Hydrologic Evidence of Climate Change in Monroe County, New York

Abstract

The long-term annual mean air-temperature record from the National Weather Service station at the Rochester, N.Y., airport indicates an apparent increase over the past 4 decades; however, this increase does not differ substantially from the historical range of temperatures during the last century. Annual precipitation totals are increasing, and this increase is reflected in the peak flows of streams in urbanized basins and in the base flows and 7-day low flows of two rural, unregulated streams— Oatka and Black Creeks—in Monroe County, N.Y. The magnitudes of recent peak flows, since about 1997, appear to be comparable to those of earlier peaks, but the frequency of peak flows appears to be increasing, at least in the urbanized basins. Base flows and 7-day low flows are increasing as expected from the increasing amounts of precipitation, yet 7-day high flows show no discernible trends. In contrast, streamflow in the urbanized Allen Creek Basin, the hydrology of which is affected by its large amount of impervious area, shows downward trends in base flow and in 7-day low flows, and an upward trend in 7-day high flows. These differences between the urban and rural streams persist even when coincident periods of record are used in the analysis. Flow conditions in the Genesee River are unique because the regulation of outflow from Mount Morris Lake has decreased the number and magnitude of damaging floods downstream in the Rochester area and also has diminished the 7-day low and high flows in that reach.