Client Spotlight: Roaring Brook Lake, Putnam Valley, NY

A Comprehensive Lake Management Plan Designed by Princeton Hydro

roaring-brook-lake Since 1998, Princeton Hydro has been working with the Town of Putnam Valley, often referred to as the Town of Lakes, to restore and maintain its waterbodies. The most recent area of focus is Roaring Brook Lake, a 115-acre man-made lake surrounded by a wooded landscape community that includes 260+ homes. The lake provides a variety of recreational opportunities for boaters, anglers, swimmers and outdoor lovers and is the center point of the Roaring Brook Lake District.

The Town of Putnam Valley and the Roaring Brook Lake District hired Princeton Hydro to conduct a thorough analysis of the lake’s ecological health, identify problems affecting the quality of the lake, and develop a detailed plan to improve and protect the lake. Specifically, Princeton Hydro will implement a detailed assessment of the lake that involves water quality monitoring, bathymetric mapping (measurement of lake depth and sediment thickness), aquatic plant surveys, and quantification of the lake’s hydrologic and pollutant budgets. These data will be utilized collectively to produce a comprehensive management plan for Roaring Brook Lake and its watershed.

Water Quality Monitoring

Water quality data are used to interpret the existing chemistry of the lake, identify water quality trends, pinpoint problems and assess nutrient levels.

At Roaring Brook Lake, Princeton Hydro will specifically collect in-situ data from the surface to the bottom of the water column. The resulting temperature, dissolved oxygen, pH and conductivity data will be used in combination with laboratory generated data to assess the lake’s thermal stability and investigate the potential for internal phosphorus loading. In addition, samples will be collected to identify phytoplankton and zooplankton in the lake; some of the plankton is considered a nuisance while others are considered valuable relative to the lake’s food web.

Bathymetric Assessment

The bathymetric assessment will generate accurate lake water depth, and provide sediment thickness and distribution data for the entire body of water. These data are then used to evaluate the need for dredging, asses how and where aquatic plants become colonized and other management options that can affect long-term decisions regarding the restoration and protection of Roaring Brook Lake. The bathymetric data are also used in the various trophic models that help predict the lake’s response to incoming nutrients.

Specifically, Princeton Hydro will utilize hydrographic surveying methods to conduct the bathymetric assessment of Roaring Brook Lake. A specialized dual frequency fathometer will be used to measure water depth and the thickness of the unconsolidated sediment present throughout the lake. The fathometer is directly tied into GPS, so data are consistently collected at the exact position of the survey transects. The GPS data and accompanying water depth data will be placed into a GIS format for the generation of morphometric data and bathymetric maps of the lake.

Aquatic Plant Mapping

Aquatic plants hold sediments in place, reduce erosion and provide habitat for fish and other important wildlife and insects. Although native aquatic plants are imperative to a lake’s health, an overabundance of these plants and the presence of invasive plants can have very negative impacts.

Princeton Hydro will be conducting a complete mapping of the aquatic plant community within Roaring Brook Lake to identify the plant species present in the lake, their relative abundance and location, and provide a basis for future evaluation of changes in the plant community. This data will greatly inform lake management activities moving forward. Additionally, with this data, Princeton Hydro will be able to assess the effectiveness of the resident grass carp – currently stocked in the lake – in keeping the submerged vegetation under control.

 

Hydrologic and Pollutant Budget

The hydrologic budget represents the water balance of a lake, accounting on an annual scale for all of the inputs and losses of water. The hydrologic data is used extensively in conducting trophic state analyses and is important in determining the feasibility and utility of many in-lake restoration techniques. At Roaring Brook Lake, Princeton Hydro will investigate and quantify four key components of the hydrologic budget, including direct precipitation, overland runoff (stormwater, snowmelt, etc.), tributary inflow and groundwater seepage.

