Sunday, June 25, 2006

The river at Riegelsville is leveling off at about 4.20', which is a bit above the mean daily flow. It's muggy, depressingly dark and more rain is forecast for today, possibly heavy, but overall this has been a beneficial weather system that is helping restore soil moisture and the base flow of the tributaries, which have all been running low this spring. Most of the tributaries have only seen moderate increases in flow, although the Tohickon Creek shot up from 1.5' to 4.5' yesterday, but it has since fallen back to around 2.00' this morning.

Dee Keller of Keller's Landing in Upper Black Eddy called to ask about a six inch spike in the Delaware on June 19 (overnight). A few minutes of tracing stream gauges from Riegelsville and upriver revealed that the Lehigh River and its tributaries had an even bigger spike. Dee observed that water clarity diminshed overnight. That was due to the intense storm cell that dumped over 2 inches of rain on all those Lehigh Valley corn fields, construction sites and city streets. The Lehigh is the single greatest source of pollution to the non-tidal Delaware River, and that can be seen in the form of algal growth on the river bottom. One can easily observe the difference above and below the Lehigh confluence. The Lehigh is also the second largest tributary to the Delaware with a watershed that is slightly smaller than the Schuylkill River, the largerst trib, which runs into the Delaware in southwest Philly.

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