Water Resources in Rockland - Planning in a Changing World

Water Supply

Rockland County's water supply comes entirely from sources within the county's borders. Watersheds beyond the County's borders contribute to the Ramapo Valley Wellfield and Potake Pond. However, not all of the water in Rockland County stays there; some Rockland County water supplies the more populous Bergen County downstream.  The charts, maps and tables that follow provide an overview of the sources of water for domestic, commercial and industrial uses in Rockland County.


Rockland County Subwatersheds Draining Away From and Into the Hudson

Nine subwatersheds in Rockland County drain away from the Hudson, six of them extending beyond Rockland County borders into Bergen County (view fullsize pdf). Nine smaller watersheds, representing 21% of Rockland Country's watershed area, drain into the Hudson. (view fullsize pdf)

Rockland sub-watersheds draining away from Hudson

Rockland County Water Supply Sources

Rockland County Water Supply Sources
United Water NY 90%
Small Water Companies 7%
Private Wells (6,000 - 8,000) 3%

90% of Rockland County's water is provided by United Water of New York, whose sister company United Water of New Jersey provides water to neighboring Bergen County.  Many small water companies provide 7% of the county's water, to groups of from fewer than 50 customers to several thousand customers. The remaining 3% is provided by 6,000 - 8,000 private wells. (Miller, 2006) (view chart)


United Water's supply comes primarily from groundwater – 32% from 40+ bedrock wells in the central and eastern part of the county and 31% from the Ramapo Valley Well Field comprised of 10 shallow wells in the unconfined sand and gravel aquifers of the Ramapo and Mahwah River valleys. (view chart)

United Water New York Sources

United Water NY Water Supply Sources
Lake DeForest 37%
Alluvial well fields (includes Ramapo and Mahwah Valley well fields) 31%
Bedrock wells 32%
source: Paul Heisig, USGS 2009

Groundwater Resources in Rockland County

Rockland County United Water of New York Water Supply Wells

Groundwater supplies 61% percent of the drinking water to Rockland County. This map displays the approximate location of all 74 UWNY wells in Rockland County, by subwatershed, as of 2007. Sixty of the wells are active; the rest are test wells. From time to time existing wells may be disconnected from the system when water quality test results do not meet state standards and new wells may be brought into the system to supplement supply. (view fullsize pdf)

United Water of New York Water Supply Wells

Rockland County Wells of Small Water Companies and other Non-Individual Wells

In addition to United Water of New York wells and wells serving individual residences Rockland County contains139 wells serving small water companies and commercial, industrial and non-profit groups. This map displays the approximate location of these wells by subwatershed, as of 2007. While occurring in all the same subwatersheds as the UWNY wells, these wells are also found in 5 subwatersheds with no UWNY wells - 4 in the extreme northeastern portion of the county as well as Rockland County’s westernmost subwatershed. (view fullsize pdf)

Wells of Small Water Supply Companies etc.

Rockland County Sub-Basins Containing UWNY, Small Water Company, and other Non-Household Wells

The wells contained in this map represent those owned and operated by United Water New York (UWNY), as well as those owned by small water companies and other Non-Individual operations. The total land area of the Rockland County Watershed is 561.3 Square Kilometers. The total land area of Rockland County is 462.6 Square Kilometers. (view fullsize pdf)

Rockland County Sub-Basins Containing UWNY, Small Water Company, and other Non-Household Wells

The Rockland County Water Resources Assessment Project

The United States Geological Survey, in cooperation  with Rockland County and the New York Department of Environmental Conservation, began an assessment of water resources in Rockland County in 2004. The project was initiated because the Rockland County Department of Health reported that in 2000 and 2001 groundwater withdrawals approached or surpassed estimated aquifer recharge rates. The USGS noted that steady development of Rockland County in the past 40 years has both increased pumping and decreased recharge with the increased use of sewers and the increased area covered by impervious surfaces. The study will characterize the aquifer framework and provide a model of the aquifer which will help water managers in their efforts to ensure a sustainable water supply in Rockland County. Study results are available at USGS Rockland County Water-Resource Assessment. Click here for April 25, 2010 Presentation on USGS Study by Paul Heisig.



