Swimming in Alum Creek Reservoir or the Delaware Reservoir could be dangerous for the elderly, children and those with weak immune systems, the state warned Friday. The Ohio Department of Natural Resources issued bacteria contamination advisories for the reservoirs Friday afternoon.adcelannotate = {"mobilepaywallcategory" : "MOBILE_PREM-LOCAL","nativepaywallcategory" : "NATIVE_PREM-LOCAL"};