Routine water-quality tests show four Jackson County creeks exceed state bacteria standards and contamination has already climbed to levels not typically seen until August.
The Mail Tribune reports (http://bit.ly/1nN71Qi) the E. coli could pose an elevated risk of illness and infection for swimmers or waders.
The Rogue Valley Council of Governments' Natural Resource Department reported the high levels in Neil Creek, Bear Creek, Griffin Creek and Jackson Creek.
Specialists say recent warm temperatures and drought conditions likely will mean the unfavorable levels continue all summer.
Officials say waste from pets, livestock and wild animals, leaking septic systems and illegal dumping from portable toilets or recreational vehicles are all possible sources for the bacteria.