Rockland County Sub-Basins with USGS Stream Gages


Rockland County Sub-Basins
with USGS Stream Gages


How Old is the Groundwater in Rockland County?

Geochemists have studied the age of groundwater in the fractured bedrock aquifers underlying Rockland County by analyzing Helium, Neon and Tritium concentrations in the groundwater there. The results point to a residence time (time water has spent underground) of approximately 10-20 years. Details from this work have been provided to the USGS as input to their study efforts (Study of Ground Water Flow in a Fractured Bedrock Aquifer , Ground Water, Blackwell Publishing). Click here for April 25, 2010 presentation on The "age" of groundwater in Rockland County.



Surface Water Resources in Rockland County

Reservoirs and Streams

Surface water supplies 39% percent of the drinking water to Rockland County. Some surface water reservoirs located in Rockland County also supply water to northern New Jersey. This map displays the major surface water resources in Rockland County, including Lake DeForest, the Hackensack River and the Mahwah River. (view fullsize pdf)

Surface Water Resources - Reservoirs and Streams


Rockland County Peak Supply Capacity

Peak Supply is defined as the water available over a period of a few days. While peak supply capacity is 51.33MGD (millions of gallons per day). This peak supply is composed of 20MGD from Lake DeForest, 4MGD from the Ramapo Valley Well Field, 3MGD from Letchworth, and 24.33MGD from system wells (Distante, 2010). Based on proposed projects peak supply capacity is expected to rise to 54.46 in 2010 and 59.46 in 2019. (Miller, 2006)


Rockland County Average Supply Capacity

Average sustainable supply was 32-34MGD in 2006, 10MGD from Lake DeForest, 7-8MGD from the Ramapo Valley Well Field and 15-16 MGD from bedrock wells. Actual average daily demand for 2005 was 31.06 MGD. According to the County Hydrologist "The available total average capacity…must now be regarded as either insufficient or marginal."(Miller, 2006). United Water New York has responded with short-term actions and long-term plans.


Factors limiting Peak Supply Capacity

A number of factors limit the growth of peak supply capacity:

  • It is believed that groundwater is largely developed to full potential; the current USGS study of groundwater in Rockland County is expected to confirm or refine that belief.
  • In some cases the close spacing of production wells already results in interference between wells that limits production capacity. Most production well permits have a maximum allowable production rate of 8 gallons per minute.
  • NYSDEC surface water allocation permits also impose limitations. For example, the Ramapo Valley Well Field has additional limitations based on Ramapo River stream flow (no pumping when river flow drops below 8MGD).
  • Lake DeForest has withdrawal limits and the surface water treatment plant has capacity limits.
  • Periods of low precipitation cause further limits, both on surface water withdrawals and groundwater withdrawals, resulting from low reservoir levels and lower-than-average groundwater recharge.

Problems Generating Sufficient Peak Supply

Rockland County projects future demand based on historical demand trends, after removing from the analysis years in which demand is reduced by mandatory or voluntary conservation programs (more...).

According to Dan Miller, Rockland County Hydrologist, in his 2006 testimony to the NYS Public Service Commission, UWNY has an immediate problem satisfying peak demand.

"UWNY has generally been able to meet historical short-duration peaks, albeit with reduced water quality, by overpumping some of their bedrock wells and/or by requesting either mandatory or voluntary water conservation measures…UWNY's peak supply capacity has not been adequate since at least 1990… ….Lack of adequate water supply may soon result in severe limitations on the growth and economic development of the county….margin between demand and supply capacity is now so small that RCDOH is tracking all new additions to the system to monitor their peak demand and their effect on system performance."

Since 2006 United Water has submitted plans to increase long term supply and taken actions to increase supply in the short term.


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