Published On: Fri, Oct 12th, 2018

Reservoirs upstream of the Delaware River are at capacity. Time to worry?

Geese seek shelter during one of the many Delaware River floods.

With two of the three New York City drinking water reservoirs upstream of the Delaware River at or over capacity, should those of us living and working near the waterway in New Hope and Lambertville be concerned about the kind of catastrophic flooding seen in 2004-06?

Coming off a very wet summer, the Pepacton reservoir is currently at 100% of capacity, while the Neversink is at 102%. A third contributing reservoir, the Cannonsville, was at 94.8% on Friday. There are more than a few local residents who believe that a sudden release of water from these reservoirs was a significant factor in the string of historic floods that occurred more than 12 years ago.

But officials are saying it’s different this time.

“It certainly has been a wet summer,” observed Raymond Kruzdlo, Senior Service Hydrologist at the Mount Holly Weather Forecast Office of the National Weather Service. “But the reason we had such catastrophic floods [in 2004-06] was because it was wet for so many years before that.”

New York City’s Water Supply System (Source: NYC Department of Environmental Protection)

Kruzdlo said that the decade of heavier-than-usual rainfall that preceded the historic floods along the Delaware River provided the kind of deep, long-term saturation that can become a significant factor in catastrophic flooding. That type of “deep” saturation, along with the amount and exact location of rainfall, are far bigger factors than the amount of water in upstream reservoirs.

“People think an empty reservoir will solve all the problems,” said Kruzdlo. “I don’t think it will. Does an empty reservoir help? I don’t know to what extent it would help if half the reservoirs are full or empty. The Delaware River Basin is so large, those reservoirs are not capturing a large amount of the basin.”

“Whether you have the reservoirs or not, the water is still going to come down,” Kruzdlo added.

On Friday afternoon, water levels on the Delaware River at the New Hope-Lambertville Bridge were at around five feet, according to the National Weather Service. Flood stage is 13 feet.

Kruzdlo noted that New York reservoir capacities are monitored by those watching Delaware River levels.

“Forecasters are taking reservoir flows into account in their projections,” he said. “Things have changed since the ’04-06 floods.”

Delaware River Basin Commission (DRBC) spokesperson Peter Eschbach agreed.

“20o4-06 was a ‘perfect storm’ situation, with saturation and rain that blanketed the northern part of basin,” he recalled. “When that comes together, there’s not a whole lot you can do.”

Delaware River Basin (Source: DRBC)

Formed by Presidential decree in 1961, the DRBC consists of representatives from Delaware, New Jersey, Pennsylvania, and New York that work together as equal partners in a river basin planning, development, and regulatory agency.

Eschbach said that the degree of communication and coordination among those monitoring Delaware river water levels precludes the chance of a sudden, uncoordinated release of water by New York reservoirs.

“There a vary active group of decree parties meeting to discuss and watch that,” he explained.

According to the DRBC, the Delaware River is fed by 216 tributaries, the largest being the Schuylkill and Lehigh Rivers in Pennsylvania. The Lehigh has a significant impact on water levels on the Delaware River near New Hope.

“You’ve got to look at the basin as an entire system,” observed Eschbach.”New York is just one area in the basin — what’s the weather over in Pennsylvania at the Lehigh watershed?”

“The actual impact of reservoirs on flooding in the main stem Delaware is minimal compared to other factors,” he added. “By themselves, there should not be cause for concern.”

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  1. origin11@comcast.net' JaneAdele says:

    Snow pack and snow melt have to be factored in also. If we have a wetter than normal winter, the Delaware Basin could be at, or beyond, capacity.

  2. The DRBC’s own report showed a 20% void would have resulted in 3-4 feet less water in Lambertville, which means we would have dodged a bullet in 3 of the past 6 flooding events

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