Watershed Basin Identification Tools I. Purpose of project Introduction With 13 reservoirs and 3 controlled lakes in the 400-square-mile East-of-Hudson (EOH) New York City watershed, many watershed residents, understandably, are unfamiliar with the physical characteristics, water quality issues, and overlapping municipal boundaries of each reservoir basin or subwatershed. The reference material contained herein is intended to provide such information at a glance, to allow stakeholders to assess the water quality impacts of proposed development projects and zoning amendments in their districts, and to provide contact information for local and regional environmental groups that can offer guidance and assistance with citizen complaints and concerns about the management of their watershed. The EOH drinking water reservoirs and controlled lakes are fed by any combination of runoff from reservoir basin watersheds, aqueducts, streams and upstream reservoirs, and wastewater treatment plants (WWTPs). These same reservoirs are drained by a combination of calculated spills and releases, aqueduct discharges, and outside community withdrawals. The rate at which reservoir levels rise and drop fluctuates from year to year depending on local and regional precipitation levels. This means that reservoir surface area, volume, water intake and withdrawal also vary with fluctuations in annual rainfall. Land use characteristics within the 13 reservoir basins play an important role in the water quality of each reservoir: the greater the percentage of urban land use (impervious surfaces), the greater the volume of stormwater runoff and its associated impacts of nutrient and sediment loading. Therefore, water quality impacts also vary from year to year with corresponding fluctuations in rainfall and runoff. Land use in reservoir watershed basins is regulated to some extent by federal, state, and county governments, but the discretion to approve residential, industrial and commercial development is left largely to the towns that lie within the reservoir basins. Unfortunately, portions of the 13 EOH reservoir watershed basins are dispersed across 2 states, 4 counties, and 22 towns (in New York alone), which makes each basin subject to multi-jurisdictional land use regulations. Activities that affect a single reservoir’s water quality may be regulated by numerous discrete municipalities. For example, the Muscoot Reservoir Basin lies in Westchester and Putnam Counties, and the Towns of Lewisboro, North Salem, Southeast, Carmel, Somers, Yorktown, Bedford, and Pound Ridge lands. At the other extreme is the Town of Carmel, which covers portions of and therefore regulates land use in the Muscoot, Amawalk, Hudson River, West Branch, Middle Branch, Croton Falls, Lake Gleneida and Lake Gilead drainage basins. The purpose of this project is threefold. The first objective is to provide stakeholders with an easy reference toolbox that will familiarize them with the physical characteristics and dominant water quality issues of each EOH reservoir basin in the context of geographically discrete watersheds. This facilitates a holistic understanding of water quality impacts within the basins without the fracturing of imaginary municipal borders. The second objective is to integrate each reservoir basin with its adjacent watersheds, controlling municipalities and land use regulations. Once a basin is clearly defined and its water quality issues identified, stakeholders can examine the contributions of governing land use regulations to the protection or degradation of water quality in the subject basin. The third objective is to provide stakeholders with contact information for the local and regional environmental organizations that have a demonstrated interest in land use activities within the individual reservoir basins. This information will enable stakeholders to keep informed about proposed development projects and regulatory changes in their local communities and will provide a network of organized advocates whom they may contact with citizen complaints or when drafting comments on proposed projects. II. Discussion of Parameters Physical Characteristics Each reservoir is described in terms of its mean volume and surface area, maximum depth, and water input and output volume. The values for reservoir volume, surface area, input and output volumes are averaged for a 4- or 5-year period from 1992- 96 or 1993-96 because these values fluctuate from year to year with changes in annual rainfall. All data are taken from DEP’s Proposed Phase II Phosphorus TMDL Calculations (1999) for each reservoir, prepared by Dr. Kimberly Kane, Division of Drinking Water Quality Control. These data may be viewed on the Internet by inserting any EOH reservoir name before the .pdf extension at www.ci.nyc.ny.us/html/dep/pdf/kensico.pdf . The 5-year sampling period from 1992-96 represents average as well as widely fluctuating annual rainfall levels. For example, National Weather Service data for Yorktown Heights in the Muscoot Reservoir Basin show annual rainfall for 1992-1996 was: 1992 = 44.8” 1993 = 46.4” 1994 = 60.3” 1995 = 39.0” 1996 = 66.0” DEP’s annual water quality data for the 5-year sampling period therefore includes samples generated by flooding conditions (1996) and drought conditions (1995) as well as relatively normal rainfall conditions. As noted in the input and output values for some reservoirs, flow volumes may double between dry and wet years. In addition to the physical characteristics of the reservoirs, this study describes the geographical characteristics of each reservoir’s watershed or its basin, and identifies each reservoir’s source and receiving waters, adjacent reservoir basins, and any other significant water bodies and wetlands located in the subject basin. Water Quality Parameters The water quality parameters for each reservoir include trophic status,1 mean turbidity expressed in nephelometric turbidity units (NTU); sources of total phosphorus (TP); whether the reservoir is phosphorus-impaired; whether the reservoir lies within the 60-day travel time; and a brief analysis of the phosphorus TMDL calculation for each reservoir, including the TMDL in kilograms per year (kg/yr), point source Waste Load Allocation (WLA), nonpoint source Load Allocation (LA), current phosphorus load, and average phosphorus concentration expressed in micrograms per liter (µg/l). TP sources include percentage contributions from urban nonpoint sources (NPS), other NPS (which include forest, open space, and water), septic failures,2 SPDES-permitted wastewater treatment plants (WWTPs), and upstream sources. Regulating Municipalities This section identifies the townships that regulate land use activities within each reservoir basin (in the case of the easternmost basins, Fairfield County, CT regulates portions of the watersheds). This will assist stakeholders in assessing cumulative water quality impacts on a basin as well as regional level, identifying which municipalities are impacting water quality to greater and lesser degrees, and consolidating advocacy efforts toward the towns that are responsible for water quality protection within each individual reservoir basin. Land use in each reservoir basin is categorized by % urban use, forest, open space, and water. Open space land use includes agricultural activities. Where discrete sub-basins exist within a reservoir basin, land use data for each sub-basin are provided. Land use is considered to be urban when the phosphorus export coefficient3 reaches 1.8 kilograms per hectare per year (kg/ha/yr). A high but inconsistent percentage of urban 1 Trophic status indicates the degree of eutrophication, or the supply of nutrients supporting high biologic productivity in a water body. Those water bodies with high nutrient content are considered eutrophic; those with very low nutrient content are considered oligotrophic; those with moderate levels of nutrients are considered mesotrophic. 2 Phosphorus loading attributed to septic failures is considered NPS but is expressed separately here to identify those reservoir basins that have relatively high rates of septic failure. 3 A phosphorus export coefficient is an estimate of how much phosphorus is carried away in runoff from a particular land use area in one year. land use is impervious surfaces. For Westchester County reservoir basins, maps showing the density of imperviousness are supplied from the County’s web site.4 Environmental Organizations This section lists local and regional environmental organizations that have a demonstrated interest in water quality issues in each reservoir basin. It includes contact information for key persons in each organization. 4 See www.westchestergov.com/planning/environmental/stingEIS/DGEISfiles/AppendixFiles/Fig3.EI-17- 24.pdf Acronyms and Abbreviations kg Kilograms km2 Square kilometer(s). 1 km2 = 0.386 square miles. LA Load Allocation, the calculated amount of phosphorus generated from non-point sources that will achieve the Total Maximum Daily Load for a water body. m Meter(s) M G Million gallons, expressed as a yearly average. NPS Non-point source (pollution), or the pollution generated from stormwater runoff. NTU Nephelometric turbidity units, a measure of the clarity of water based on how much light is scattered by suspended particles. P Phosphorus TMDL Total Maximum Daily Load, the maximum amount of a pollutant, plus a 10% safety margin, that can enter a water body and still allow it to meet water quality standards, expressed in kilograms per year.