While not at pretty as NOAA, USGS river data has a lot more flexibility in data retrieval and includes more metrics. They also document their services for automatic retrieval.
NOAA has the prettier site, and the advantage of including prediction data. The downside is that, while they have xml feeds of data, such as this for NRSP1, there’s zero documentation on their service.
Documentation on various web services about water from the USGS who has been doing lots in the last year or so to make this sort of data more accessible.
The Corps of Engineers Philadelphia District helps manage the flow of rivers in the Delaware Basin, including the Schuylkill, which primarily controlled by the damn at Blue Marsh Lake.
Most people are unaware of the extent to which our government agencies, USGS, NOAA and the Army Corps of Engineers monitor river and stream flow. Most of the measurement is via automated stream gauges. The agencies share the data and do a good job of making it available, as seen in the links above. Unfortunately I’ve managed to learn a lot about stream gauges and stream flow data. As it turns out, my apartment happens to be on a river. I didn’t think about that much when I moved in. The river looked just calm and provided a nice view. And 364 days a year, that’s all there is to it. Once and a while, it gets more complicated. This is what it looked like in March 2011, when the Norristown stream gauge on the Schuykill River was at 14.32 feet. Normally it’s closer to 7 or 8 feet deep. I don’t have pictures of when it was at 19.13 feet in June 2006. The local authorities kind of didn’t want folks to stick around for that.