Once the hydrologic budget is complete and land-use has been categorized and quantified, a pollutant budget can then be developed. The development of a detailed pollutant budget is a critical component of any lake management plan. For the purpose of the Roaring Brook Lake study, the term pollutant refers to the nutrients nitrogen and phosphorus as well as total suspended solids. The pollutant budget represents a quantification of the input of pollutants from various sources to the lake. Because the amount of nitrogen and phosphorus present in the lake stimulates eutrophication and results in water quality impacts, proper quantification of the nutrient load is critical for the development of a site-specific and cost effective management plan.

Data Analysis

The data analysis for Roaring Brook Lake will focus on identifying an acceptable in-lake condition (i.e. specific level of algal biomass in the lake) and correlate this to the lake’s annual phosphorus load through a robust water quality model.

The data analysis will involve the review of both historical and current data and will be used to identify correlations and relationships between existing pollutant concentrations/loads and unacceptable water quality conditions (i.e. algal blooms, high rates of turbidity, nuisance densities of aquatic plants, etc.). Water quality thresholds and goals will be established for assessing the long-term progress of the lake management plan.

Lake Management Plan

roaring-brook-lake-1Properly managing your lakes and ponds starts with developing a customized management plan and involves a holistic approach to ensure continued success.

A good management plan is informed by substantial data collection and analysis (as described above); includes any necessary permit requirements and a proposed timetable for implementation; provides recommendations for priority ranking of particular activities and restoration measures; and discusses predicted benefits of the plan’s implementation and how each activity is linked to the established water quality goals. A well-crafted and thorough lake management plan will also include a review of the various Federal, State, County and local grants, programs and initiatives that may provide funding for the identified in-lake and watershed projects.

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Princeton Hydro’s work with Roaring Brook Lake marks the 16th project they’ve conducted for the Town of Putnam Valley. Princeton Hydro’s proven success in watershed management stems from the cumulative training and experience of its staff, and its ability to develop watershed management solutions that are both practical and effective, which has led to the firm’s very high success rate in improving water quality.

If you’re interested in developing a customized, comprehensive management plan for your lake or pond, please contact us!

 

 

 

 

Tracking and Addressing Harmful Algae Blooms

Princeton Hydro’s PARE™ Program:
A Tool for Tracking and Addressing Harmful Algae Blooms (HABs)

Understanding HABs

Over the past decade we have learned more about the serious health implications associated with intense cyanobacteria (bluegreen algae) blooms. Although cyanobacteria are not truly algae, these blooms have come to be labeled Harmful Algae Blooms (HABs). Cyanobacteria have a number of evolved advantages relative to “good phytoplankton.” For example, many cyanobacteria are capable of fixing and assimilating atmospheric nitrogen, thus providing them with an unlimited source of a key growth-limiting nutrient. Most are also biologically adept at up-taking and utilizing organic phosphorus, another growth-limiting nutrient. Certain cyanobacteria can also regulate their position in the water column, thereby enabling them to capitalize on changing environmental conditions. HABsMany also are adept at effectively photosynthesizing under low light conditions. Finally, they are selectively rejected as a food source by filter feeders and zooplankton. These “life history” strategies enable cyanobacteria to rapidly out-compete phytoplankton and exploit their environment leading to a bloom.

It has been repeatedly documented that, under the correct set of conditions, HABs may generate very high concentrations of cyanotoxins. These toxins are used by cyanobacteria to achieve dominance in a lake, pond or river. Swimming in waters with even low concentrations of cyanotoxin may cause skin rashes (even for dogs and livestock), ear/throat infections and gastrointestinal distress. At high concentrations, cyanotoxins can impact the health of humans, pets and livestock. Drinking water contaminated by very high cyanotoxin concentrations can actually be lethal. Recently, increased attention is being given to possible links between cyanotoxins and neurodegenerative diseases, including Parkinson’s, ALS and Alzheimer’s.

The cyanobacteria of greatest concern include Microcystis, Planktothrix, Anabaena, Aphanizomenon, Oscillatoria, Lyngbya and Gloeotrichia. Different types of cyanotoxins are produced by these various cyanobacteria. The cyanotoxins receiving the most attention are Microcystin-LR and Cylindrospermopsin, but Anatoxin–a, Saxitoxins and Anatoxin-a(S) are also very problematic.

Regulatory agencies are still struggling to define what constitutes a “problem” and how to deal with HABs. For a number of years the World Health Organization (WHO) has used a provisional drinking water standard of 1 µg/L microcystin in drinking water. The US Environmental Protection Agency (USEPA) recently issued cyanotoxin guidance for drinking water that provides different action levels for children versus adults and for microcystin and cylindrospermopsin¹. Adding to the confusion, the majority of the States are still developing guidance and/or regulations concerning cyanotoxins in both drinking water and recreational waterbodies. As such, it is difficult to define when a bloom constitutes a problem and, more importantly, what action to implement to protect the health and welfare of the public, pets and livestock.

Cyanotoxins may be released into the environment by both living and dead cyanobacteria. However, the greatest concentrations occur as the cyanobacteria die and the cells break down –  something that is exacerbated by treating it with copper sulfate, which is the standard response to treating a bloom. Thus, “killing off” a bloom can actually make matters worse by quickly releasing large amounts of cyanotoxins into the water column. Once released into the environment, cyanotoxins are extremely stable and decompose slowly.

Common Misconceptions About HABs

There are a variety of common misconceptions about HABs, including: they occur only in the summer when water temperatures are elevated; they are unique to nutrient rich (hypereutrophic) systems; they are driven solely by elevated phosphorus concentrations; and they are most likely to occur under stable (stratified) water column conditions. The most potentially harmful misconception is that HABs can be cured by treating them with copper sulfate; because, as noted above, copper sulfate treatments can actually make things worse.

The above “typical conditions” don’t always lead to a HAB, and blooms with elevated cyanotoxin levels may occur even in nutrient-limited waters or under environmental circumstances that deviate from the “norm.” To further complicate matters, not all cyanobacteria are associated with HABs, cyanotoxin producers may not always produce cyanotoxins, and the taste and odor compounds often associated with HABs may be generated by non-HAB algae species. As such, the only definitive way to understand if a waterbody suffers from, or is in danger of suffering from, a HAB is to collect the proper data. This includes:

  • Quantification and speciation of the phytoplankton community
  • Collection and analysis of Chlorophyll a
  • In-Situ measurement of
    • Dissolved oxygen
    • Temperature
    • pH
    • Secchi disk depth
  • Collection and analysis of
    • Phosphorus (TP, SRP, DOP and DIP)
    • Nitrogen (Nitrate and Ammonia)
  • Measurement of taste and odor compounds
    • Geosmin
    • 2-methylisoborneol (aka MIB)
  • Analysis of the amount of Microcystin present in the water column.

To date, cyanotoxin testing has been expensive and the data turn-around slow.

A Strategy for Tracking and Managing HABs

To help understand and monitor HABs, Princeton Hydro recently launched a multi-prong strategy called PARE™ (Predict, Analyze, React, and Educate). Princeton Hydro’s PARE™ program focuses on the importance of thoroughly understanding site conditions, properly tailoring action programs and sustaining management efforts that go far beyond simply treating a bloom. As noted above, the PARE™ program consists of four key, interrelated elements:

  • Predict – Forecast a bloom using a long-term database of keystone parameters, and/or remote sensing techniques
  • Analyze – Quantify a bloom’s severity by measuring key diagnostic parameters including Microcystin
  • React – Implement measures to prevent, control or terminate a HAB
  • Educate – Share information with and educate the community about HABs

Predict

Ideally, to successfully predict HABs, it is paramount to measure the amounts of phosphorus, nitrogen, and chlorophyll in the water column, track dissolved oxygen and water temperature profiles, and identify the types and densities of cyanoWater Quality Databacteria and phytoplankton. Overall, in order to effectively predict the onset, magnitude and duration of a HAB, it is necessary to have a good data foundation.

Analyze

With an adequate database, it becomes possible to develop algorithms that account for all of the chemical, hydrologic and physical variables that may lead to HABs, including seasonal differences in weather and precipitation. In some cases it may also be possible to utilize remote sensing technology to track bloom development.

