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Change in streamflow response in unregulated catchments in Sweden over the last century
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.ORCID iD: 0000-0002-9202-3159
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.ORCID iD: 0000-0003-2716-4446
2016 (English)In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973Article in journal (Refereed) Published
Abstract [en]

A Fourier spectral analysis of 55-110 years of daily discharge time series in 79 unregulated catchments in Sweden reveals that the discharge power spectrum slope in most of the studied catchments has gradually steepened over time. This statistically significant drift in the periodicity of dominant hydrologic response processes can be attributed to a change in either climatic forcing factors or anthropogenic effects on the land surface, e.g., land-use changes. For those locations for which historical meteorological observations are available (the 41 southernmost catchments), the results of our analyses of changes in precipitation power spectra indicate that local land-use changes within the catchments may affect discharge power spectra more significantly than precipitation pattern changes (resulting from climate change).

By using 1D distributed hydraulic routing, we quantitatively analyze how travel time distributions within stream networks can vary because of anthropogenic impacts, such as changes in stream network spatial coordinates (these stream networks are derived from three maps: two from the present and one from the 1880s), river width modifications, stream channel excavation, and the elimination of thresholds in stream bottom topography that cause exceedingly low local bottom slopes.

The findings that the discharge power spectrum may change significantly over time, implies that conventional, statistically-based parameterization of hydrological models that rely on assumptions of stationarity may be less suited than more physically based parameterization alternatives. This essential information must be considered when performing tasks that involve (peak) flow predictions, such as those for dimensioning and flood risk management purposes.

 

Place, publisher, year, edition, pages
Blackwell Publishing, 2016.
National Category
Oceanography, Hydrology, Water Resources
Identifiers
URN: urn:nbn:se:kth:diva-172935DOI: 10.1002/2015WR018116Scopus ID: 2-s2.0-84980327282OAI: oai:DiVA.org:kth-172935DiVA: diva2:850800
Funder
StandUp
Note

QC 20160823

Available from: 2015-09-02 Created: 2015-09-02 Last updated: 2017-12-04Bibliographically approved
In thesis
1. Peakflow response of stream networks: implications of physical descriptions of streams and temporal change
Open this publication in new window or tab >>Peakflow response of stream networks: implications of physical descriptions of streams and temporal change
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Through distributed stream network routing, it has quantitatively been shown that the relationship between flow travel time and discharge varies strongly nonlinearly with stream stage and with catchment-specific properties.

Physically derived distributions of water travel times through a stream network were successfully used to parameterise the streamflow response function of a compartmental hydrological model. Predictions were found to improve compared to conventional statistically based parameterisation schemes, for most of the modelled scenarios, particularly for peakflow conditions.

A Fourier spectral analysis of 55-110 years of daily discharge time series from 79 unregulated catchments in Sweden revealed that the discharge power spectral slope has gradually increased over time, with significant increases for 58 catchments. The results indicated that the catchment scaling function power spectrum had steepened in most of the catchments for which historical precipitation series were available. These results suggest that (local) land-use changes within the catchments may affect the discharge power spectra more significantly than changes in precipitation (climate change).

A case study from an agriculturally intense catchment using historical (from the 1880s) and modern stream network maps revealed that the average stream network flow distance as well as average water levels were substantially diminished over the past century, while average bottom slopes increased. The study verifies the hypothesis that anthropogenic changes (determined through scenario modelling using a 1D distributed routing model) of stream network properties can have a substantial influence on the travel times through the stream networks and thus on the discharge hydrographs.

The findings stress the need for a more hydrodynamically based approach to adequately describe the variation of streamflow response, especially for predictions of higher discharges. An increased physical basis of response functions can be beneficial in improving discharge predictions during conditions in which conventional parameterisation based on historical flow patterns may not be possible - for example, for extreme peak flows and during periods of nonstationary conditions, such as during periods of climate and/or land use change.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. x, 74 p.
Series
TRITA-HYD, 2015:2
Keyword
Streamflow routing, peakflow predictions, parameterization, hydrological response, stage-dependency, flooded cross-sections, stream networks, backwater effects, temporal change, land use change
National Category
Oceanography, Hydrology, Water Resources
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-172939 (URN)978-91-7595-672-5 (ISBN)
Public defence
2015-09-29, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150903

Available from: 2015-09-03 Created: 2015-09-02 Last updated: 2015-09-28Bibliographically approved

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Åkesson, AnnaRiml, Joakim

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