hopatcong; many lakes across the state and the broader Mid-Atlantic region exhibited similar ice-free conditions. Such conditions can lead to increased algal and plant growth earlier in the year.
Adding to this, from January to early June 2024, 15 of New Jersey's 21 counties recorded precipitation levels 26% to 50% higher than their long-term averages. The remaining six counties, predominantly in the southern part of the state, had precipitation increases of 11% to 25% above their long-term normals. This heightened precipitation is significant as it can transport nutrients, most notably phosphorus and nitrogen, into water bodies, potentially fueling the growth of algae.
Compounding these factors, long-range climate models and trends suggest that the summer of 2024 could rank among the hottest on record. The combination of a mild winter, increased precipitation, and anticipated high summer temperatures sets the stage for conditions similar to those experienced in 2019, a year marked by widespread harmful algal blooms (HABs) in numerous lakes.
HABs, characterized by rapid overgrowths of cyanobacteria, present serious challenges to water quality and aquatic ecosystems. Cyanobacteria, or blue-green algae, naturally occur in aquatic environments but can proliferate rapidly under warm, nutrient-rich conditions. These blooms pose risks to human health, wildlife, aquatic species, local economies, and the overall ecological balance. The interplay between climate change and HABs is undeniable: rising temperatures and altered precipitation patterns foster conditions that exacerbate bloom occurrences.
Given these circumstances, it is crucial for lake managers and water utilities to adopt proactive measures. Early and consistent sampling efforts can detect cyanobacteria and akinetes, dormant spores that contribute to bloom formation. Additionally, reducing nutrient inputs, particularly phosphorus, into waterways is essential to prevent HABs. Princeton Hydro strongly recommends that lake managers, water utilities, and concerned community members closely monitor their lakes, reservoirs, and riverways to stay as proactive as possible in managing these valuable resources.
By raising awareness, fostering collaboration, and implementing effective strategies, we can work towards safeguarding the health and sustainability of our freshwater ecosystems. Together, we can address the challenges posed by HABs and protect the integrity of our water bodies. For more information about HABs, click here.
Dr. Fred Lubnow, Princeton Hydro’s Senior Technical Director, Ecological Services, is an expert in aquatic and watershed management, restoration ecology, community and ecosystem ecology, and the use of benthic macroinvertebrate and fish in-stream bioassessment protocols. Dr. Lubnow has managed hundreds of lake projects and provides technical expertise for a variety of lake and watershed restoration projects.
His experience in lake and reservoir restoration includes the design and implementation of dredging, aeration, chemical control of nuisance species, nutrient inactivation (i.e. alum) and biomanipulation. His experience in watershed restoration includes the design and implementation of structural Best Management Practices (BMPs), the development of Total Maximum Daily Load (TMDL) pollutant budgets, and the design, implementation and analysis of watershed-based monitoring programs.
400 native plants were installed along the western shoreline of Memorial Pond in Mount Arlington, New Jersey. The planting was completed in one day by a team of 20+ volunteers, staff members from Mt. Arlington Department of Public Works (DPW), Lake Hopatcong Foundation, Lake Hopatcong Commission, Princeton Hydro, and a generous community member who volunteered his excavating equipment (and time).
The planting initiative aims to prevent shoreline erosion, promote the growth of native species, increase wildlife habitat, and improve the water quality of Memorial Pond and Lake Hopatcong. Funding for this project was secured through a grant from the New Jersey Department of Environmental Protection, awarded to the Lake Hopatcong Commission in partnership with the Lake Hopatcong Foundation.
Memorial Pond is a 0.3-acre stormwater runoff basin that gradually releases into Glen Brook, which then flows into Lake Hopatcong. The pond receives sheet flow of stormwater from the adjacent road, which contributes to nutrient and sediment loading, thus locally reducing water quality in Memorial Pond and ultimately the waters of Lake Hopatcong.
Memorial Park, which includes Memorial Pond and Glen Brook, was identified by Princeton Hydro and the Lake Hopatcong team as a priority site for improvement, targeting initiatives that reduce pollutants and excessive nutrients entering into Lake Hopatcong.
Additionally, the pond’s steeply-sloped shoreline was bare and only stabilized with large rocks at the base of the banks. In the absence of stabilizing vegetation, the pond’s banks were experiencing erosion, and there was some concern about a few mature trees along the shoreline potentially falling into the pond.
The photos above were taken in April 2023 before the planting initiative.
The plant selection and layout were designed taking into account the steep slope and presence of mature, existing trees as well as focusing on regionally native plant species that will thrive and help stabilize the eroding shoreline. The planting team, led by Princeton Hydro Landscape Architect Jamie Feinstein, RLA and Aquatics Project Manager Pat Rose, was given precise instructions on how to install the plants to eliminate washouts and ensure the root systems can embrace the soil and hold it in place.
A variety of native herbaceous plants and shrubs were chosen for the site, including pennsylvania sedge, slender mountain mint, blue flag iris, sweet azalea, smooth hydrangea, and maple-leaved viburnum.
The plants will help reduce stormwater flow, absorb excess nutrients, prevent erosion, and ultimately decrease sedimentation to the pond, while creating a visually pleasing addition to the park and providing a habitat for pollinators and birds. Overall, this project promotes a healthier and more balanced ecosystem in Memorial Park.
The photos above were taken in July 2023 immediately after the planting initiative.
The installation of these beneficial plants is part of a series of water quality initiatives on Lake Hopatcong funded by a NJDEP Freshwater Harmful Algal Bloom (HAB) Prevention & Management Grant and 319(h) Grant awarded to Lake Hopatcong Commission in partnership with the Lake Hopatcong Foundation.
