DRBC takes the lead on the drought operating program regulating river flows and reservoir releases. Drought conditions are based upon storage available in several basin reservoirs. DRBC drought operating plans are implemented either basinwide or for the lower basin. DRBC's drought operations complement the plans of the states, which respond to local water supply conditions, for example, precipitation, groundwater levels, soil moisture, and streamflow.

During drought conditions, the DRBC has several objectives:

• Preserve Reservoir Storage
• Manage the Salt Line
• Complement State Drought Management Programs

An Overview of Drought in the Delaware River Basin (pdf)

The DRBC basinwide drought operating plan is triggered by declining storage in three New York City reservoirs (Cannonsville, Pepacton, and Neversink) at the headwaters of the Delaware River.

A storage-based rule curve was developed with trigger points for Drought Watch, Drought Warning, and Drought Emergency. As water levels in the reservoirs decline, there is an agreed upon plan of water use reductions in order to conserve reservoir storage. The drought operating plan includes reductions to NYC's water supply diversion and in the established flow targets at Montague and Trenton, N.J.

Reductions tied to Drought Warning and Drought Watch are implemented as soon as the triggers are crossed; they do not require additional resolutions or DRBC action.

Pursuant to section 3.3 of the Delaware River Basin Compact (pdf), the commission may declare a state of emergency resulting from a drought by unanimous consent of all members or under section 10.4 of the Compact declare a water supply emergency after holding a public hearing. These provisions provide the DRBC with additional authority to call for storage and releases from private, state and federally owned reservoirs. Under this additional authority, DRBC can manage an additional 69 billion gallons of storage (view map; pdf).

During the last major basinwide drought in 2001-2002, 500 million gallons of water was conserved per day through DRBC's basinwide drought operating plan, helping reduce uncertainty in the management of water supply during periods of drought.

There are times when hydrologic conditions and reservoir storage are "normal" in the upper basin, but the lower basin may be experiencing drought conditions. When this occurs, the upper basin is operated normally while the lower basin drought operating plan is triggered.

Just as there is minimum flow objective of 1,750 cubic feet per second (cfs) at Montague, N.J., the DRBC Water Code sets a minimum flow objective of 3,000 cfs at Trenton, N.J. (head of tide).

Why is there a Trenton flow target? The DRBC lower basin drought management plan focuses on controlling the upstream migration of salty water (referred to as the “salt front” or "salt line") from the Atlantic Ocean through the Delaware Bay into the tidal river. The salt front's location fluctuates along the tidal Delaware River as freshwater streamflows traveling downstream increase or decrease in response to hydrologic conditions, diluting or concentrating chlorides in the river. DRBC-directed releases from Blue Marsh Reservoir (located on the Tulpehocken Creek, a tributary of the Schuylkill River) and Beltzville Reservoir (located on the Pohopoco Creek, a tributary of the Lehigh River) to meet the Trenton flow target are used to help repel, or flush back, the salt-laced water in order to protect the drinking water intakes in the downstream urban areas of Philadelphia and Camden. Water supply storage in these two lower basin reservoirs, both owned by the U.S. Army Corps of Engineers, is financed by surface water users under a water charging program implemented by the DRBC.

Storage in Blue Marsh and Beltzville reservoirs is used to trigger drought warning and drought operations in the Lower Delaware River Basin - that portion of the basin downstream of Montague, N.J. This allows for reductions in the Trenton flow target and the New Jersey diversion when lower basin conditions are drier than in the upper part of the basin. Accordingly, lower basin operations are controlled by both basinwide or lower basin storage triggers, with the most limiting restrictions controlling.

Merrill Creek Reservoir, a pumped storage facility located near Phillipsburg in Warren County, N.J., releases water to replace evaporative water losses ("consumptive use") caused by power generation when the basin is under DRBC-declared drought operations. Releases are made during both basinwide and lower basin drought warnings and droughts whenever the flow at Trenton drops below 3,000 cfs for at least five consecutive days.