INFLUENCE OF URBANIZATION ON WATER QUALITY: A TALE OF TWO CITIES

The influence of urban growth on water quality will continue to be a major problem through this century as urban centers are anticipated to increase in size and population. We have obtained a series of river water samples from two rapidly expanding urban areas in the USA: Atlanta, Georgia and Columbus, Ohio. Samples were analyzed for their major element, fixed nitrogen and dissolved organic carbon (DOC) concentrations. Samples were taken seasonally at both locations in portions of the river above the urban regions, within the urban regions and below the urban regions. In the case of the Chattahoochie River, Georgia, Cl^-, Na ⁺, SO₄^2-, NO₃^- and DOC increase dramatically as the river flows through the metro Atlanta area. This increase is as much as 15, 7, 6, 6.5 and 2.5, respectively, above "background" concentrations. In the Scioto River, Ohio, the only observed increase is that of NO₃^-, whose mean increase was 5 times above the upstream values. Other solutes are apparently diluted in the Scioto River by tributary water input, or little urban input may occur. The Chattahoochie downstream enrichments are similar to those observed for the Seine River as it passes through metro Paris. The population stresses on the Chattahoochie and the Scioto Rivers are similar, yet the Chattahoochie appears to show greater impact through urban contact. The reason for this is unclear, but may in part be due to higher background in the Scioto watershed concentrations resulting from upstream agricultural inputs in the Scioto watershed which mask any urban input from metro Columbus.