Additional initiatives included in the watershed implementation and HABs management plan are, the installation of:
floating wetland island (FWI), which are a low-cost, effective green infrastructure solution designed to mimic natural wetlands in a sustainable, efficient, and powerful way. FWIs improve water quality by assimilating and removing excess nutrients; provide valuable ecological habitat for a variety of beneficial species; help mitigate wave and wind erosion impacts; provide an aesthetic element; and add significant biodiversity enhancement within open freshwater environments;
biochar filtration bags, which improve water quality by removing phosphorus from waterbodies. Biochar can be placed in floatation balls, cages, or sacks, which are then tethered along the shoreline and in critical locations throughout the waterbody; and
nanobubble aeration system, which increases the concentrations of dissolved oxygen in the water, prevents stagnation of water, increases circulation, disrupts thermal stratification which provides “through-column” mixing, and minimizes the occurrence of HABs.
“Paired with biochar filters attached to buoys in the pond and continued monitoring and maintenance of the plantings by the DPW, these steps will set a healthy precedent for what can be achieved through working together with funders, local partners, science, and landscape architecture,” said Feinstein, who sourced plant material, provided logistics and co-led the planning and volunteer planting event along with Rose.
Princeton Hydro's Landscape Architect, Cory Speroff PLA, ASLA, CBLP, designed the planting plan, and Will Kelleher and Jackson Tilves from the Aquatics Team participated in the plant installation event with Feinstein.
Princeton Hydro is also authoring and supplying a maintenance manual that provides guidance on seasonal care of the plantings, when to remove the herbivory protection fencing, pruning, watering, and other activities that support the long term success of the planting initiative.
“This collaborative effort to enhance water quality serves as a prime example of how seemingly simple actions can have a meaningful impact on safeguarding our water resources for the benefit of future generations,” said the Lake Hopatcong Foundation.
The photos above from left to right: June 2023 before the planting; July 2023 during the planting (photo by Lake Hopatcong Foundation Executive Director Kyle Richter); and July 2023 immediately after the planting.
Princeton Hydro has been working on Lake Hopatcong, New Jersey’s largest Lake, for 30+ years, restoring the lake, managing the watershed, reducing pollutant loading, and addressing invasive aquatic plants and nuisance algal blooms. To read about some of the other projects we’ve recently worked on at Lake Hopatcong, click here.
Our lakes in New Jersey are an invaluable resource for clean drinking water, outdoor recreation, and agriculture and provide habitat for aquatic flora and fauna. Home to about 1,700 lakes, the “Garden State” is also the most densely populated state. Excess nutrients from fertilizers, roadway pollutants, overdevelopment, and failing septic systems can end up in our lakes and impair water quality. Larger rain events can also cause erosion and instability of streams, adding to the influx of more excess nutrients to our lakes and ponds. Changes in hydrology, water chemistry, biology, and/or physical properties in these complex ecosystems can have cascading consequences that can alter water quality and the surrounding ecosystem. For example, excess nutrients can fuel algal and plant growth in lakes and lead to issues like harmful algal blooms (HABs) or fish kills.
In order to ensure that we protect the overall health of our local waterbodies, it’s important that we look beyond just the lake itself. Implementing holistic watershed-based planning is a critical step in managing stormwater runoff, preventing the spread of HABs, and maintaining water quality. A watershed management plan defines and addresses existing or future water quality problems from both point sources and nonpoint sources of pollutants*. This approach addresses all the beneficial uses of a waterbody, the criteria needed to protect the use, and the strategies required to restore water quality or prevent degradation. When developing a watershed plan, we review all the tools in the toolbox and recommend a variety of best management practices to prevent nutrients from entering lakes or streams. Options include short- and long-term solutions such as green stormwater infrastructure, stream bank stabilization, and stormwater basin retrofits.
To reduce nutrient availability in lakes, one innovative tool in our toolbox is floating wetland islands (FWIs). FWIs are a low-cost, effective green infrastructure solution that are designed to mimic natural wetlands in a sustainable, efficient, and powerful way. They improve water quality by assimilating and removing excess nutrients; provide valuable ecological habitat for a variety of beneficial species; help mitigate wave and wind erosion impacts; provide an aesthetic element; and add significant biodiversity enhancement within open freshwater environments. FWIs are also highly effective in a range of waterbodies from big to small, from deep to shallow.
Typically, FWIs consist of a constructed floating mat, usually composed of woven, recycled plastic material, with vegetation planted directly into the material. The islands are then launched into the lake and anchored in place, and, once established, require very little maintenance.
It estimated that one 250-square-foot FWI has a surface area equal to approximately one acre of natural wetland. These floating ecosystems can remove approximately 10 pounds of phosphorus each year. To put that into perspective, one pound of phosphorus can produce 1,100 pounds of algae each year, so each 250-square-feet of FWI can potentially mitigate up to 11,000 pounds of algae.
In addition to removing phosphorus that can feed nuisance aquatic plant growth and algae, FWIs also provide excellent refuge habitat for beneficial forage fish and can provide protection from shoreline erosion.
Princeton Hydro has been working with Lake Hopatcong, New Jersey’s largest Lake, for 30+ years, restoring the lake, managing the watershed, reducing pollutant loading, and addressing invasive aquatic plants and nuisance algal blooms. Back in 2012, Lake Hopatcong became the first public lake in New Jersey to install FWIs. In the summer of 2022, nine more FWIs were installed in the lake with help from staff and volunteers from the Lake Hopatcong Foundation, Lake Hopatcong Commission, and Princeton Hydro. The lake’s Landing Channel and Ashley Cove were chosen for the installations because they are both fairly shallow and prone to weed growth. The installation of these floating wetland islands is part of a series of water quality initiatives on Lake Hopatcong funded by a NJDEP Harmful Algal Bloom Grant and 319(h) Grant awarded to Lake Hopatcong Commission and Lake Hopatcong Foundation.
