305b Groundwater Quality Monitoring in New York

Science Center Objects

Relatively little data describing the quality of groundwater in New York State exist, yet groundwater is used as a source of drinking water by approximately one quarter of the population of the state. The objective of the 305(b) groundwater quality monitoring project is to quantify and report on ambient groundwater quality from bedrock and glacial-drift aquifers in upstate New York.

An ongoing cooperative project between the U.S. Geological Survey (USGS) and New York State Department of Environmental Conservation (NYSDEC) Division of Water, this study supports NYSDEC’s responsibilities under Section 305(b) of the Clean Water Act Amendments of 1977. The resulting data set will be used to establish a groundwater quality baseline for New York State, characterizing naturally occurring, or background, conditions, and to identify long-term trends.

colored map of New York's 305(b) Major Basins

New York State 305(b) Major Basins(Public domain.)

Two to three of the 14 major hydrologic basins around the state are evaluated each year; in 2011 samples will be collected in the Mohawk River Basin and Western New York (Niagara and Allegheny River Basins, Lake Erie, and Western Lake Ontario Basins). Water samples are collected from domestic wells and public supply wells using standard USGS protocols (click here for an overview of how samples are collected). Samples are analyzed for a wide range of constituents, including physical parameters (such as pH and temperature), nutrients, major ions, trace elements including mercury and arsenic, Coliform bacteria, radon, total organic carbon, volatile organic compounds, and pesticides.

Groundwater quality samples are collected and analyzed using consistent, standardized methods. Fifty to sixty groundwater samples are collected each year from existing domestic and public supply wells using standard USGS protocols. Wells are selected to represent an approximately equal number of public and private wells, an approximately equal number of bedrock and glacial-drift wells, and to provide a representative geographic distribution of samples. Most private wells selected for sampling are identified through NYSDEC’s Water Well Program. The groundwater sampling parallels surface-water sampling done as part of the NYSDEC Rotating Integrated Basin Studies program (RIBS) program, and areas of the State (excluding Long Island, which is monitored through local County programs) are sampled once every five years.

The data are made available through the USGS National Water Information System and project reports. The project began in 2002 with a pilot study in the Mohawk River Basin, and sampling completed in 2008 represented the conclusion of a first round of groundwater-quality sampling throughout upstate New York State. As basins are sampled for the second and third time, approximately 20 percent of samples are collected from wells that previously have been sampled as part of this study. At the completion of the 2011 sampling season, more than 450 unique wells have been sampled as part of this project. Additional shale-gas-formation-relevant analyses, including dissolved-methane-gas concentration, were added in 2009.

map showing different colors for amounts of radon in groundwater in NY wells

Radon samples in New York groundwater wells(Public domain.)

map showing different colors for amounts of methane in groundwater in NY wells

Methane samples in New York groundwater wells(Public domain.)


USGS Ground Water and the Rural Homeowner
USEPA Ground Water and Drinking Water
USEPA Private Drinking Water Wells


NYSDEC Ambient Groundwater Quality Monitoring

NYSDEC Division of Water

NYSDEC Water Well Program

Drinking water standards

USEPA Current Drinking Water Standards

NYSDOH Current Drinking Water Standards


USEPA Radon in Drinking Water

USEPA Citizen's Guide to Radon

Results of the groundwater quality sampling have shown that groundwater quality in New York State is generally good, but can vary greatly depending on local hydrogeology and land use. The most common constituents to exceed existing or proposed drinking water standards include radon-222, iron, manganese, and coliform bacteria.

Examples of study-wide results are shown below for radon-222 and dissolved methane gas. The highest radon-222 activities detected, as much as 18,800 picocuries per liter, were found in samples collected from wells finished in crystalline bedrock. Radon-222 activities in many samples exceeded 300 picocuries per liter, part of a proposed drinking water standard, but few exceeded 4,000 picocuries per liter. Most samples had less than one milligram per liter of dissolved methane, but some samples had more than 20 milligrams per liter of dissolved methane. The maximum concentration of dissolved methane detected was more than 45 milligrams per liter in a sample from the Mohawk River Basin.


Basin Report                        Year                

Delaware River Basin 2015  In draft

Genesee River Basin 2015  In draft

St Lawrence River Basin 2015  In draft

Lake Champlain and Susquehanna River Basins 2014

Lower Hudson River Basin 2013               

Eastern Lake Ontario River Basin 2013 

Chemung River Basin 2013

Upper Hudson River Basin 2012

Oswego, Seneca, Oneida, and Central Lake Ontario Basins 2012

Mohawk River Basin 2011

Allegheny, Niagara, Lake Erie, and Western Lake Ontario Basins 2011

Delaware River Basin 2010

Genesee River Basin 2010

St Lawrence River Basin 2010

Lake Champlain Basin 2009

Susquehanna River Basin 2009

Chemung River Basin 2008

Eastern Lake Ontario River Basin 2008

Lower Hudson River Basin 2008

Oswego, Seneca, Oneida, and Central Lake Ontario Basins 2007

Upper Hudson River Basin 2007

Mohawk River Basin 2006

Allegheny, Niagara, Lake Erie, and Western Lake Ontario Basins 2006

Delaware River Basin 2005-06

Genesee River Basin  2005-06 

St Lawrence River Basin 2005-06

Lake Champlain Basin 2004

Susquehanna River Basin 2004-05

Chemung River Basin 2003

Mohawk River Basin 2002


Basin    Table of Sites     Map of Sites     Tab-delimited Data Table

Lower Hudson River Basin  Sites  Map   Data

Eastern Lake Ontario River Basin  Sites  Map  Data

Upper Hudson River Basin  Sites  Map  Data

Oswego, Seneca, Oneida, and Central Lake Ontario Basins (Finger Lakes)  Sites  Map  Data

Mohawk River Basin  Sites  Map  Data

Allegheny, Niagara, Lake Erie, and Western Lake Ontario Basins  Sites  Map  Data

Delaware River Basin  Sites  Map  Data

Genesee River Basin  Sites  Map  Data

St Lawrence River Basin  Sites  Map  Data

Lake Champlain Basin  Sites  Map  Data

Susquehanna River Basin  Sites   Map  Data

Chemung River Basin   Sites  Map  Data