Public health perspectives of channelized and unchannelized headwater streams in central Ohio: a case study.

Headwater streams constitute the majority of watersheds in the United States and many in the midwest have been channelized for agricultural drainage. Public health implications of water chemistry and aquatic insects within channelized and unchannelized headwater streams have not been explored. We sampled water chemistry and aquatic insects in two channelized and two unchannelized headwater streams in central Ohio from December 2005 until November 2008. Maximum concentrations of ammonium, nitrate plus nitrite, and chlorothalonil were greater in channelized streams. Nitrate plus nitrite and atrazine also exceeded drinking water standards more often in channelized streams. Maximum concentrations of simazine and the percentage of times it exceeded the drinking water standards were greater in unchannelized streams. The predicted hazard potential of nutrient and pesticide mixtures was greater in channelized streams. Mosquito abundance did not differ between stream types. Chironomid abundance was greater in channelized streams. Biting dipterans did not exhibit consistent abundance trends and only differed between stream types in the summer and fall. Our results suggest that if whole stream uptake of nutrients and pesticides is minimal in channelized headwater streams then nutrient and pesticide inputs from these streams may impact downstream drinking water sources. Our results also suggest channelized and unchannelized headwater streams are not serving as a significant source of mosquitoes.