Thirty sites with an urban intensity index of 0 to 100 were sampled for water chemistry as part of the NAWQA EUSE Study. Sample analysis included nutrients, chloride, sulfate, sediment, field parameters, organic carbon and a suite of commonly used agricultural and urban pesticides. Ten sites that were representative of the range of the UII were sampled bi-monthly during the 2004 water year, the remaining 20 sites were sampled twice; once during the spring and all sites were sampled during the ecological data collection in late summer 2004. All samples were collected following protocols outlined in the USGS National Field Manual, Techniques of Water Resources Investigations, Book 9, Handbook for Water-Resources Investigations. Results of the chemistry sampling can be found on the Maps and Data page.
The Hydrology section discussed how flow changes resulting from development may effect fish and stream ecology.
The Water Chemistry
Possibly it is not the flow but rather contaminants within the water that is affecting the fish population. Some of our preliminary data indicates that polycyclic aromatic hydrocarbons (PAHs) increase steadily with urbanization. (jjs)
Note that concentrations of PAH seem to especially increase after the urbanization index reaches 50. PAHs are a family of compounds (such as phenanthrene, flouranthene, benzo[a]pyrene) that may potentially harm the base of the stream food chain (benthic community) or be carcinogenic to humans. The graph does not show a clear relationship (some scatter) between urbanization and PAHs; however our Study is currently examining factors which may affect the relation. For example, site "A" has a higher PAH level than would seem to be justified by its urbanization level. There is a superfund site within the area that drains to stream "A" and may be affecting the stream PAH concentration. Information such as this will help us better understand the above relationship between urbanization and PAHs. (jjs)