Record runoff discharging at Conowingo Dam
Flood warnings remain in effect in Harford and Cecil counties today as record rain and snowmelt in Pennsylvania and New York send high water down the Susquehanna River. The river has already passed flood stage at Marietta, Pa., about 35 miles upstream from Conowingo. It appears to have crested at Harrisburg.
UPDATED: The water below the Exelon Power Corp.'s Conowingo Hydroelectric Station is forecast to reach 25.5 feet by this evening, then begin to fall. At 10:30 a.m. it was at 24.5 feet. That is a foot above flood stage (23.5 feet). Minor flooding is occurring, according to the National Weather Service; "moderate" flooding is expected.
The forecast, if realized, would bring the river to Notification Level 5, with 21 to 25 of the dam's 53 gates open. At Level 5, backyards and basements on Main Street, and Tome's landing in Port Deposit begin to flood.
An earlier NWS forecast had predicted the river level would reach Level 6. An earlier version of this post indicated that level had already been reached. It has not. Your weather blogger regrets the error. Here's more on the Notification levels..
The webcam photo was taken in June 2006, during runoff from heavy rains. If anyone snaps some pictures there today, send them along and we'll post them.
Water was rushing through the dam this morning at a rate of 323,000 cubic feet per second. The previous record for a March 6 was 320,000 cf/s in 1979. The average for this date is 70,500 cubic feet per second. The all-time record high flow was 1.13 million cubic feet per second, on June 24, 1972, in the aftermath of Tropical Storm Agnes.
Below is a graph of the discharge rate at 9:30 this morning. You can get real-time data on the discharge by clicking here.
Comments
"...At Level 5, backyards and basements on Main Street, and Tome's landing begin to flood."
Main Street where?
FR: Port Deposit
Posted by: Eve | March 6, 2008 1:36 PM
Why is there a record now? Did they add new flood gates? Or is there something else going on? I don't think the overall precipitation has been that high recently. Certainly not as high as when Isabel came to town? But then I may be thinking of just Baltimore. The watershed for the Susquehanna reaches far into upstate NY. Any ideas?
FR: It's only a daily record - the highest discharge rate for a March 6 in the 40 years they's been keeping track. That's not a very long period, so new daily records will be more common than, say, in Baltimore, where weather records go back to the 1870s.
Posted by: Peter Wayner | March 7, 2008 6:42 AM
when will they start to run water normaly because fishing is real bad at the dam and down river and as i can see more and more fish are dieing i guess due to warm and old areas of water
Posted by: vic | August 24, 2008 11:47 AM
Vic: This entry was posted in March 2008. I have no idea why the fishing is bad now. Die-offs are likely due to oxygen depletion due to algae blooms and widening dead zones in the bay this summer. There was a bloom in the Inner Harbor a week or so ago. Turned a nice shade of green.
Posted by: frank roylance | August 24, 2008 12:11 PM