APRIL 30, 2015
The
Delaware River Basin Commission (DRBC) today announced the release of an
updated modeling tool that will allow the public to test water management
scenarios and compare their outcomes. The tool, known as the Delaware River
Basin-Planning Support Tool (DRB-PST), provides interested stakeholders with
the ability to test flow management scenarios against a set of existing
targets, regulations, and laws that govern the use of water within the Delaware
River Basin.
The tool will show users how those scenarios would change an array
of outcomes, including the amount of water available for drinking supplies,
downstream releases, habitat protection, flood mitigation, and more.
“The
availability of the DRB-PST modeling tool is a positive development intended to
support a more comprehensive understanding about how reservoir and flow
management operating plans affect river flows and related aquatic habitats,”
said DRBC Executive
Director Steve Tambini. “It will allow interested stakeholders
to use a science-based tool to compare the impacts of ‘what-if’ scenarios on
multiple and complex water resource goals, targets and objectives.”
River
flows, diversions out of the basin, and water uses within the basin are
managed, operated and regulated through a series of complex and interdependent
rules and targets. The DRB-PST model uses hydrologic inputs (like runoff and
snowmelt), operating conditions, and management rules to help evaluate the
impacts of reservoir operating plans on the multipurpose water resource
objectives identified in the Delaware River Basin Compact, which created the
DRBC in 1961.
Three
reservoirs located in headwaters of the Delaware River that are owned and
operated by the City of New York (NYC) provide about half of the city’s water
supply. Downstream releases of water from these reservoirs and diversions out
of the basin for NYC and New Jersey were established and continue to be
negotiated by Delaware, New Jersey, New York, Pennsylvania, and NYC (commonly
known as “the Decree Parties”) under the terms of a 1954 U.S. Supreme Court
Decree and the subsequent Good Faith Agreement Recommendations.
The
DRBC and the Decree Parties have some overlapping membership and a long history
of collaboration on planning and modeling issues within the Delaware River
Basin. The DRBC signatory members include the four basin states and the federal
government. NYC is not a DRBC member. The Compact prohibits the DRBC from
adversely affecting the releases or diversions provided in the 1954 Decree
without the unanimous consent of the five Decree Parties.
The
Flexible Flow Management Program (FFMP), which has been unanimously approved by
the Decree Parties, is intended to meet water supply demands, protect fisheries
habitat downstream of the NYC-Delaware Basin reservoirs, enhance flood
mitigation, and repel the upstream movement of salt water in the Delaware
Estuary. The FFMP’s target numbers and goals are included in the PST-DRB model
and any changes to the FFMP in the future can be reflected in the model as
well.
The
DRBC’s original water supply planning model was developed in 1981. That model
was revised several times to include additional data, facilities, and flow
management policies, and was moved into OASIS software in the early 2000s. The
original OASIS model known as DRB-OASIS can simulate the current FFMP,
including the Combined Seasonal Storage Objective (CSSO) for flood mitigation,
but not the revised Habitat Protection Program (HPP) which has evolved since
the first FFMP.
The Habitat Protection Program uses simulated forecasts of
reservoir inflows to determine the amount of water available for fisheries
releases from the three NYC reservoirs. In doing so, modeling can be performed
to evaluate scenarios that use water more efficiently for fisheries habitat
objectives while maintaining the reliability of critical water supply
objectives and flood mitigation components of the FFMP.
The
DRB-PST incorporates aspects of NYC’s Operations Support Tool (OST), a
sophisticated monitoring and modeling system that allows for better predictions
than previous tools of reservoir-specific water storage levels, quality, and
inflows. OST uses forecasts to determine the amount of available water to
release for habitat protection and assesses the risks of reservoir operations
to public water supply needs across the entire NYC reservoir system, not only
its three Delaware River Basin reservoirs. DRB-PST incorporates the OST
simulated forecasts for long-term water supply planning based on reservoir
operations.
A technical working group from DRBC, the Decree Parties (four
states and NYC), and the City of Philadelphia have worked together to ensure
that the model is useful for those with an interest in Delaware River
operations. This group will continue to evaluate and verify model inputs and
results and release revised PST versions as necessary.
“Scientists
and engineers from DRBC and New York City collaborated to ensure this new
public modeling tool produced accurate results that are comparable to those
generated by the OST modeling tool that the City uses to make decisions about
reservoir operations every day,” said Tambini.
Persons
who did not previously use the DRB-OASIS model who wish to obtain the DRB-PST
model for the first time will need to purchase required software. Additional
information about DRB-PST and the upcoming Regulated Flow Advisory Committee
meeting can be found on the commission’s web site at www.drbc.net.
DRBC
is a federal/interstate government agency responsible for managing the water
resources within the 13,539 square-mile Delaware River Basin without regard to
political boundaries. The five commission members are the governors of the
basin states and the commander of the U.S. Army Corps of Engineers’ North
Atlantic Division, who represents the federal government.
More information
concerning the 1954 Decree, the Decree Parties, and related water management activities
can be found on the web site for the USGS Office of the Delaware River Master
at http://water.usgs.gov/osw/odrm/.