Princeton Hydro partnered with the Greenwood Lake Commission (GWLC) on a FWI installation in Belcher's Creek, the main tributary of Greenwood Lake. The lake, a 1,920-acre waterbody located in both New Jersey and New York, is a highly valued ecological, economical, and recreational resource. The lake also serves as a headwater supply of potable water that flows to the Monksville Reservoir and eventually into the Wanaque Reservoir, where it supplies over 3 million people with drinking water.
The goal of the FWI Installation was to help decrease total phosphorus loading, improve water quality, and create important habitat for beneficial aquatic, insect, bird, and wildlife species. The project was partially funded by the NJDEP Water Quality Restoration Grants for Nonpoint Source Pollution Program under Section 319(h) of the federal Clean Water Act. GWLC was awarded one of NJDEP’s matching grants, which provided $2 in funding for every $1 invested by the grant applicant.
Measuring 630+ acres, Harveys Lake is the largest natural lake (by volume) in Pennsylvania and is one of the most heavily used lakes in the area. It is classified as a high quality - cold water fishery habitat (HQ-CWF) and is designated for protection under the classification. Since 2002, The Borough of Harveys Lake and Harveys Lake Environmental Advisory Council has worked with Princeton Hydro on a variety of lake management efforts focused around maintaining high water quality conditions, strengthening stream banks and shorelines, and managing stormwater runoff. Five floating wetland islands were installed in Harveys Lake to assimilate and reduce nutrients already in the lake. The islands were placed in areas with high concentrations of nutrients, placed 50 feet from the shoreline and tethered in place with steel cables and anchored. The FWIs were funded by PADEP.
Working with the Deal Lake Commission (DLC), Princeton Hydro designed and installed 12 floating wetland islands at two lakes in Asbury Park, NJ. In order to complete the installation of the floating wetland islands, our team worked with the DLC to train and assist over 30 volunteers to plant plugs in the islands and launch them into the two lakes. Our experts helped disseminate knowledge to the volunteers, not only about how to install the floating wetland islands, but how they scientifically worked to remove excess nutrients from the water. With assistance from Princeton Hydro, DLC acquired the 12 floating islands – six for Wesley Lake and six for Sunset Lake – through a Clean Water Act Section 319(h) grant awarded by NJDEP.
In addition to the direct environmental benefits of FWIs, the planting events themselves, which usually involve individuals from the local lake communities, have long-lasting positive impacts. When community members come together to help plant FWIs, it gives them a deepened sense of ownership and strengthens their connection to the lake. This, in turn, encourages continued stewardship of the watershed and creates a broader awareness of how human behaviors impact the lake and its water quality. And, real water quality improvements begin at the watershed level with how people treat their land.
For more information on watershed planning or installing FWI in your community, click here to contact us. To learn more about ANJEC, go here.
The Musconetcong River begins at New Jersey’s largest lake, Lake Hopatcong, and flows southwest for 42 miles before emptying into the Delaware River. At the headwaters in Lake Hopatcong, the community has been battling with harmful algal blooms (HABs). HABs can cause significant water quality issues in lakes and ponds, often forming a visible and sometimes odorous scum on the surface of the water. Blooms are primarily caused by warmer temperatures and increased amounts of nutrients (i.e., nitrogen and phosphorus) from stormwater runoff.
In 2019, the local community suffered immensely from HABs, which was the most prolific bloom the lake has experienced over the last two decades, resulting in public health advisories to be issued for recreation on the lake. Because Lake Hopatcong is a popular summer vacation destination, this outbreak unfortunately stunted the local economy, restricted recreational usage of the lake, and impacted fish and wildlife.
The Lake Hopatcong Commission and Lake Hopatcong Foundation, in partnership with municipalities, counties, the state, local groups like the Musconetcong Watershed Association, and Princeton Hydro, have been working to improve water quality for years by prioritizing stormwater mitigation and septic management policies within the watershed. So why was the summer of 2019 so intense?
Princeton Hydro scientists have been collecting water quality data in Lake Hopatcong for 30 years. This includes dissolved oxygen, pH, and temperature, as well as concentrations of total suspended solids, total phosphorus, nitrate‐N, ammonia‐N and chlorophyll a, and various biological factors. There are not many lakes in New Jersey that have such a robust and consistent public dataset, which presents a rare opportunity to study long-term trends. We dove a little deeper into this information to see what many have caused the 2019 blooms.
We analyzed a statistically significant dataset of surface water temperatures and found that average July surface temperatures in Lake Hopatcong have been steadily increasing over time. We also have 20+ years of observational data that documents an increase in frequency, duration, and magnitude of HABs over the same time period. In fact, HABs have recently persisted all the way into the winter months, enabling “green ice” to form on the lake surface, as observed in December 2020.
In summer of 2019, the Lake Hopatcong region was hit with a dramatic amount of rainfall. These weather patterns resulted in some of the highest early summer total phosphorus (TP) concentrations in Lake Hopatcong in over 20 years. The mean June TP concentration was 0.043 mg/L; the last time it exceeded 0.04 mg/L was in 1999. In order to have acceptable water quality conditions in the lake, the mean TP concentrations should be at 0.03 mg/L or lower.
It has been well documented that phosphorus is the primary limiting nutrient in Lake Hopatcong. Meaning, a slight increase in phosphorus can result in a substantial increase in algal and/or aquatic plant biomass. The water quality analysis identified the cause for the HABs (the high frequency of storms in June 2019 transporting nutrients, in particular phosphorus, to the lake) and identified why they persisted over the growing season (internal phosphorus loading).
Climate change is leading to more frequent, more intense rainstorms that transport run-off pollutants into waterways, coupled with hotter days to warm the water. The latest Intergovernmental Panel on Climate Change (IPCC) report, “AR6 Climate Change 2021: The Physical Science Basis,” confirmed that human influence has warmed the atmosphere, ocean, and land, and that this human-induced climate change is already affecting many weather and climate extremes in every region across the globe. It predicts, “increases in the frequency and intensity of hot extremes, marine heatwaves, and heavy precipitation, agricultural and ecological droughts in some regions, and proportion of intense tropical cyclones, as well as reductions in Arctic sea ice, snow cover and permafrost.” In the Mid-Atlantic region of the U.S., most climate models indicate that the landscape will become warmer and wetter.
Looking at our observations and 30-year dataset for Lake Hopatcong, our preliminary analysis shows that climate change — increased precipitation (which flushed the phosphorus into the lake) followed by intense heat to warm surface water temperatures — was a significant variable that led to the devastating HABs at Lake Hopatcong in 2019.
Other communities have experienced similar trends too. According to the U.S. Environmental Protection Agency, HABs have now been observed in all 50 states, ranging from large freshwater lakes, to smaller inland lakes, rivers, and reservoirs. Our neighbors in Upstate New York suffered from 1,000+ HAB occurrences during the 2019 season, including a HAB that covered 600+ square miles of Lake Erie causing beach closures and fish kills.
A study recently published in Nature journal reviewed three decades of high-resolution satellite data for 71 large lakes globally and determined that “peak summertime bloom intensity has increased in most (68%) of the lakes studied, revealing a global exacerbation of bloom conditions.” The study called for water quality management efforts to better account for the interactions between climate change and local hydrological conditions.
We are witnessing these impacts firsthand at Lake Hopatcong and within the Musconetcong River Watershed. And, according to the IPCC report, these climate change-induced instances (i.e. intense rainfall followed by intense heat) may become even more frequent. To further understand the connection between climate change and HABs at Lake Hopatcong, Princeton Hydro is conducting a more rigorous study that includes more distinct data. We hope this will provide some insight on how to manage expected climate impacts in lakes and watersheds.
While the IPCC report conclusions may be depressing, there is still much we can do at both a global and local level to limit future climate change. The key here is limiting cumulative CO2 (carbon dioxide) and CH4 (methane) emissions and quickly reaching (at least) net zero CO2 emissions. And, to specifically reduce occurrences of HABs While the IPCC report conclusions may be depressing, there is still much we can do at both a global and local level to limit future climate change. The key here is globally limiting cumulative CO2 (carbon dioxide) and CH4 (methane) emissions and quickly reaching (at least) net zero CO2 emissions. And, to specifically reduce occurrences of HABs fueled by climate change in Lake Hopatcong, eliminating sources of phosphorus from entering the lake is critical. So what can we do in the Musconetcong River Watershed?
In 2019, NJ Department of Environmental Protection committed $13.5 million via their Water Quality Restoration Grant programs for local projects that aim to improve water quality in New Jersey’s lakes and ponds. The Lake Hopatcong Commission landed a $500k grant via the program to evaluate and implement a variety of innovative, nearshore projects at Lake Hopatcong. Projects included performing an alternative non-copper-based algaecide treatment and one of the largest nutrient PhosLock treatments in the Northeast on the lake as well as the installation of Biochar bags, near-shore aeration systems, and floating wetland islands.
This could not be possible without the help of all project partners including Lake Hopatcong Foundation, Morris County, Sussex County, Jefferson Township, Borough of Hopatcong, Borough of Mt. Arlington, and Roxbury Township, who collectively contributed over $330k in match support. The Lake Hopatcong Commission also landed a subsequent $206,000 grant via NJDEP’s 319 program a few months later, with $44,000 in match support from the four municipalities and Lake Hopatcong Foundation and Commission, for the design and implementation of four in-lake/watershed projects to protect Lake Hopatcong's water quality.
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The results of these projects were significant. Over the last two years, the mean June TP concentrations were lower than 2019 (0.033 mg/L in 2020 and 0.020 mg/L in 2021). These in-lake and watershed efforts have had a positive impact on reducing available phosphorus.
Just this month, Lake Hopatcong Commission landed another $480k from a National Fish and Wildlife Foundation Delaware Watershed Conservation Fund grant, which was backed with $489k more in match support from Lake Hopatcong Commission, Lake Hopatcong Foundation, Musconetcong Watershed Association, NJDEP, Borough of Hopatcong, Township of Roxbury, Mount Arlington Borough, Morris and Sussex Counties, Lake Hopatcong Historical Museum, Rutgers University, NJ Highlands Council, and Princeton Hydro. The project team will design and implement three streambank stabilization projects in the watershed, which were identified as priority projects in the 2021 Upper Musconetcong River Watershed Implementation Plan.
“Managing loads of phosphorous in watersheds is even more important as the East Coast becomes increasingly warmer and wetter thanks to climate change. Climate change will likely need to be dealt with on a national and international scale. But local communities, groups, and individuals can have a real impact in reducing phosphorous levels in local waters.” Dr. Fred Lubnow, Director of Aquatics for Princeton Hydro
“Managing loads of phosphorous in watersheds is even more important as the East Coast becomes increasingly warmer and wetter thanks to climate change. Climate change will likely need to be dealt with on a national and international scale. But local communities, groups, and individuals can have a real impact in reducing phosphorous levels in local waters.”
To read the full article in the Musconetcong Watershed Association's "Instream Update" eNewsletter, click here.
The Musconetcong Watershed Association is an independent, non-profit organization dedicated to protecting and improving the quality of the Musconetcong River and its watershed, including its natural and cultural resources. Since 2003, Princeton Hydro has been working with MWA in the areas of river restoration, dam removal, and engineering consulting. Click here to read our Client Spotlight blog featuring MWA’s Executive Director Cindy Joerger and Communications Coordinator Karen Doerfer.
Volunteers recently came together in Asbury Park, New Jersey to install floating wetland islands (FWIs) in Wesley Lake and Sunset Lake. The initiative, led by the Deal Lake Commission and Princeton Hydro, brought together dozens of volunteers to install a total of 12 FWIs, six in each lake.
