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North Carolina State University (2016)

Long-Term Terrestrial Hydrologic Cycle Changes and the Role of Watershed Scale Spatial Influences

Rice, Joshua Sayre

Titre : Long-Term Terrestrial Hydrologic Cycle Changes and the Role of Watershed Scale Spatial Influences.

Auteur : Rice, Joshua Sayre

Université de soutenance : North Carolina State University

Grade : Doctor of Philosophy (PhD) 2016

Résumé
The movement of water is a primary agent for the transport of mass and energy around the Earth, and is critically important to many of the Earth’s systems. Hydrologic fluxes influence the function of the climate system, provide critical support for living organisms, and provide couplings between the water, energy, and biogeochemical cycles. Fluxes of moisture within the terrestrial portion of the larger hydrologic cycle are particularly important from a societal perspective as streamflow is one of the primary sources of renewable freshwater on the Earth. The cultivation of knowledge concerning how changes in streamflow occur is then an area of research that is of broad scientific and societal relevance. The research presented here considers changes in streamflow across much of the conterminous United States between 1940 and 2009 and delves into the relationship between the magnitude of observed changes and spatial characteristics of the watersheds in which those changes occurred. Chapter one of this dissertation examines temporal changes in streamflow from a time domain perspective. Chapter two of this work also considers temporal changes in streamflow, but from a frequency domain perspective. Chapter three of this research examines changes in the partitioning of precipitation into streamflow. The fourth chapter of this dissertation synthesizes a finding common to each of the preceding three chapters. The results of these chapters document widespread changes in the terrestrial hydrologic cycle, and streamflow specifically, across the conterminous United States between 1940 and 2009. The magnitude of these changes were found to be clearly related to the internal spatial characteristics of the watersheds in which they occur. Interaction effects between various spatial characteristics were also found to be strongly related to the magnitude of observed changes. A pattern that emerged from chapters one through three of this project is of increased trend magnitudes in non-reference watershed, relative to reference watersheds. These results all indicate that the spatial characteristics of the landscape, both natural and anthropogenic, play a strong role in determining how watershed scale hydrologic changes occur over time.

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Page publiée le 23 octobre 2016, mise à jour le 9 octobre 2018