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Hydrologic modelling of the Zackenberg river basin : an applied study using the Soil and Water Assessment Tool

Ahlbäck, Malin LU (2018) In Student thesis series INES NGEK01 20181
Dept of Physical Geography and Ecosystem Science
Abstract
Since the 1980s, the Arctic has experienced an amplified warming of more than twice the rate of the global-mean, leading to large-scale changes in the Arctic hydrologic system, ultimately having cascading feedbacks on the global climate. However, few of today’s distributed models manage to capture the complex processes in Arctic hydrology, and therefore, the aim of this thesis was to evaluate the usage of the distributed Soil and Water Assessment Tool (SWAT) model, to see whether it could capture the different surface water paths and processes characterizing the Arctic water cycle. The model was applied on the Zackenberg river basin, situated in Northeastern Greenland, using spatial data of topography, soil, and vegetation cover, together... (More)
Since the 1980s, the Arctic has experienced an amplified warming of more than twice the rate of the global-mean, leading to large-scale changes in the Arctic hydrologic system, ultimately having cascading feedbacks on the global climate. However, few of today’s distributed models manage to capture the complex processes in Arctic hydrology, and therefore, the aim of this thesis was to evaluate the usage of the distributed Soil and Water Assessment Tool (SWAT) model, to see whether it could capture the different surface water paths and processes characterizing the Arctic water cycle. The model was applied on the Zackenberg river basin, situated in Northeastern Greenland, using spatial data of topography, soil, and vegetation cover, together with observed meteorological data from Zackenberg climate station. The model was evaluated by comparing simulated river discharge in Zackenberg river to observations, using Nash-Sutcliffe Efficiency (NSE) and Coefficient of determination (R2), and by comparing simulated water flows to previously modelled fluxes. The modelled river discharge had a NSE and R2 of 0.62, indicating good agreement. Glacier melt was estimated to a mean of 930 mm w.e./year, within the range of previous estimates, while snowmelt was largely underestimated with a value of 96 mm w.e/year, possibly caused by topographic influences on snow distribution and precipitation data input. The model successfully captured seasonal freezing- and thawing cycles, but largely simplified active layer dynamics. The results indicate that the null hypothesis may be rejected. For future improvements, the methodology should include the usage of elevation bands and coupling to heat transfer algorithms, to fully capture snow distribution and seasonal permafrost dynamics. (Less)
Popular Abstract
The Arctic, defined as the area North of the Polar Circle, has in recent years experienced a warming twice the rate compared to the global mean. The Arctic water cycle is sensitive to even minor changes in temperature due to the fine balance between the frozen and liquid state of water, and can lead to cascading impacts on the global climate and sea-level. However, although its key role on both a regional and global scale, Arctic hydrology has historically been understudied compared to lower and mid–latitudes, both in terms of hydrologic models developed for Arctic regions, as well as available data. In order to better monitor the Arctic ecosystem, research projects have been set up around the northern latitudes, of which the largest... (More)
The Arctic, defined as the area North of the Polar Circle, has in recent years experienced a warming twice the rate compared to the global mean. The Arctic water cycle is sensitive to even minor changes in temperature due to the fine balance between the frozen and liquid state of water, and can lead to cascading impacts on the global climate and sea-level. However, although its key role on both a regional and global scale, Arctic hydrology has historically been understudied compared to lower and mid–latitudes, both in terms of hydrologic models developed for Arctic regions, as well as available data. In order to better monitor the Arctic ecosystem, research projects have been set up around the northern latitudes, of which the largest project is situated in the study area of Zackenberg, in the high Arctic Northeastern Greenland.
The aim of this thesis was to evaluate the Soil and Water Assessment Tool (SWAT) model, to see how well it managed to simulate the different processes and flows within the surface water system in the drainage area to Zackenberg river. The model was set-up using spatial data of topography, soil properties, land use properties, and weather data from the Zackenberg climate station. The model was evaluated by comparing the modelled river flow in Zackenberg river to observations from the same point, using statistical tests such as Nash-Sutcliffe Efficiency (NSE) and Coefficient of determination (R2), as well as by comparing the results to previously modelled flows.
The modelled river discharge got a NSE and R2 of 0.62, indicating good agreement. Glacier melt was estimated to a mean of 930 mm w.e./year, therefore within the range of previous estimates, while snowmelt was largely underestimated with a value of 96 mm w.e/year, possibly caused by the many mountains in the study area, which influenced snow depths and precipitation differences with height. The model successfully captured the timing of freezing and melting of the frozen ground, but it oversimplified the gradual melting of the uppermost layer during summer. For future improvements, the methodology should therefore include the usage of elevation bands, which better can model the differences in snow depth and precipitation along a mountain slope, and coupling to heat transfer algorithms, to better model the melting of the frozen ground during summer. (Less)
Please use this url to cite or link to this publication:
author
Ahlbäck, Malin LU
supervisor
organization
course
NGEK01 20181
year
type
M2 - Bachelor Degree
subject
keywords
Greenland, SWAT, High Arctic, Distributed Hydrologic Modelling, GIS, surface Water
publication/series
Student thesis series INES
report number
453
language
English
additional info
External supervisor: Magnus Lund, Aarhus University, Department of Bioscience
id
8947872
date added to LUP
2018-06-11 13:41:01
date last changed
2018-06-11 13:41:01
@misc{8947872,
  abstract     = {Since the 1980s, the Arctic has experienced an amplified warming of more than twice the rate of the global-mean, leading to large-scale changes in the Arctic hydrologic system, ultimately having cascading feedbacks on the global climate. However, few of today’s distributed models manage to capture the complex processes in Arctic hydrology, and therefore, the aim of this thesis was to evaluate the usage of the distributed Soil and Water Assessment Tool (SWAT) model, to see whether it could capture the different surface water paths and processes characterizing the Arctic water cycle. The model was applied on the Zackenberg river basin, situated in Northeastern Greenland, using spatial data of topography, soil, and vegetation cover, together with observed meteorological data from Zackenberg climate station. The model was evaluated by comparing simulated river discharge in Zackenberg river to observations, using Nash-Sutcliffe Efficiency (NSE) and Coefficient of determination (R2), and by comparing simulated water flows to previously modelled fluxes. The modelled river discharge had a NSE and R2 of 0.62, indicating good agreement. Glacier melt was estimated to a mean of 930 mm w.e./year, within the range of previous estimates, while snowmelt was largely underestimated with a value of 96 mm w.e/year, possibly caused by topographic influences on snow distribution and precipitation data input. The model successfully captured seasonal freezing- and thawing cycles, but largely simplified active layer dynamics. The results indicate that the null hypothesis may be rejected. For future improvements, the methodology should include the usage of elevation bands and coupling to heat transfer algorithms, to fully capture snow distribution and seasonal permafrost dynamics.},
  author       = {Ahlbäck, Malin},
  keyword      = {Greenland,SWAT,High Arctic,Distributed Hydrologic Modelling,GIS,surface Water},
  language     = {eng},
  note         = {Student Paper},
  series       = {Student thesis series INES},
  title        = {Hydrologic modelling of the Zackenberg river basin : an applied study using the Soil and Water Assessment Tool},
  year         = {2018},
}