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Photos by Donald Brockel
FWIs are a low-cost, effective green infrastructure solution used to mitigate phosphorus and nitrogen stormwater pollution. FWIs are designed to mimic natural wetlands in a sustainable, efficient, and powerful way. They improve water quality by assimilating and removing excess nutrients that could fuel harmful algae blooms; provide valuable ecological habitat for a variety of beneficial species; help mitigate wave and wind erosion impacts; provide an aesthetic element; and add significant biodiversity enhancement within open freshwater environments.
Volunteers install plants in one of the six floating wetland islands launched in Wesley Lake:
The Deal Lake Commission acquired the 12 FWIs through a Clean Water Act Section 319(h) grant awarded by the New Jersey Department of Environmental Protection. During the volunteer event, participants helped plant vegetation in each of the FWIs, and launch and secure each island into the lakes.
We collected so many great photos during the event. Here are some highlights:
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NBC New York’s Brian Thompson stopped by to lend a hand and captured footage of the floating wetland island launch. Click here to watch!
To learn more about Floating Wetland Islands, check out the recent Native Plants, Healthy Planet Podcast, which featured Dr. Jack Szczepanski, CBLP, Princeton Hydro Senior Aquatic Ecologist.
Most of us are familiar with the famous quote "Alone we can do so little; together we can do so much.” This sentiment is at the center point of the Highlands Act and Regional Master Plan, which provides funding to help New Jersey’s Highlands communities take a proactive and regional approach to watershed protection.
Historically, private lake associations and municipalities have worked autonomously to address water quality issues and develop improvement plans. Working together, however, and taking a regional approach to lake and watershed management has much farther-reaching benefits. Taking an integrated approach helps improve water quality and reduce incidents of aquatic invasive species and harmful algal blooms (HABs) not just in one waterbody, but throughout an entire region.
The New Jersey Highlands Water Protection and Planning Council (Highlands Council) is a regional planning agency that works in partnership with municipalities and counties in the Highlands Region of northern New Jersey to encourage exactly such an approach. Created as part of the 2004 New Jersey Highlands Water Protection and Planning Act (the Highlands Act), the Highlands Council has funded numerous water-quality-related planning grants throughout the region.
“Watersheds are inherently regional; they don’t follow municipal boundaries. So the Highlands Council is in a unique position to address these challenges from that perspective,” says Keri Green, Highlands Council Science Manager. “It’s critical for municipalities to understand what is entering their lakes from the surrounding watershed before they can effectively address in-lake issues. Across the region, the stormwater inlets and roadways that encircle and affect lakes are owned and maintained by the municipalities, and when we can evaluate these inputs, we can plan for how to address impairments.”
In 2019, the Highlands Council funded a Lake Management planning grant for the Borough of Ringwood that adopted this wider watershed view, and would ultimately become a model for similar Highlands Council grants within the region. The Borough chose to engage the services of Princeton Hydro to support the project work.
“This regional approach to lake and watershed management is the obvious choice from a scientific, technical, and community point of view. Historically, however, this approach is rarely taken,” said Princeton Hydro’s Senior Project Manager, Christopher Mikolajczyk, who is a Certified Lake Manager and lead designer for this initiative. “We were thrilled to work with the Borough of Ringwood and the Highlands Council to set a precedent, which has opened the door for the Townships of West Milford and Rockaway, and will hopefully inspire the formation of more public-private lake management partnerships.”
Rockaway Township in Morris County, New Jersey received Highlands Council grant approval in January to complete a Lake Management Planning Study. Eleven small- to medium-sized lakes in the township are working together for a watershed assessment and comprehensive regional analysis, which will lead to the creation of a Watershed Implementation Plan (WIP). The WIP will recommend and prioritize key watershed management measures that will have big impacts on water quality improvement.
Given the large number of lakes in Rockaway Township, and in an effort to keep the study to a reasonable scope, a selection process occurred with input from the Township Engineering office, the Township Health Department, Princeton Hydro and the Highlands Council. The lakes in the Rockaway Township Watershed Management Program include Green Pond, Egbert Lake, Durham Pond, Lake Emma, Camp Lewis Lake, Lake Telemark, Lake Ames, Mount Hope Pond, Mount Hope Lake, White Meadow Lake, and Fox’s Pond.
“Rockaway Township has been proactive about implementing watershed improvement projects in the past, so we were happy to provide funding to support continuing their efforts focusing on these 11 lakes,” explains Lisa Plevin, Highlands Council Executive Director. “It was a very productive collaboration with Highlands staff working in partnership with the Township to develop an approach and Princeton Hydro preparing a scope of work that met everyone’s goals.”
The watershed assessment will entail a number of analyses, including watershed modeling; hydrologic and pollutant loading analysis; watershed-based and in-lake water quality assessments; and tropic state assessments. The assessment aims to:
Once all the lab data is processed, the watershed modeling is complete, and historical data reviewed, Princeton Hydro will create a General Assessment Report that will summarize the data/observations and identify which watershed management techniques and measures are best suited for immediate or long-term implementation. The team expects to complete the General Assessment Report in the spring of 2022, after a year's worth of 2021 growing season data has been collected.
In October 2020, the Highlands Council approved funding to support a watershed assessment of 22 private and public lakes in West Milford Township. The watershed assessment project is being implemented in two phases:
For Phase 1, which will take place throughout the course of 2021, Princeton Hydro will provide a historic data review; an examination of hydrologic/pollutant loads; a pollutant removal analysis; and watershed water quality analysis. The pollutants to be modeled include phosphorus, nitrogen, sediment, and bacteria, while the hydrology will include estimates of precipitation, runoff, evapotranspiration, groundwater flux, and ultimately streamflow or discharge.
This analysis will aid the Township in selecting, prioritizing and implementing nutrient and sediment load and stormwater management efforts with a focus on watershed projects that have the greatest overall benefit to the long-term management of surface water quality. The report will also identify examples of site-specific locations where wetland buffers, riparian buffers, and lakefront aqua-scaping can be implemented as part of future watershed management efforts.
