Flow Exceedence Charts

These charts were derived from the output of Oasis simulations over the entire period of record, 1928 to 2000, with New York City diversions set to 500 MGD. That level of diversions, 500 MGD, is our best estimate of what diversions are likely to be over the next few years. The Coalition has been strongly urging everyone involved to make decisions based on what is likely to happen on the River in the coming years, as well as on worst-case scenarios. The standard worst-case scenario being employed by the DRBC is 765 MGD.

So, what should we see in these charts? Policy CP 2 is designed specifically to guarantee that minimum flows in the tributaries and Mainstem, will be adequate during the summer. As long as reservoir storage (in the entire system as well as at individual reservoir levels) stays in the L-2 level, using Cannonsville as an example, releases under CP 2 will be 350 CFS. If storage drops to the L-3 level the releases under CP 2 drop to 165 CFS.. Of course, that will happen in those summers when the system is heading into drought conditions.

The charts clearly shows that CP 2 meets higher flow objectives on all branches and on the Main stem. Looking at West Branch Delaware, its flows exceeds 250 CFS 98.5 % of the time, exceeds 350 CFS 97.8 % of the time, and exceeds 450 CFS 54.4 % of the time – and this includes summers in drought, includes even the drought of record in the 1960s. Neither Montague target, nor PPL manipulations impact this. These simulations included the current (so-called new) PPL rules.

So, here is the conclusion. If you are trying to protect the fishery against low summer flows, CP2 does that job. Its trout and shad habitat benefits come from this ‘low flow’ protection and are substantial.

Flow Excedence charts - Daliy Flows in Summer. Click individual chart to enlarge

Morever, 350 CFS level on the West Branch Delaware was arrived at after considerable study in order to have a benefit in the upper main stem. The DSS habitat numbers. that are incorporated in our March 6 presentation testify to the fact that it is so.

We believe that we have done exactly what the fishing community has been arguing for -- for so many years. Under adaptive release we will never again see a 45 CFS release from Cannonsville while the reservoir stands at 90% capacity – just because the banks have been exhausted. The banks are gone -- thanks to our work, and our numbers. The yo-yoing of flows from very low to very high also can not happen because of the 350 CFS L-2 guarantee. It still can be some yo-yoing above 350 because of the way the River Master tries to hit the Montague target on a daily basis. We continue to argue that they modify this to weekly average -- the jury is still out on whether they will listen to us on this issue.

The stakes are enormous. Failure of the fishing community to support CP 2 invites the Decree Parties and the DRBC to stick with the inferior THPMDP – or worse go back to Rev 1.