The Monhagen Brook’s Watershed spans 17.2 square miles (or 11,000 acres). It is one of 69 major tributaries to the Wallkill River, which is a major tributary to the Hudson River. The Watershed includes portions of three municipalities: the City of Middletown, the Town of Wallkill, and the Town of Wawayanda. It is fully within Orange County, New York.
The New York State Department of Environmental Conservation (NYSDEC) lists the Monhagen Brook as impaired due to pollution from both point and nonpoint sources. This status is proclaimed on the NYSDEC’s Priority Waterbodies List (PWL), which is an inventory of surface waters throughout the State that identifies and describes water quality concerns where they are known. The PWL designates four categories of impacts, which are listed in increasing severity as (from least to most impaired): 1) threatened, 2) stressed, 3) impaired, and 4) precluded. The Monhagen Brook is listed as impaired, with the primary pollutant being listed as phosphorus.
In response to interest and new funding available at the time to protect watersheds, OCWA applied for and was awarded a grant through the NYS DEC's Hudson River Estuary Program to fund the creation of a watershed plan for the Monhagen Brook. The project was a collaboration between the Orange County Water Authority, Orange County Department of Planning, and Orange County Soil & Water Conservation District. The Plan recommends strategies – many being site-specific – for protecting and enhancing this Watershed and for identifying and remediating sources of phosphorus pollution.