For Phase 2 of the project, Princeton Hydro will investigate and assess the water quality of each of the lakes in West Milford Township during the growing season of May - October of 2022. This entails collecting bimonthly water quality samples at each lake, including in-situ water quality data consisting of real-time measurement of clarity, dissolved oxygen, temperature, and pH. The sampling events will also include a general survey of aquatic vegetation and/or algae growth, lake perimeter shoreline observations, and monitoring for nuisance waterfowl. These surveys will provide an objective understanding of the amount and distribution of submerged aquatic vegetation (SAV) and algae occurring throughout each lake over the course of the growing season.
The lakes included in this project are: High Crest Lake, Algonquin Waters, Lake Lookover, Kitchell Lake, Lindys Lake, Mt. Laurel Lake, Shady Lake, Wonder Lake, Mount Glen Lakes (Upper/Lower), Carpi Lake, Pinecliff Lake, Van Nostrand Lake, Upper Greenwood Lake, Post Brook Farms, Farm Crest Acres, Mt. Springs Lake, Forest Hill Park, Johns Lake, Gordon Lake, and Bubbling Springs Lake.
At the end of 2019, the Borough of Ringwood became the first municipality in New Jersey to take a regional approach to private lake management through a public-private partnership with four lake associations: Cupsaw, Erskine, Skyline, and Riconda.
The Borough of Ringwood is situated in the northeast corner of the New Jersey Highlands, is home to several public and private lakes, and provides drinking water to millions of New Jersey residents. In order to take an active role in the management of these natural resources, Ringwood hired Princeton Hydro to design a municipal-wide holistic watershed management plan that identifies and prioritizes watershed management techniques and measures that are best suited for immediate and long-term implementation.
Princeton Hydro recently completed a comprehensive assessment of the lakes and watersheds of Ringwood Borough. The assessment included a historical data review, hydrologic and pollutant loading analysis and in-lake and watershed based water quality data studies. The report details the results of Princeton Hydro’s mapping, modeling, and monitoring efforts in each waterbody and its respective watershed, along with specific recommendations for management implementations that are aimed at curbing the effects of nutrient and sediment loading, both within the lakes and their respective watersheds.
“Ringwood, West Milford, and Rockaway are three great examples of how people from different affiliations and backgrounds can come together to address lake and watershed monitoring and management,” said Mikolajczyk. “The key to success is open communication and a common goal!”
To learn more about Princeton Hydro’s natural resource management services, click here. And, click here to learn more about NJ Highlands Council and available grant funding.
Looking for a unique and creative way to manage nutrient runoff in freshwater lakes? Installing Floating Wetland Islands (FWI) is a low-cost, effective green infrastructure solution used to mitigate phosporus and nitrogen stormwater pollution often emanating from highly developed communities and/or argricultural lands.
FWIs are designed to mimic natural wetlands in a sustainable, efficient, and powerful way. They improve water quality by assimilating and removing excess nutrients that could fuel algae growth; provide valuable ecological habitat for a variety of beneficial species; help mitigate wave and wind erosion impacts; provide an aesthetic element; and add significant biodiversity enhancement within open freshwater environments.
“A pound of phosphorus can produce 1,100 lbs of algae each year. And, each 250-square foot island can remove 10 lbs of phosphorus annually.” explains Princeton Hydro Staff Scientist Katie Walston. "So, that's 11,000 lbs of algae that is mitigated each year from each 250 square foot of FWI installed!"
Typically, FWIs consist of a constructed floating mat with vegetation planted directly into the material. Once the islands are anchored in the lake, the plants thrive and grow, extending their root systems through the mat and absorbing and removing excess nutrients from the water column such as phosphorus and nitrogen.
The plants uptake a lot of nutrients, but the workhorse of the FWIs is the microbial community. The matrix used within the islands has a very high surface area and it promotes microbial growth, which performs the majority of the nutrient uptake. Additionally, the root growth from the plants continues to increase the surface area for the microbial biofilm to grow on. Both the plants and microbes acting together help optimize nutrient removal.
Princeton Hydro has designed and installed numerous FWIs in waterbodies large and small for the purpose of harmful algal bloom control, fisheries enhancement, stormwater management, shoreline preservation, wastewater treatment, and more. FWIs are also highly adaptable and can be sized, configured, and planted to fit the needs of nearly any lake, pond, or reservoir.
Recently, the Princeton Hydro team completed a FWI installation in Belcher's Creek, the main tributary of Greenwood Lake. The lake, a 1,920-acre waterbody located in both Passaic County, New Jersey and Orange County, New York, is a highly valued ecological and recreational resource for both states and has a substantial impact on the local economies. In addition, the lake serves as a headwater supply of potable water that flows to the Monksville Reservoir and eventually into the Wanaque Reservoir, where it supplies over 3 million people and thousands of businesses with drinking water.
Since the lake was negatively impacted by HABs during the 2019 summer season, Greenwood Lake Commission (GWLC) has made a stronger effort to eliminate HABs and any factors that contribute to cyanobacteria blooms for 2020 and into the future. Factors being addressed include pollutant loading in the watershed, especially that of Belcher's Creek. The installation of FWIs in Belcher's Creek will immediately address nutrients in the water before it enters Greenwood Lake and help decrease total phosphorus loading. In turn this will help reduce HABs, improve water quality throughout the Greenwood Lake watershed, and create important habitat for beneficial aquatic, insect, bird and wildlife species.
“In addition to the direct environmental benefits of FWIs, the planting events themselves, which involve individuals from the local lake communities, have long-lasting positive impacts,” said Dr. Jack Szczepanski, Princeton Hydro Senior Project Manager, Aquatics Resources. “When community members come together to help plant FWIs, it gives them a deepened sense of ownership and strengthens their connection to the lake. This, in turn, encourages continued stewardship of the watershed and creates a broader awareness of how human behaviors impact the lake and its water quality. And, real water quality improvements begin at the watershed level with how people treat their land.”
