With projections of increased precipitation in Ohio because of climate change, the number of combined sewer overflows (CSOs) is likely to increase.Person in the Rain  Presently (2011), Ohio has 81 communities with CSOs and 1,233 permitted overflow points.  More important than the predicted overall increases in precipitation for winter and spring is the increase in precipitation intensity throughout the year.  For example, if it rains two inches in a one hour period, which is likely to occur more frequently, versus two inches over a 24-hour period, Ohio’s combined sewer system are likely to have their capacities exceeded more frequently, meaning more CSOs.

The US Environmental Protection Agency projects that between 2060 and 2099, CSOs in the Great Lakes region could increase, on average, 13 to 70 percent from present levels as a result of climate change.  Future growth of cities and population could also create more impervious surfaces and reduce green space, resulting in increased run off and potentially exacerbating the impact of more, and more intense, precipitation on CSOs.  Bottom line, more precipitation is likely to cause more CSOs, which means more pollution in Ohio’s waterways and greater threats to public health.


View current Ohio CSOs (OEPA, 2013)

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