42 Applied Hydrogeology and Environmental Geology for the 21st Century (Posters)

BASEFLOW GENERATION AND LOSS IN THE LITTLE CHAZY RIVER WATERSHED, NORTHEASTERN NEW YORK

Paper number: 42-15
Program: THEME SESSIONS
Time: 8:00 AM – 12:00 PM

Authors

Abstract

In this study, we examine the spatial pattern of baseflow discharge and its relationship to watershed geology, physiography, soils and land cover in the Little Chazy River watershed in northeastern New York. The Little Chazy River (watershed area = 142 km2) originates in upland forests on the northeastern foothills of the Adirondack Mountains and flows eastward across the Champlain Lowland, discharging into Lake Champlain. The uplands are characterized by moderate relief (~280m local relief) and thin soils with extensive areas of exposed sandstone bedrock at Altona Flat Rock. The Champlain Lowland is characterized by low relief (<180m local relief) with deep soils developed on glacial, marine and lacustrine soils. For this study, stream discharge and water temperature were measured at the outlets of 15 gauged subwatersheds that range in area from 0.6 km2 to 19 km2. Water temperature was also monitored at five ungauged locations on the mainstream and four major ground water springs.

Effluent conditions predominate in the upland portions of the watershed, except for a local influent reach at the site of a former hydroelectric dam on Altona Flat Rock. Most baseflow is generated in a 6km reach where the river descends from Altona Flat Rock into the Champlain Lowland. The Little Chazy River becomes influent again as it crosses the Champlain Lowland. The point at which the transition occurs varies with baseflow magnitude. At low flow, nearly all of the baseflow is generated in the upper reaches, thus minimizing the impact of ground water runoff from agricultural land. As baseflow increases following runoff events, a greater proportion of baseflow is generated in lowland agricultural regions.

Stream water temperature data are consistent with baseflow observations. Water temperature generally declines through effluent reaches, especially at points of spring inflow, and increases in influent reaches. Water temperature trends, although affected by other variables such as air temperature, residence time and land cover, may be used to independently confirm baseflow generation interpretations from streamflow measurements.

The National Science Foundation, Research Experiences for Undergraduates Program (EAR-0353750) funded this study.