The project was partially funded by the New Jersey Department of Environmental Protection's (NJDEP) Water Quality Restoration Grants for Nonpoint Source Pollution Program under Section 319(h) of the federal Clean Water Act. As part of the statewide HAB response strategy, the NJDEP made $13.5 million in funding available for local projects that improve water quality and help prevent, mitigate and manage HABs in the state’s lakes and ponds. The GWLC was awarded one of the NJDEPs matching grants, which provided $2 in funding for every $1 invested by the grant applicant. For this project, the GWLC purchased the FWIs and NJDEP provided the 2:1 cash match in order for the GWLC to implement additional HAB prevention and mitigation strategies in critical locations throughout the watershed.
Over the coming weeks, our team will be in Asbury Park, New Jersey installing FWIs in Sunset Lake. Stay tuned for more! For additional information about our lake management services, go here: bit.ly/pondlake.
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To prevent harmful algal blooms (HABs) in New Jersey’s largest lake, a clay-based nutrient inactivating technology called Phoslock, is being applied in Lake Hopatcong this week. This is the largest Phoslock treatment to occur in the Northeastern U.S. The Phoslock treatment, which is happening in the southern end of the lake called Landing Channel, is expected to take approximately one week depending on the weather conditions.
Over the course of the 2019 summer season, Lake Hopatcong suffered from large-scale and persistent HABs causing local and county health agencies to close off all beaches and issue advisories over large sections of the lake. These unprecedented conditions had significant negative impacts on the ecological, recreational, and economic resources of the lake and region. In order to combat HABs in this upcoming 2020 summer season, the Lake Hopatcong Commission has partnered with the Lake Hopatcong Foundation, four municipalities (Jefferson, Hopatcong, Mt. Arlington, and Roxbury), two counties (Morris and Sussex), and their environmental consultant, Princeton Hydro, to develop both short- and long-term lake management strategies.
“The negative effects of HABs in our lake last year were numerous, widespread, and in some cases devastating,” recalled Donna Macalle-Holly of Lake Hopatcong Foundation. “It is imperative for every stakeholder to pool our resources to keep it from happening again. Collaboration is the only way to protect public health, as well as the health of New Jersey’s largest lake.”
In an effort to evaluate a variety of innovative in-lake and watershed-based measures to prevent, mitigate, and/or control harmful algal blooms in Lake Hopatcong, the Lake Hopatcong Commission was awarded a $500k grant as part of New Jersey Department of Environmental Protection’s (NJDEP) new $13.5M initiative to reduce and prevent future harmful algal blooms in New Jersey. In addition to the $500k grant, the aforementioned local government and nonprofit stakeholders provided $330k in matching funds to implement and evaluate a variety of ways to address HABs in Lake Hopatcong.
“Our lake community cannot sustain another year like 2019,” said Lake Hopatcong Commission Chairman Ron Smith. “Since the news of our grant award in early March, we have been working with our partners to make sure the projects are implemented in time for the 2020 season.”
This week, the water resource engineering and natural resource management firm, Princeton Hydro—a lake management consultant to Lake Hopatcong for over two decades—is implementing the first and largest innovative measure as part of the NJDEP HABs grant-funded project. This involves treating 50 acres of the southern end of the lake with Phoslock, a clay-based product that inactivates phosphorus in both the water column and the sediments, making this critical nutrient unavailable for algal growth. The Phoslock treatment, which requires proper permitting by NJDEP, is applied as a slurry and will be distributed from a boat. The slurry will temporarily make the water appear turbid, but should disperse approximately two to six hours after each treatment.
“We are expecting the Phoslock treatment to limit the growth of algae and therefore reduce the occurrence of harmful algal blooms in the lake this summer, keeping it open for recreation and business,” said Dr. Fred Lubnow, Director of Aquatic Resources at Princeton Hydro and leading HABs expert. “If this technology is deemed successful and cost-effective in Lake Hopatcong, we could set the precedent for large-scale HABs prevention in other lakes throughout New Jersey, and even across the nation.”
Developed by the Australian national science agency CSIRO, Phoslock is frequently used to strip the water column of dissolved phosphorus, as well as to inactivate phosphorus generated from deep, anoxic sediments. Recently, at a smaller scale, it has been shown to inactivate the mobilization of phosphorus from shallow sediments where there is a mobilization of phosphorus from both chemical and biological processes.
Algae uses phosphate, the biologically available form of phosphorus, as a food source to grow. When there is an excessive amount of phosphorus in a lake, algal growth can be dense and can negatively affect water quality. This excessive plant growth, caused by eutrophication, can both cause a lack of oxygen available, leading to fish kills, as well as produce harmful algal blooms with cyanotoxins, which are harmful to humans and pets.
After Phoslock is applied, it sinks through the water column, binding phosphate as it moves towards the sediment. Once settled at the bottom of the lake, it forms a very thin layer and continues to bind phosphate released from the sediment, thus controlling the release of phosphorus into the lake. One pound of phosphorus has the potential to generate up to 1,100 lbs of wet algae biomass. However, 1.1 tons of Phoslock is capable of removing 24 pounds of phosphorus -- that’s over 26,000 lbs of wet algae biomass not growing in the lake for every 1.1 ton of Phoslock applied. In turn, Phoslock’s ability to suspend biologically available phosphorus is therefore a major step towards improving a lake’s water quality.
As part of the NJDEP HABs grant funding, the stakeholder group will be evaluating the relative effectiveness of this treatment strategy. Because of its shallow depth and separation from the main lake, the Landing Channel area was a good candidate for evaluation of this technology. Princeton Hydro will conduct pre- and post-treatment monitoring of the Phoslock treatment area in order to conduct an objective evaluation of the cost effectiveness of the treatment as a means of preventing the development and/or mitigation of HABs. If the study indicates that Phoslock is a cost-effective treatment, the Lake Hopatcong Commission may consider additional trials in other sections of the lake, if funding is available.
