Date of Award

2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil Engineering

Committee Chair

James Cruise

Committee Member

Richard McNider

Committee Member

Robert Griffin

Committee Member

Robert Peters

Committee Member

Kathleen Leonard

Committee Member

Micheal Anderson

Subject(s)

Evapotranspiration--Southern states., Hydrology--Southern states., Soil moisture conservation--Southern states., Southern states--Climate.

Abstract

As a major term in both the energy and water budgets, evapotranspiration (ET) has the potential to exert significant impacts on both climate and hydrology, from the basin, regional and global scales. This dissertation will examine of the impacts of ET on climatology and hydrology in the Southeastern (SE) region of the United States. It is presented in two complementary narratives throughout this document; an analysis of climatological impacts of ET due to land use change and a hydrological analysis, examining the spatial and temporal roles of ET with respect to streamflow. The climatological analysis investigates a regional climate anomaly from an observational perspective but within the conceptual framework of variations in the energy budget. Long-term temperature and land cover datasets are employed to examine the linking trends. Eddy flux tower data is compiled over the region along with satellite data and a crop model to quantify the different biogeophysical characteristics associated with the major LULC changes. The hydrological component of this dissertation investigates the spatial and temporal impacts of ET on streamflow with an overall goal to evaluate the impact of ET in an effort to determine the spatial and temporal scales needed to model streamflow. Streamflow time series data are constructed from 57 gauges that represent the SE, both in terms of spatial coverage and geomorphology. Several ET models are reviewed, compared and analyzed representing the most common methods and differing spatial scales. Traditional and informational statistics are employed to uncover the temporal and spatial extent of where ET’s influence on streamflow becomes significant. It was found that indeed ET does have a significant impact on the climate in the Southeastern U.S. and contributes to an anomalous cooling trend in the overall climate of the SE. The energy budget showed a decrease of a 2.5 $w m^{-2}$ due to the latent energy effects of land cover change from agricultural to forest. Additionally, there is a strong annual cycle in the ET data in the Southeast but it does not impart as strong of a cycle to the streamflow; however, there is considerable shared information between the ET and streamflow. There were little spatial effects evident in the watershed analysis.

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