Pittsburgh's rivers often freeze in the winter, followed by flooding from snowmelt in the spring thaw. A century ago the rivers often feel so low in summer droughts that navigation was impossible, so the Army Corps of Engineers constructed a series of locks and dams that divide the the river into a series of "pools." The Pittsburgh pool, also called the Emsworth pool, extends twenty-four total miles, from the Emsworth Dam on the Ohio river, six miles below downtown Pittsburgh, to points seven miles up the Allegheny to the Highland Park Lock and Dam and eleven miles up the Monongahela to the Braddock Lock and Dam.
A no-wake zone is in effect on the rivers right around downtown Pittsburgh on weekends from May 1 to October 1 from 3:00 p.m. Friday until midnight Sunday, as well as for Memorial Day, July 4, and Labor Day. According to the Pennsylvania Fish & Boat Commission "boats are limited to slow, no wake speed from the Fort Pitt Bridge over the Monongahela River and the 9th Street Bridge over the Allegheny River to the West End Bridge over the Ohio River."
River Water AdvisoriesThe Allegheny County Health Department generally issues river water advisories from the middle of May through the end of September. The advisories indicate whether water quality in rivers and streams is normal, or a combined sewer overflow (CSO) alert has been issued. Alerts are issued when significant rainfall causes sewers carrying a combination of sewage and storm water to overflow and contaminate rivers and streams. A CSO alert does not prohibit recreational activity, but rather cautions people to minimize water contact during outings. Those with weakened immune systems and open cuts or sores are more vulnerable to infection from exposure to contaminated water.
When an alert is in effect, marinas, docks and other sites along the rivers fly orange-colored flags with "CSO" printed in black. Boaters can also get updates by calling the advisory hotline at 412-687-ACHD (2243), visiting the Allegheny Health Department website, or subscribing for text alerts.