In 1931, the U.S. Supreme Court issued a decree that authorized and required the City of New York to release up to 440 million gallons of water per day (681 cubic feet per second{CFS}) to the Delaware River, from the two reservoirs it proposed in the watershed. One reservoir, Pepacton, was proposed for the East Branch of the Delaware River near Downsville, NY; the other was Cannonsville on the West Branch of the Delaware, near Stilesville, NY. The decision by the Supreme Court was based on a case the State of New Jersey brought against New York and New York City, to ensure adequate drinking water for its residents. 

The 1931 decree was amended and superseded on June 7, 1954 after New York City proposed a third reservoir, causing New Jersey to bring another case against New York City. The 1954 decree required New York City to divert an average 800 million gallons per day (MGD) (1,486 CFS) from all three reservoirs, or enough water from these reservoirs to maintain a minimum flow at Montague, NJ of 1,750 CFS. 

New York City never constructed the third reservoir. Nevertheless, the minimum flow requirement remains at 1,750 CFS. The 1954 Supreme Court decree also established the position of chief hydraulic engineer, also known as the Delaware River Master. The River Master’s duties are to ensure that the provisions of the 1954 decree regarding minimum flow requirements are met.

 What this all means is that when natural runoff from all Delaware River tributaries—including releases from the Mongaup River and Wallenpaupack hydro projects—collectively do not meet the target of 1,750 CFS, releases from NYC reservoirs are required to make up the difference. Most of the time that water comes from the Cannonsville Reservoir. 

To say the least, a complex number of water sources need to be taken into account when releases are required. The River Master must also take into account the time it takes that water, when called for, to reach Montague. The lag times for each system are as follows: Pepacton, 60 hours; Cannonsville, 48 hours; Neversink, 33 hours; and  Wallenpaupack, 24 hours. 

Release schedules are also complicated because the two hydro projects release more water during the week than on weekends, since the demand for electricity is lower.

In 1961, the states of New York, New Jersey, Pennsylvania and Delaware, along with the United States government, established the Delaware River Compact. This document ensures all the parties are involved in management issues related to flows in the Delaware  River.

In 1976, the NY State Legislature approved and Gov. Hugh Carey signed into law the water releases legislation. It required New York City to increase its minimum summer release from Pepacton to 70 CFS, Cannonsville to 325 CFS and Neversink to 45 CFS. The legislation also called for the commissioner of the Department of Environmental Conservation (DEC) to appoint a staff person to serve as the reservoir release manager. The duties of that position are to ensure that the regulations provided in the water release legislation are carried out. 

Years later, an in-depth analysis of the Upper Delaware Reservoir’s storage capacity, rainfall and other parameters resulted in the Flexible Flow Management Plan. As a result, summer releases were increased to 140 CFS from the Pepacton, 100 CFS from Neversink and 500 CFS from Cannonsville. Those releases are based on normal summer conditions and can change significantly depending on reservoir storage and rainfall. The increase in those releases helps meet the Montague flow.

When the water temperature at Lordville, NY on the Delaware River, reaches 75 degrees Fahrenheit, there are provisions in the water releases legislation and the Flexible Flow Management Plan to provide stress releases which will lower the water temperature and help the trout population. On several days in June of this year, releases from Cannonsville were increased from 500 CFS to 600 and even 800 CFS to reduce water temperatures to acceptable levels. There is a bank of 1.62 billion gallons of water set aside for this purpose during normal water years. 

As you can see from this rather brief overview, flow management in the Delaware River system is an extremely complex process. The Delaware River Basin Commission, the Delaware River Compact, the New York State DEC and the New York City Department of Environmental Protection all work in concert to meet drinking water needs in the basin and at the same time provide the cool water necessary to support the cold water fishery. 

In addition, 1,750 CFS keeps the salt front far enough downstream in Delaware Bay to prevent oyster drills from impacting the very valuable oyster fishery. 

Managing Delaware River flows is not an easy task, but is one that has been carried out successfully over the years. Cooperation between the states, federal government and New York City all play important roles in making that possible.  

For folks seeking more detail, web searches for the 1954 Delaware River Supreme Court decree, the Delaware River Basin Commission and the Flexible Flow Management Plan are good places to start. There is a huge amount of background data available on all these important program areas for interested parties.