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Hydrograph variances over different timescales in hydropower production networks
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.ORCID iD: 0000-0003-4036-424X
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.
2016 (English)In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 52, no 8, p. 5829-5846Article in journal (Refereed) Published
Abstract [en]

The operation of water reservoirs involves a spectrum of timescales based on the distribution of stream flow travel times between reservoirs, as well as the technical, environmental, and social constraints imposed on the operation. In this research, a hydrodynamically based description of the flow between hydropower stations was implemented to study the relative importance of wave diffusion on the spectrum of hydrograph variance in a regulated watershed. Using spectral decomposition of the effluence hydrograph of a watershed, an exact expression of the variance in the outflow response was derived, as a function of the trends of hydraulic and geomorphologic dispersion and management of production and reservoirs. We show that the power spectra of involved time-series follow nearly fractal patterns, which facilitates examination of the relative importance of wave diffusion and possible changes in production demand on the outflow spectrum. The exact spectral solution can also identify statistical bounds of future demand patterns due to limitations in storage capacity. The impact of the hydraulic description of the stream flow on the reservoir discharge was examined for a given power demand in River Dalälven, Sweden, as function of a stream flow Peclet number. The regulation of hydropower production on the River Dalälven generally increased the short-term variance in the effluence hydrograph, whereas wave diffusion decreased the short-term variance over periods of <1 week, depending on the Peclet number (Pe) of the stream reach. This implies that flow variance becomes more erratic (closer to white noise) as a result of current production objectives.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2016. Vol. 52, no 8, p. 5829-5846
National Category
Water Engineering
Identifiers
URN: urn:nbn:se:kth:diva-201607DOI: 10.1002/2015WR017775ISI: 000383684400007Scopus ID: 2-s2.0-84987994865OAI: oai:DiVA.org:kth-201607DiVA, id: diva2:1073327
Note

QC 20170214

Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2017-05-30Bibliographically approved
In thesis
1. Effects of Watershed Dynamics on Water Reservoir Operation Planning: Considering the Dynamic Effects of Streamflow in Hydropower Operation
Open this publication in new window or tab >>Effects of Watershed Dynamics on Water Reservoir Operation Planning: Considering the Dynamic Effects of Streamflow in Hydropower Operation
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Water reservoirs are used to regulate river discharge for a variety of reasons, such as flood mitigation, water availability for irrigation, municipal consumption and power production purposes. Recent efforts to increase the amount of renewable power production have seen an increase in intermittent climate-variable power production due to wind and solar power production. The additional variable energy production has increased the need for regulating the capacity of the electrical system, to which hydropower production is a significant contributor. The hydraulic impact on the time lags of flows between production stations have often largely been ignored in optimization planning models in favor of computational efficiency and simplicity. In this thesis, the hydrodynamics in the stream network connecting managed reservoirs were described using the kinematic-diffusive wave (KD) equation, which was implemented in optimization schemes to illustrate the effects of wave diffusion in flow stretches on the resulting production schedule. The effect of wave diffusion within a watershed on the variance of the discharge hydrograph within a river network was also analyzed using a spectral approach, illustrating that wave diffusion increases the variance of the hydrograph while the regulation of reservoirs generally increases the variance of the hydrograph over primarily short periods. Although stream hydrodynamics can increase the potential regulation capacity, the total capacity for power regulation in the Swedish reservoir system also depends significantly on the variability in climatic variables. Alternative formulations of the environmental objectives, which are often imposed as hard constraints on discharge, were further examined. The trade-off between the objectives of hydropower production and improvement of water quality in downstream areas was examined to potentially improve the ecological and aquatic environments and the regulation capacity of the network of reservoirs.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. p. 70
Series
TRITA-HYD ; 2017:01
Keywords
reservoir operation, dispersion processes, wave diffusion, multi-objective operation, water resource management, discharge variability, power spectrum analysis
National Category
Water Engineering
Research subject
Civil and Architectural Engineering
Identifiers
urn:nbn:se:kth:diva-201612 (URN)978-91-7729-278-4 (ISBN)
Public defence
2017-03-03, F3, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Supervisors
Note

QC 20170210

Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2017-02-10Bibliographically approved

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