Meeting Thursday on F.E. Walter Dam

But the study isn't going to change its primary purposes -- flood mitigation and recreational use.

Those purposes were defined by Congress, and it would take another act to change those uses. No one is interested in that.

The dam was constructed in 1961 by the U.S. Army Corps of Engineers in response to flooding in the Lehigh Valley after Hurricane Alice inundated communities in the river's watershed and repeated flooding in the past.

Once it was built, the opportunities provided by releases from the dam gave birth to a vibrant recreational use of the reservoir and river: whitewater rafting and all sorts of boating, as well as fishing and hunting provide serious dollars to the watershed communities.

Caprioli, from USACE, explained that the study could well increase recreational opportunities.

Shallcross, from DRBC, pointed out that the meeting is an opportunity to hear from all stakeholders. The study might suggest improvements to releases for whitewater rafting or improvements to the cold-water fisheries.

"It's important that we gather input early," said Shallcross. "This is a pivotal reservoir in the Lehigh Valley and for the whole watershed. We want to manage it as effectively as possible,"

But, again, why is New York City involved? The answer to that lies in the point of the study.

Really, it's all about the water supply for the whole watershed.

When the three Delaware River reservoirs were being built by New York City in the late 1950s/early 1960s, New Jersey was a little worried that NYC would soak up too much water from the river, leaving little for New Jersey. (There are four states interested in Delaware water, so it does get complicated.)

States' disputes are handled by the U.S. Supreme Court and that court issued a decision and all parties to the dispute had to sign on. In this case, that meant New York City, New Jersey, New York, Pennsylvania, and Delaware.

A main stipulation of the decision was that New York City had to maintain a certain flow at the Montague (New Jersey) gauge, thus insuring that New York can't take "too much" of the river's waters.

Shallcross explained -- if all signatory parties agree -- the flow rate can be changed; an example is in times of serious drought.  The basin-wide drought management plan, agreed to by the five parties and incorporated into DRBC’s Water Code, calls for reductions in the Montague flow target to help conserve water.

One of the biggest concerns for those three flow managers is how the ocean and its salt waters can affect municipalities that take water from the river. That ocean water washes in and out with the tide but also pushes north, pushing salty water into the estuary and the river.

If that salt water gets pushed too far, it can interfere with the supply of the drinking water that municipalities like Philadelphia get from the river. Basically, municipal water-supply systems can't handle salty water.

So there has to be enough fresh water coming south to push that salt front away.

The idea of using F.E. Walters water to help in that push has been, according to Shallcross, "kicking around for years."

What's creating a sense of urgency are the changes expected from sea-level rise -- more water moving with more force upriver -- and climate change -- maybe more water will come south, maybe less. All the modeling suggests that there will be changes.

"We have to plan for the future," said Adam Bosch, director of public affairs, NYC Environmental Protection. "We don't want to get caught flat-footed. Then people would want to know why we didn't look ahead at how we use our water resources."

"We have to be proactive," he said.

Here's a timeline of what's happening when for this study: