Assessment of the Water Quality of Hook Pond, East Hampton, New York

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PROBLEM Hook Pond, an 83-acre freshwater pond in East Hampton, N.Y., has historically shown indications of impaired water quality. Impairments in this shallow pond include elevated nutrient concentrations and low dissolved oxygen concentrations in bottom waters as a result of current and historical land-use practices (Lombardo, 2015). Recent (2016) harmful algal blooms in Hook Pond and other e...

PROBLEM



Hook Pond, an 83-acre freshwater pond in East Hampton, N.Y., has historically shown indications of impaired water quality. Impairments in this shallow pond include elevated nutrient concentrations and low dissolved oxygen concentrations in bottom waters as a result of current and historical land-use practices (Lombardo, 2015). Recent (2016) harmful algal blooms in Hook Pond and other eastern Long Island freshwater bodies have spurred local concerns about the loading of nutrients from septic systems to groundwater (and ultimately to surface water), and land-use practices that contribute to contaminated stormwater runoff. To properly evaluate the basic ecological health of the pond, an understanding of the entire hydrologic system, including surface-water quality and contributions to it from both groundwater and contributing land uses, is needed. A critical first step is to establish a current baseline of conventional water-quality parameters for the pond as they vary under seasonal conditions. This baseline assessment would also account for spatial and depth variations in pond conditions, and those during wet weather events to better understand factors contributing to impairments.
 

BACKGROUND 


The Hook Pond Water Quality Improvement Study (WQIS) summarizes the recent water-quality data collection efforts in Hook Pond, its tributaries, and groundwater within its watershed by the U.S. Geological Survey (USGS) and other organizations (Lombardo, 2015). Between 2001 and 2008, the USGS collected seasonal and storm-related water-quality data for Hook Pond as part of a comprehensive monitoring program with the Towns of Southampton and East Hampton. Available field data include water temperature, pH, specific conductance, and dissolved oxygen from vertical profiles through the water column. Laboratory analyses of samples from the pond included those for nutrients, major ions, pesticides, and other organic compounds associated with human activities. The study was conducted to help understand the loading of nutrients to the freshwater systems on the South Fork of Long Island, including contributions from shallow groundwater. Additionally, the USGS has measured streamflow at one of the two tributaries to Hook Pond bi-annually (spring and fall) in the mid-1970s and from 2001 to 2008.
 
Other recent data collection efforts were conducted at Hook Pond but were limited to research efforts investigating algal blooms by academics and local agencies. These efforts are useful for understanding ecological impacts of the algae and associated toxins. However, they do not provide nutrient or field-parameter data at the frequency needed to understand the role of stormwater, irrigation, dredging, and groundwater in pond impairments. The Hook Pond WQIS identifies the perceived gaps in monitoring that would allow for informed decisions to be made about these factors, including an assessment of water quality throughout the pond vertically and across seasons and weather events. Although continuous water-quality and lake-level monitoring is suggested in order to document key daily variations in water chemistry, it is recommended that intensive water-quality sampling at select locations in Hook Pond and the Hook Pond tributary be conducted. These focused efforts would supplement planned and ongoing restoration efforts, such as Phragmites removal by The Nature Conservancy and the local residents and businesses (The Nature Conservancy, 2005), dredging to reduce sediment accumulation, and opening a pathway to the ocean (which would change the salinity and flow dynamics of the pond and adjacent groundwater). 


OBJECTIVE 


The primary objective is to provide data that will support the determination of the relative importance of the various nutrient sources contributing to algae blooms in Hook Pond. The establishment of a baseline of current water-quality conditions on a seasonal basis, to which weather and algal types and concentrations observed by Stony Brook University can be compared, would allow for the correlation of nitrogen and phosphorus speciation and concentrations in the pond. The proposed study would extend the record of waterquality and quantity information for dry and wet weather conditions against which future hydrologic changes and management actions may be compared. 
 
APPROACH 


An intensive water-quality sampling schedule will help establish a current baseline of physical and chemical conditions in Hook Pond and its tributaries prior to any planned or proposed stormwater management, pond remediation, or changes in land-use is implemented. Current data can then be interpreted in the context of historical data collected at Hook Pond by the USGS between 2001 and 2008. 


Hook Pond

Physical parameters will be collected along a vertical profile from six locations on Hook Pond and tributaries over an entire year—weekly from June to September, bi-weekly in fall and spring, and monthly from November to April (conditions permitting)—for a total of up to 28 sampling events. Parameters include water temperature, specific conductance, dissolved oxygen, phycocyanin and chlorophyll a, turbidity, pH, and clarity to provide information related to potential stratification and differences in quality based on depth, surrounding land use, and proximity to the two tributaries.
 

Water samples will be collected from the center of Hook Pond at a depth of half the water column and analyzed for organic and inorganic nitrogen, total phosphate, and orthophosphate at the USGS National Water Quality Laboratory (NWQL) in Denver, Colorado. These data would provide a continuation of historical data for basic trends analysis of physical parameters and nutrients in the pond on a seasonal basis, which could help determine how the chemistry of the pond has changed over the past 15 years. Three replicates and one equipment blank will be run for quality control. Samples and profiles would be conducted on a set schedule (set intervals and same time of day) for consistency. 


A continuous water-level, conductivity, and temperature recorder will be installed at the bridge across Hook Pond where the USGS has a bracket installed from a previous study—this bridge is a representative location for the overall lake level and temperature. A reading of water level will be taken every 15 minutes and transmitted in near real-time and available to the public. These high-frequency water-temperature and depth

data are important for understanding variations that this shallow pond may experience over short timeframe, particularly during precipitation or high wind events. Consistent and accurate temperature and conductivity data are needed to correlate with changes in water chemistry and algae blooms in the productive season. 


Water-quality samples will be collected at the mouth of the Hook Pond tributary and at a storm-drain outfall during two storm events. A pair of siphon samplers will be deployed at the mouth of Hook Pond tributary to collect water samples when the waterway reaches predetermined levels during a storm. These samplers could be set adjacent to storm-drain outfalls at different depths to collect samples sequentially as the water level rises. This would provide data on nutrient concentrations, pH, conductivity, and turbidity as stormwater enters Hook Pond. Collection will provide additional information necessary for loading calculations. 


Groundwater
Groundwater-level and water-quality monitoring of observation wells will be re-initiated to offer insight into groundwater contributions of nutrients to the pond and its tributaries from upland areas. Along with nutrient samples, groundwater would also be submitted for analysis by the USGS wastewater-indicator and (or) pharmaceutical methods, which are designed to identify wastewater (that is, septic) influence at low levels, and have been used throughout Long Island and the country to correlate wastewater-impacted waters with nutrient concentrations. 


Collectively, these data will allow for statistical analyses to be conducted and trends developed on spatial and temporal basis. Correlations between physical and chemical parameters can be determined in conjunction with weather and lake-level data. Concurrent stormwater and groundwater assessments would provide the data needed to establish an overall picture and develop loading models for Hook Pond. Implementation of management plans or changes in land-use practices that are expected to improve the waterquality in the pond could be assessed using the same approach to both compare to existing data and establish a new baseline moving forward.

 

REFERENCES 


Lombardo Associates, Inc., Hook Pond Water Quality Improvement Project: Lombardo Associates, Inc., Newton, Massachusetts, 291 p.

The Nature Conservancy, 2005. Phragmites in Hook Pond, Easthampton, N.Y.: The Nature Conservancy, unpublished internal report, 9 p.
 

Project Location by County

Suffolk County, NY