With a suitable database, it becomes possible to develop HAB thresholds based on:

  • Phytoplankton densities (cell counts)
  • Bloom indicators
    • Declining Secchi disc clarity : < 1 meter)
    • Chlorophyll a concentration: >20 µg/L)
    • MIB concentration : >10 ng/L
    • Geosmin concentration: > 10 ng/L

As part of PARE™ we also now have the ability to quickly and effectively measure the concentration of Microcystin in the water column using a combination of rapid response field test kits and accurate, quick-turnaround laboratory analyses.  The Microcystin data can then be compared to established USEPA or, when available, state guidance concentrations for cyanotoxins in drinking water and recreational water.

React

The data that are generated from the Predict and Analyze elements of the PARE™ program enables us to know when aChart bloom is about to occur or has developed, and quantify the severity of the bloom.  The many variables that may lead to HABs interact in a complex manner in lake and pond ecosystems. Manipulating the ecosystem to prevent or treat HABs requires extensive expertise.  

Some of the interactions that must be taken into consideration include:   

Biological linkages and interactions

  • Nitrogen fixers versus non-nitrogen fixers
  • Early blooming species potentially setting the stage for more problematic later blooming species
  • Zooplanktivory and the role of the fishery in stimulating a bloom or creating the environmental conditions supportive of a bloom
  • Nitrogen/Phosphorus ratios as well as the type, availability and sources of these primary nutrients

Through the correct understanding of these interactions it becomes possible to properly React by designing and implementing various pre-emptive controls and corrective measures such as:

  • Aeration and mixing,
  • Use of nutrient inactivators (alum, PhosLock® and alum surrogates),
  • Ozone,
  • Biomanipulation of the fish and plankton communities, and
  • Limited, properly timed algaecide applications.  

On a larger, long-term scale, the React element of the PARE™ program encompasses watershed management programs targeting nutrient load reductions that can actually reduce bloom frequency/intensity.  

Although the React element recognizes the role of algaecides as a potential part of the solution, it does not condone repeated extensive treatments with copper sulfate.  As noted above, relying solely on substantial copper sulfate treatments most often only triggers worse conditions and leads to spiraling, repetitive blooms.

Education and Outreach

Besides informing the public about health concerns related to cyanobacteria and HABs, it is important that stakeholders are also informed about measures that they can implement to help prevent blooms.  This includes “on-lot” nutrient controls such as septic management, limited application of lawn fertilizers, creation of shoreline buffers and waterfowl control. It is also necessary for stakeholders to understand the lifecycle of HABs, that ongoing monitoring and management help address HABs before they peak, and that, while seeming to be the “magic bullet,” copper sulfate is not the proper management tool.

Implementing PARE™

Begin PARE™ early, with the sampling of the above-noted key water quality Sampling Kitparameters and bloom initiated in early spring.  Then sample on a regular basis over the entire course of the growing season, especially in the summer when cyanobacteria problems emerge and peak. This information will become the foundation of the comprehensive database used to make timely management decisions.  The key is to be in a position to predict the onset of a bloom so that management actions can be implemented in a proactive, as opposed to reactive, manner.  Microcystin sampling can be focused on beach areas or around water intakes.  Begin with the simple, test-strip rapid response, in-field testing and, when necessary, use the laboratory analyses to confirm or further quantify whether a bloom has triggered a cyanotoxin problem.  If there is early evidence of a cyanobacteria bloom, implement the proper measures needed to control the bloom.  While bloom control measures are being implemented, continue to collect and analyze the microcystin data to confirm that the implemented measures have improved water quality and that conditions are safe for the ingestion of the water or the recreational use of the lake. After achieving specific water quality and HAB control goals, continue to implement the measures needed to track conditions and prevent/react to future blooms.  This will further facilitate the ability to respond to and control cyanobacteria blooms.

For more information about HABs and PARE™ come see us at the upcoming Pennsylvania Lake Management Society (PALMS) Conference. Click for details.


¹0.3 µg/L for microcystin and 0.7 µg/L for cylindrospermopsin children < than school age. For all others 1.6 µg/L for microcystin and 3.0 µg/L for cylindrospermopsin.