Location: Soil Drainage Research
Title: Public Health Perspectives of Channelized and Unchannelized Headwater Streams in Central Ohio: A Case Study Authors
Submitted to: Journal of Water and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 3, 2010
Publication Date: April 7, 2010
Citation: Smiley, P.C., King, K.W., Fausey, N.R. 2010. Public Health Perspectives of Channelized and Unchannelized Headwater Streams in Central Ohio: A Case Study. Journal of Water and Health. 8:577-592. Interpretive Summary: Channelized headwater streams or agricultural drainage ditches are a common landscape feature in the midwestern United States. Management of these modified streams focuses on drainage without regard for downstream impacts and their potential to serve as a source of macroinvertebrate disease vectors. Others have compared the ecological health between channelized and unchannelized headwater streams, but the public health implications have not been explored. We evaluated the public health risks posed by channelized headwater streams by comparing nutrients, pesticides, and abundances of potential macroinvertebate disease vectors between channelized and unchannelized headwater streams within central Ohio. We found that concentrations of commonly occurring nutrients and pesticides was often greater in channelized headwater streams and exceeded national drinking water standards more often. We also observed potential macroinvertebrate vectors of the West Nile virus, Lacrosse encephalitis, St. Louis encephalitis, and Eastern Equine encephalitis constituted a small fraction of the overall macroinvertebrate captures and abundances did not differ between stream types. Our results suggest that management of channelized headwater streams may be necessary to reduce the public health risks related to the downstream transport of agricultural nutrients and pesticides. Specifically, agricultural conservation practices capable of reducing nutrient and pesticide loads within channelized headwater streams may assist with the protection of downstream surface drinking water sources. Our results also suggest headwater streams in general may not serve as a significant source of potential disease vectors and insecticide application and channelizing these streams for larval mosquito control does not appear to be warranted.
Technical Abstract: Headwater streams constitute the majority of watersheds in the United States and many headwater streams in the midwest have been channelized for agricultural drainage. Public health implications of water chemistry and aquatic macroinvertebrates within channelized and unchannelized headwater streams have not been explored. We sampled water chemistry and aquatic macroinvertebrates in two channelized and two unchannelized headwater streams in central Ohio from December 2005 until November 2008. In general, maximum concentrations of ammonium, nitrate plus nitrite, and chlorothalonil were greater in channelized than unchannelized streams and maximum concentrations of simazine were greater in unchannelized streams. We developed a water quality index to predict the toxicity of the nutrient and pesticide mixtures based on national drinking water standards and observed predicted toxicity was greater in channelized than unchannelized streams. Mosquito abundance did not differ between stream types and chironomid abundance was greater in channelized than unchannelized streams. Biting dipterans did not exhibit consistent abundance trends between stream types. Our results suggest that if minimal nutrient and pesticide uptake occurs within channelized headwater streams then nutrient and pesticide inputs from these streams may impact downstream drinking water sources. Our results also suggest channelized headwater streams do not represent a greater public health risk than unchannelized streams and neither stream type is a significant source of mosquitos.