FFMP 101

Determining Delaware River flows and their impact on the fisheries

Posted 4/5/18

Why it matters Everyone who fishes the Delaware is affected by the Flexible Flow Management Program (FFMP), the complex rules that govern the releases of water from the three New York City reservoirs …

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FFMP 101

Determining Delaware River flows and their impact on the fisheries


Why it matters

Everyone who fishes the Delaware is affected by the Flexible Flow Management Program (FFMP), the complex rules that govern the releases of water from the three New York City reservoirs on the Delaware’s headwaters: Cannonsville on the West Branch, Pepacton on the East Branch and the Neversink on the Neversink River. Your fishing experience on any given day will depend on the river’s height and the water’s temperature, both of which in turn depend on the reservoir releases that day. Since the trout in the Delaware need consistent flows of cold water to survive and reproduce, your fishing over the long run depends on the health of the fishery, which again is governed by the magnitude and consistency of the reservoir releases over time.

So, how are the reservoir releases determined under the FFMP? First, the Supreme Court decree of 1954 gave New York City (NYC) the right to build the reservoirs, but required that NYC maintain a minimum flow in the river of 1750 cubic feet per second at the USGS gage at Montague, NJ. The Montague flow target, still part of the FFMP, was intended to protect water supply 112 miles downriver at Trenton. But it was soon obvious that it was not sufficient to sustain the upper river’s trout fishery. With no environmental activism at the time of the decree, it is not surprising that the court made no provision for releases to protect the trout fishery.

Tony Bonavist’s article on page 3 details the struggles by environmentally conscious fishermen to correct this shortfall. Those efforts led to the imposition in 1976 of the first conservation releases and water-temperature targets by the New York State Department of Environmental Conservation (DEC). Though a step in the right direction, those releases were still too low, and since 1976, there has been a continual struggle by conservationists to modify the release policy to better support the fishery.

A step forward with FFMP 2007

Important progress was achieved with the adoption of the FFMP in 2007. The concepts underlying the FFMP were developed by a coalition of fishing conservation organizations, with the analysis done by Columbia University’s Water Center. The FFMP’s designers recognized that previous release policies hoarded water behind the reservoirs, thereby starving the fishery of the cold water needed during the summer, only to waste much of it later by letting it spill over the dams the following spring. The FFMP uses statistics from 70 years of Delaware River history to better balance NYC’s need for dependable water supply with the environmental requirements for adequate upper river flows.

It does so by using a commonsense approach: when the reservoirs are low, release less water; when the reservoirs are full and it’s safe, release more water. This approach attempts to keep the reservoirs at “normal” or safe levels, defined by seasonal curves, as seen in Figure 1, that are highest in early summer, when both NYC and the fishery need a supply of cold water, and lowest in the fall, when precipitation picks up and city usage drops.

A compromise among competing stakeholders

The design and management of a water-release policy such as the FFMP is no simple task. First, there are competing water claims by the stakeholders. NYC, which built the dams, diverts roughly half the water coming into the reservoirs for its own uses, while New Jersey also diverts water from the Delaware out of the basin into central Jersey. Water supply for both Trenton and Philadelphia depends in part on the Delaware, and serious flooding has happened along the river from just below the dams to just above Trenton. Then there is the impact of river flows biota such as the oysters in Delaware Bay and the federally endangered dwarf wedge mussels.

While in an average year there is enough water in the Delaware to meet these conflicting needs, a severe drought in the early 1960s proved that the Delaware’s waters must be managed prudently. NYC, New York State, Pennsylvania, New Jersey and Delaware, all having claims to the waters of the Delaware, were parties to the 1954 Supreme Court Decree and collaborated in the 1961 establishment of the Delaware River Basin Commission. Each Decree Party has veto power over changes to the release policy. The most recent—and quite bitter—dispute involved New Jersey’s veto in early 2017 to press its case for augmented water rights. Extensive negotiation among the Decree Parties under public pressure from the fishing community and the towns along the upper river, led to the 2017 FFMP agreement.

FFMP 2017: how does it work?

A federal employee, the Delaware River Master, is responsible for enforcing the provisions of the decree and of the FFMP, most particularly to assure that the Montague flow target is met. This is done by estimating future flows from meteorological data and the FFMP’s release rules. If that forecast is below the Montague target, the River Master directs the city to increase releases. (The underlying computations of these “directed releases” are posted weekly at https://water.usgs.gov/osw/odrm/)

Periodically, but no less than monthly, the New York City Department of Environmental Protection (DEP) estimates the amount of water that will enter its reservoirs and the amount of water it expects to divert from the reservoirs over the remainder of the water year (which ends May 31). Given the current storage and the targeted storage on May 31, DEP then computes its “Forecasted Available Water” (FAW) for release. This forecast guides the DEP in selecting one of six release tables labeled 4a through 4g of the FFMP. Low FAW implies use of table 4a, the stingiest releases, while high FAW allows use of table 4g, the most generous releases. These computations are also posted by the River Master. The conservation release for each day of the year is determined by the DEP based on the selected release table.

Where do we go from here?

Since its inception, FFMP has been superior to its predecessors. Partly thanks to generally adequate summer precipitation since 2007, reservoir levels have largely stayed in the “normal” range (see Figure 1), and hence releases and river flows have been consistent and adequate, and less water has been wasted in spillage. But there is still progress to be made.

For instance, detailed analysis by New York State and Pennsylvania fishery experts has shown that conservation releases can and should be higher than called for by FFMP. Then there are so-called “yo-yo” releases, directed releases to meet the Montague target that result in sudden and unnatural drops of river level that put the fish and the aquatic insects they feed on at peril. And there have been troubling episodes during summer heat waves, for example in July 2013, when river temperatures soared to potentially fatal levels for the trout. Although research done at the Columbia Water Center has shown that most of these thermal episodes can be mitigated by pulsed releases of additional cold water from the reservoirs, up until now such a program has not so far been implemented.

But help may be on the way for both thermal stress and yo-yo releases in FFMP2017, which banks water to address both problems. According to Delaware River Master Robert Mason, the Decree Parties, in consultation with him and the Delaware River Basin Commission (DRBC), are developing new protocols for use of that banked water to provide thermal relief and mitigate those rapid flow changes. The work plans are expected to be released this spring. The fishing community, continuing in the tradition of Tony Bonavist, Phil Chase, Frank Mele and others, will be following closely with an eye to ensuring and supporting further gains in the management of the coldwater fishery.


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