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INFLUENCES OF CLIMATE CHANGE AND VARIABILITY ON BASEFLOWS

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Date Issued:
2019
Abstract/Description:
Baseflow is the portion of the streamflow that is sustained between precipitation events, fed to streams by delayed pathways. Baseflow estimation and evaluation are two critical and essential tasks for water quality and quantity, drought management, water supply, and groundwater protection. In this research study, the influences of climate change and variability on baseflow derived from hundreds of watersheds in the continental United States are evaluated. Baseflows are estimated using streamflow data from these watersheds that are least affected by anthropogenic influences. In the initial phase of the study, an exhaustive evaluation of four different baseflow separation methods is carried out using streamflow data at several sites from the South Atlantic-Gulf region which includes a geographical region comprising of nine states in the southeastern U.S. Baseflows are estimated at different temporal scales and are used to assess the performances of different methods over a 44-year period starting from the year 1970 and the best method among these methods is selected for further analysis. Assessments of climate change influence on baseflows are then carried out using two nonparametric statistical trend tests (viz., Spearman’s Rho (SR) and Mann-Kendall (MK)). Trends in baseflows are evaluated at 574 sites located within the watersheds in the U.S. that are known to be least impacted by human influences. Trends were determined for annual maximum, mean, and median baseflows for the period 1970-2013. Spatially non-uniform trends and changes in characteristics of baseflows and strong influences of past precipitation events on the baseflow extremes were noted across the continental U.S. Some regions have shown decreasing baseflow trends and these are cause for concern and have severe implications for drought mitigation plans and low-flow management strategies in several watersheds in the U.S. In the final phase of the study influences of climate variability on baseflow manifested through different phases of individual and coupled oceanic and atmospheric oscillations are evaluated. Baseflows at 574 sites separated by temporal windows that coincide with two or more phases of different decadal, quasi-decadal and multi-year oscillations (viz., Pacific decadal oscillation (PDO), North Atlantic oscillation (NAO), Atlantic multidecadal oscillation (AMO), and El Niño-southern oscillation (ENSO)) are evaluated for statistically significant changes using nonparametric statistical hypothesis tests. Results from the study indicate that unlike climate change influences, climate variability effects are noted only in few specific physiographic regions of the U.S. This study documents an exhaustive and comprehensive assessment of changes in baseflows due to changing climate and results from this work can aid in short- and long-term management of low flows at a regional level that supports sustainable aquatic environment and handle droughts effectively.
Title: INFLUENCES OF CLIMATE CHANGE AND VARIABILITY ON BASEFLOWS.
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Name(s): Chen, Hao , author
Teegavarapu, Ramesh S. V., Thesis advisor
Florida Atlantic University, Degree grantor
Department of Civil, Environmental and Geomatics Engineering
College of Engineering and Computer Science
Type of Resource: text
Genre: Electronic Thesis Or Dissertation
Date Created: 2019
Date Issued: 2019
Publisher: Florida Atlantic University
Place of Publication: Boca Raton, Fla.
Physical Form: application/pdf
Extent: 221 p.
Language(s): English
Abstract/Description: Baseflow is the portion of the streamflow that is sustained between precipitation events, fed to streams by delayed pathways. Baseflow estimation and evaluation are two critical and essential tasks for water quality and quantity, drought management, water supply, and groundwater protection. In this research study, the influences of climate change and variability on baseflow derived from hundreds of watersheds in the continental United States are evaluated. Baseflows are estimated using streamflow data from these watersheds that are least affected by anthropogenic influences. In the initial phase of the study, an exhaustive evaluation of four different baseflow separation methods is carried out using streamflow data at several sites from the South Atlantic-Gulf region which includes a geographical region comprising of nine states in the southeastern U.S. Baseflows are estimated at different temporal scales and are used to assess the performances of different methods over a 44-year period starting from the year 1970 and the best method among these methods is selected for further analysis. Assessments of climate change influence on baseflows are then carried out using two nonparametric statistical trend tests (viz., Spearman’s Rho (SR) and Mann-Kendall (MK)). Trends in baseflows are evaluated at 574 sites located within the watersheds in the U.S. that are known to be least impacted by human influences. Trends were determined for annual maximum, mean, and median baseflows for the period 1970-2013. Spatially non-uniform trends and changes in characteristics of baseflows and strong influences of past precipitation events on the baseflow extremes were noted across the continental U.S. Some regions have shown decreasing baseflow trends and these are cause for concern and have severe implications for drought mitigation plans and low-flow management strategies in several watersheds in the U.S. In the final phase of the study influences of climate variability on baseflow manifested through different phases of individual and coupled oceanic and atmospheric oscillations are evaluated. Baseflows at 574 sites separated by temporal windows that coincide with two or more phases of different decadal, quasi-decadal and multi-year oscillations (viz., Pacific decadal oscillation (PDO), North Atlantic oscillation (NAO), Atlantic multidecadal oscillation (AMO), and El Niño-southern oscillation (ENSO)) are evaluated for statistically significant changes using nonparametric statistical hypothesis tests. Results from the study indicate that unlike climate change influences, climate variability effects are noted only in few specific physiographic regions of the U.S. This study documents an exhaustive and comprehensive assessment of changes in baseflows due to changing climate and results from this work can aid in short- and long-term management of low flows at a regional level that supports sustainable aquatic environment and handle droughts effectively.
Identifier: FA00013366 (IID)
Degree granted: Dissertation (Ph.D.)--Florida Atlantic University, 2019.
Collection: FAU Electronic Theses and Dissertations Collection
Note(s): Includes bibliography.
Subject(s): Climatic changes
Streamflow
Base flow (Hydrology)
Held by: Florida Atlantic University Libraries
Sublocation: Digital Library
Persistent Link to This Record: http://purl.flvc.org/fau/fd/FA00013366
Use and Reproduction: Copyright © is held by the author with permission granted to Florida Atlantic University to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Use and Reproduction: http://rightsstatements.org/vocab/InC/1.0/
Host Institution: FAU
Is Part of Series: Florida Atlantic University Digital Library Collections.