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Prepared in cooperation with Rockland County and
New York State Department of Environmental Conservation

Rockland County Water-Resource Assessment

Project Summary:

Summary of Results from the USGS Water-Resource Investigation of Rockland County, New York, 2005-2007

In 2004, concerns over the sustainability of water resources in Rockland County, New York prompted an assessment of the hydrogeology of Rockland County by the U.S. Geological Survey. The investigation included a review of all resources, but focused on the Newark Basin aquifer, a fractured, sedimentary bedrock aquifer over which nearly 300,000 people reside. About 12.7 billion gallons of water were used in Rockland County in 2005, about 35 percent of which was withdrawn from the bedrock aquifer. A regional conceptual model of the aquifer framework was developed and integrated with other hydrogeologic data to define the regional groundwater flow system. Groundwater flow within the aquifer is largely constrained by the strike of the dipping conglomerate, sandstone, and siltstone bedrock units, as the most productive water-bearing fractures are subparallel to the bedding of these units.

Review of pumpage and water-level data from the bedrock aquifer back to 1989 suggests that there has not been a continuous downward trend in groundwater levels across the aquifer. Groundwater levels have locally declined in response to new stresses from production wells, especially when they have been used continuously. The greatest concern regarding sustainability of groundwater resources is the aquifer response to the annual increase in pumpage from May through October (a 25 percent average increase in 2005). Streams are also affected by seasonal groundwater pumpage; nearly all streams in the productive west-central area of the aquifer ceased to flow during the dry late summer of 2005. Annual recharge estimates from 1961 streamflow data range from 15 to 25 inches; this variation arises from differences in precipitation, overburden thickness, and percent of impervious cover across the aquifer. Sustainability of water resources in Rockland County is largely dependent on: (1) the ability to adjust water-use during drought periods and during summer peak-demand periods, and (2) to avoid loss of supply from groundwater contamination.

Rockland handout image

       Rockland County Location Map       

Rockland powerpoint image


Heisig, P.M., 2010, Water resources of Rockland County, New York, 2005–07, with emphasis on the Newark basin bedrock aquifer: U.S. Geological Survey Scientific Investigations Report 2010–5245, 130 p., at

Yager, R.M. and Ratcliffe, N.M., 2010, Hydrogeology and simulation of groundwater flow in fractured rock in the Newark basin, Rockland County, New York: U.S. Geological Survey Scientific Investigations Report 2010–5250, 137 p., at

Author contact information:

   Paul Heisig
tel. (518) 285-5648
       Dick Yager
tel. (607) 266-0217 x3004

Abstract of study findings presented at the "State of the Hudson River Watershed" conference, September 28, 2009 at Hyde Park, NY.

Lamont-Doherty Video image Video of presentation at Lamont-Doherty - April 25, 2010
Rockland Fact Sheet image 2 page Summary of Selected Study Findings
Rockland powerpoint image PowerPoint of Selected Study Findings

Previous USGS studies of Rockland County water resources:

Perlmutter, N.M., 1959, Geology and ground-water resources of Rockland County, New York: New York State Water Power and Control Commission Bulletin GW-42, 133 p. "LIZARDTECH", at

Moore, R.B., Cadwell, D.H., Stelz, W.G., and Belli, J.L., 1982, Geohydrology of the valley-fill aquifer in the Ramapo and Mahwah Rivers area, Rockland County, New York: U.S. Geological Survey Open-File Report 82-114, 6 sheets, scale 1:24,000. "LIZARDTECH", at

USGS Reports on groundwater resources of The Nation, and nearby Northern Atlantic Coastal Plain aquifer system:

Reilly, T.E., Dennehy, K.F., Alley, W.M., and Cunningham, W.L., 2008, Ground-Water Availability in the United States: U.S. Geological Survey Circular 1323, 70 p., also available online at

Masterson, J.P., Pope, J.P., Monti, Jack, Jr., and Nardi, M.R., 2011, Assessing groundwater availability in the Northern Atlantic Coastal Plain aquifer system: U.S. Geological Survey Fact Sheet 2011–3019, 4 p., at

Maps (Poster-Size):

Map Figures

Poster-size PDFs (georeferenced 24"x32") of figures 7, 9, 11, 16–18, 20, 29, 30–32, 37–40, and 46–47 in the Heisig (2010) report.

Map Figures

Note: In Acrobat Reader, activate "Layers" along left edge, then click eye to turn on/off map features. (View -> Show/Hide -> Navigation Panes -> Layers)

GIS Dataset:

Index view of

Metadata for RocklandGIS_sir2010-5245_gdb_metadata.htm (Rt-Click -> Save Target As; Note- 14MB but unzips to a 632MB ESRI GeoSpatial Database [gdb] composed of 231 files)

Index view of

Metadata for RocklandGIS_sir2010-5250_gdb_metadata.htm (Rt-Click -> Save Target As; Note- 65KB but unzips to a 305KB ESRI GeoSpatial Database [gdb] composed of 52 files)

Interactive Data Applications:

Real-time dataHydrologic data collection by the USGS in Rockland County and Northern New Jersey (Real time -- data downloads every 1 to 4 hrs)

Groundwater Model:

This ZIP Archive contains files to run the groundwater flow simulations with SUTRA documented in:
Yager, R.M. and Ratcliffe, N.M., 2010, Hydrogeology and simulation of groundwater flow in fractured rock in the Newark basin, Rockland County, New York: U.S. Geological Survey Scientific Investigations Report 2010–5250, 137 p., at

Separate folders are provided for two model domains: the Spring Valley well field model (SValley) and the regional model of the Newark Group aquifer (Regional). These folders each contain subfolders for "input" and "output" for two alternative models (A and B) based on different interpretations of the strike of bedding. An "ancillary" folder is included for each model domain that contains Argus input files, Excel spreadsheets and shapefiles used for viewing with Modelviewer. A "source" folder is also included with versions of: SUTRA, UCODE & Modelviewer. The "ancillary" folder contains: (1) Perl scripts used to construct data sets, (2) files for pre- and post-processing using Argus and Excel, and (3) a GIS shapefile overlay. An additional folder entitled "run" is also included to simplify viewing the model results and to enable parameter substitutions with UCODE.

Readme.txt for

Index view of (Note: HUGE 3.6GB Zip File! Rt-Click -> Save Target As during off hours. Recommend emailing for a DVD)

Impervious Runoff Video:

Storm runoff from impervious surfaces video VIDEO of storm water runoff during summer thunderstorm showing effects of impervious surfaces.

Selected Illustrations:

Changes in Water Use, Population, and Road Miles in Rockland County, NY Estimated Water Use in Rockland County (2005) Example of Annual Pumpage and Groundwater-Level response at a supply well
Conceptualization of Regional Groundwater Flow in Dipping Sedimentary Bedrock of Rockland County, NY How the Dip Angle of Sedimentary Bedrock (and Water-bearing Fractures) Affects the Updip Areal Extent of Production Well Capture Zones Changes in Chloride Concentration Over Time at Production Wells, Rockland County, NY
Peak Flow Responses in Streams Whose Watersheds have Different Percentages of Impervious Surface Estimates of Recharge across Rockland County, NY from a Temporary Streamflow Gaging Network Cumulative Treated Wastewater Discharge to the Hudson River, Compared with Precipitation, UWNY Water Withdrawals, and Stage (River Water Level Height) in the Mahwah River

Related Links:

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Page Last Modified: Wednesday, 27-Apr-2016 16:22:44 EDT