Spring Grove Weir Removal

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Pennsylvania Water Science Center personnel remove broad-crested weir, Codorus Creek at Spring Grove

The weir removal was completed Summer 2021, in collaboration with U.S. Army Corps of Engineers. 

The station was established in 1966 to measure gage height and discharge relative to upstream reservoirs. Although low-head dams and weirs appear innocuous, they create dangerous conditions for water recreation. Headwater behind the weir displays smooth and laminar subcritical flow conditions. As water crests and cascades over the structure, flow becomes supercritical, dramatically increasing in velocity and generating a hydraulic jump. At the downstream base of a low-head weir this produces strong recirculating backwater that can be impossible to escape, even for experienced swimmers or those wearing a personal flotation device. Weir removal ensures public safety while improving upstream hydrologic connectivity for aquatic biota.

The stilling well for water levels was updated with a pressure transducer to provide near-real-time stream discharge (flow) data, transmitted to NWIS Web every 15 minutes.

before
after
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Before & after broad-crested weir removal from USGS Station 01574500 Codorus Creek at Spring Grove, Pennsylvania. 

Cameron Ensor and Nick Grim demolish a broad-crested weir

North Atlantic-Appalachian Region Photo Contest Winner | July 2021 | USGS at Work
Certified USGS Heavy Equipment Operators Cameron Ensor and Nick Grim demolish a broad-crested weir at USGS Station 01574500 Cordorus Creek at Spring Grove, Pennsylvania.   (Pennsylvania Water Science Center, public domain)