Measuring 630+ acres, Harveys Lake, located in Luzerne County, Pennsylvania, just northeast of Wilkes-Barre, is the largest natural lake (by volume) within the Commonwealth of Pennsylvania, and is one of the most heavily used lakes in the area. It is classified as a high quality - cold water fishery habitat (HQ-CWF) and is designated for protection under the classification.
Since 2002, The Borough of Harveys Lake and the Harveys Lake Environmental Advisory Council has worked with Princeton Hydro on a variety of lake management efforts focused around maintaining high water quality conditions, strengthening stream banks and shorelines, and managing stormwater runoff.
Successful, sustainable lake management requires identifying and correcting the cause of eutrophication as opposed to simply reacting to the symptoms of eutrophication (algae and weed growth). As such, we collect and analyze data to identify the problem sources and use these scientific findings to develop a customized management plan that includes a combination of biological, mechanical, and source control solutions. Here are some examples of the lake management strategies we've utilized for Harveys Lake:
Floating Wetland Islands (FWIs) are an effective alternative to large, watershed-based natural wetlands. Often described as self-sustaining, FWIs provide numerous ecological benefits. They assimilate and remove excess nutrients, like nitrate and phosphorous, that could fuel algae growth; provide habitat for fish and other aquatic organisms; help mitigate wave and wind erosion impacts; and provide an aesthetic element. FWIs are also highly adaptable and can be sized, configured, and planted to fit the needs of nearly any lake, pond, or reservoir.
Five floating wetland islands were installed in Harveys Lake to assimilate and reduce nutrients already in the lake. The islands were placed in areas with high concentrations of nutrients, placed 50 feet from the shoreline and tethered in place with steel cables and anchored. A 250-square-foot FWI is estimated to remove up to 10 pounds of nutrients per year, which is significant when it comes to algae.
Princeton Hydro worked with the Harveys Lake Environmental Advisory Council and the Borough of Harveys Lake to obtain funding for the FWIs through the Pennsylvania Department of Environmental Protection (PADEP).
The shoreline habitat of Harveys Lake is minimal and unusual in that a paved road encompasses the lake along the shore with most of the homes and cottages located across the roadway, opposite the lake. In addition to the lake being located in a highly populated area, the limited shoreline area adds to the challenges created by urban stormwater runoff.
Runoff from urban lands and erosion of streambanks and shorelines delivers nutrients and sediment to Harveys Lake. High nutrient levels in the lake contribute to algal blooms and other water quality issues. In order to address these challenges, the project team implemented a number of small-scale streambank and inlet stabilization projects with big impacts.
The work included the stabilization of the streambank downstream for Harveys Lake dam and along Harveys Creek, the design and installation of a riparian buffer immediately along the lake’s shoreline, and selective dredging to remove sediment build up in critical areas throughout the watershed.
Hydrilla (Hydrilla verticillata), an aggressively growing aquatic plant, took root in the lake in 2014 and quickly infected 250 acres of the lake in a matter of three years. If left untreated, hydrilla will grow to the water’s surface and create a thick green mat, which prevents sunlight from reaching native plants, fish and other organisms below. The lack of sunlight chokes out all aquatic life.
In order to prevent hydrilla from spreading any further, Princeton Hydro and SePRO conducted an emergency treatment of the impacted area utilizing the systemic herbicide Sonar® (Fluridone), a clay-based herbicide. SonarOne, manufactured by SePRO, blocks hydrilla’s ability to produce chloroplasts, which in turn halts the photosynthetic process. The low-concentration herbicide does not harm fish, wildlife or people using the lake. Surveys conducted after the treatment showed it was working – the hydrilla had turned white and was dying off. Additional Sonar treatments followed and efforts to eradicate hydrilla in the lake continue.
Dr. Fred Lubnow, our Director of Aquatic Programs, estimates complete eradication of the aquatic plant could take around five years. Everyone can do their part in preventing the spread of this and other invasive species. Boaters and lake users must be vigilant and remove all vegetation from the bottom of watercrafts and trailers.
In 2009, Princeton Hydro developed a stormwater implementation plan (SIP) for Harveys Lake. The goal of the stormwater/watershed-based efforts was to reduce the lake’s existing annual total phosphorus load to be in full compliance with the established Total Maximum Daily Load (TMDL). This TMDL is related to watershed-based pollutant loads from total phosphorus (TP) and total suspended solids (TSS), which can contribute to algal blooms.
A number of structural urban runoff projects were implemented throughout the watershed. This includes the design and construction of two natural stream channel projects restoring 500 linear feet of tributaries and reducing the sediment and nutrient loads entering the lake. A series of 38 urban runoff BMPs, including nutrient separating devices and roadside infiltration, were installed in areas immediately adjacent to the lake to further reduce the loads of nutrients and other pollutants reaching the lake.
The photos below show a stormwater project that was completed in the Hemlock Gardens Section of the Watershed. Hemlock Gardens is a 28-acre section of land located in the southeastern portion of the watershed. It contains approximately 26 homes, has very steep slopes, unpaved dirt roads, and previously had no stormwater infrastructure in place.
Two structural stormwater BMPs were installed:
In 1994, Harveys Lake was identified as “impaired” by PADEP due to large algal blooms. In 2014, Harveys Lake was removed from the list of impaired waters. Project partners attribute the recovery of this lake to the stream restoration, urban runoff BMP implementation, and the use of in-lake nutrient reduction strategies.
The Harveys Lake Watershed Protection Plan Implementation Project proved that despite the lake being located in an urbanized watershed, it is possible to implement cost-effective green infrastructure and stormwater retrofit solutions capable of significantly decreasing pollutant loading to the lake.
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PRINCETON HYDRO
PRINCETON HYDRO