1 Potential Effect of Climate Change on Design-Period Low Flows in the Mid-Atlantic US Mary E. Schoen 1 , Mitchell Small 2 , Michael L. DeKay 3 , Elizabeth Casman 4 , Chuck Kroll 5 CE Database subject headings: Water Quality, Low Flow, TMDL, Precipitation, Temperature Abstract This study examines the relationship between changes in precipitation and temperature and the properties of low streamflow to estimate the potential impact of climate change on design-period low flows and associated Total Maximum Daily Loads (TMDLs) of primary pollutants. Stepwise linear regression is used for predicting the future low-flow statistic 10 , 7 Q using the physiographic and climatic characteristics of 160 watersheds in the Mid-Atlantic region of the United States. Based on four general circulation models’ (GCMs’) climate predictions of future increases in temperature and variable changes in precipitation, model results show a decrease in the 10 , 7 Q over the 21st century. Using Latin Hypercube sampling of parameter estimates, the fractional change in low flow and the resulting change in TMDL of a point-source primary pollutant are estimated for GCM 1 PhD Candidate, Engineering and Public Policy, Carnegie Mellon Univ., 129 Baker Hall, Frew Street , Pittsburgh, Pa 15213. E-mail: mschoen@andrew.cmu.edu 2 H. John Heinz III Professor of Environmental Engineering, Carnegie Mellon Univ., Civil & Environmental Engineering and Engineering & Public Policy, Porter Hall 119, Frew Street Pittsburgh, PA 15213. E-mail: ms35@andrew.cmu.edu 3 Associate Professor, Engineering and Public Policy, Carnegie Mellon Univ., Hamburg Hall 2107B, Forbes Ave., Pittsburgh, Pa 15213. E-mail: dekay@andrew.cmu.edu 4 Associate Research Professor, Engineering and Public Policy, Carnegie Mellon Univ., 129 Baker Hall, Frew Street , Pittsburgh, Pa 15213. E-mail: casman@andrew.cmu.edu 5 Associate Professor, Environmental Resources and Forest Engineering, SUNY College of Environmental Science and Forestry, Syracuse, NY 13210. E-mail: cnkroll@esf.edu