Date of Award

5-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Joshua C. Galster

Committee Member

Kirk R. Barrett

Committee Member

Clement A. Alo

Abstract

The population density of the United States has more than tripled over the last century causing increased urbanization and greater anthropogenic influences in previously rural watersheds. Urbanization leads to increased impervious surfaces and the compaction of soils, both of which combine to reduce infiltration rates. Reduced baseflow can directly limit water availability for approximately half the U.S. population that depends on surficial waters for their drinking water. This project empirically investigated the baseflow-urbanization relationship on a geographic and temporal scale that has not been previously investigated. USGS river gage data in 11 eastern U.S. states (NY south of the Adirondacks, CT, NJ, PA, DE, MD, ME, VA, NC, SC, and GA) were used to examine the effects of urbanization on baseflow. Gage selection was based on the following criteria: continuous record (>25 years), unregulated, and a drainage area < 1,000 km2 (400mi2). Three metrics of annual baseflow were used; 1) baseflow per unit drainage area (BF), 2) ratio of BF to precipitation (BF/P), and 3) and BF as a fraction of total flow (BF/TF). Using population density as a proxy for urbanization, fixed effect models were used to determine the baseflow-population density relationship. Watershed geomorphic characteristics such as topography and associated soil properties were found to have an impact on stream baseflow. Statistical analysis revealed generally positive correlations between baseflow and population in the Appalachian Province while the Coastal Plain showed decreasing baseflow with increased population density. I hypothesize that the Coastal Plain, with its flatter slopes and more permeable soils, suffers greater infiltration losses than gains from urban recharge, resulting in lower baseflow. The Appalachians have the reverse, with an increase in urbanization causing an increase in baseflow. These results will provide water managers with a way to assess the threat that urbanization poses to dry-weather water availability.

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