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Effects of Watershed Dynamics on Water Reservoir Operation Planning: Considering the Dynamic Effects of Streamflow in Hydropower Operation
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Hydraulic Engineering.ORCID iD: 0000-0003-4036-424X
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
Keyword [en]
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: urn:nbn:se:kth:diva-201612ISBN: 978-91-7729-278-4 (print)OAI: oai:DiVA.org:kth-201612DiVA, id: diva2:1073430
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
List of papers
1. Incorporating Hydrologic Routing into Reservoir Operation Models: Implications for Hydropower Production Planning
Open this publication in new window or tab >>Incorporating Hydrologic Routing into Reservoir Operation Models: Implications for Hydropower Production Planning
2016 (English)In: Water resources management, ISSN 0920-4741, E-ISSN 1573-1650, Vol. 30, no 2, p. 623-640Article in journal (Refereed) Published
Abstract [en]

Increased reliance on variable and intermittent energy sources is likely to lead to a change in the production strategies of hydropower, thereby increasing the importance of accurate forecasting of production. For optimization models applied to water reservoirs, the computational cost increases with the number of reservoirs and future time-steps considered, often requiring simplification of the physical description of the flow dynamics. Here it is demonstrated that deficiency of the model of the flow dynamics on stream-reaches gives rise to errors in short-term planning, which leads to sub-optimal production. Here a simplified hydraulic model based on the kinematic-diffusion wave model was incorporated in the optimization of reservoir production planning. The time-lag distributions of the streams were evaluated for River Dalälven and implemented in a computationally efficient form of the kinematic-diffusion wave equation incorporated in a production optimization algorithm for a series of reservoirs. Compared to using a single time-lag for the water transfer on flow reaches between hydropower stations, the wave diffusion was found to affect the management as a deviation between the actual production and the planned production. The deviation was found to increase with increasing short-term regulation and decreasing Peclet number below about 10. For a sufficiently high Peclet number and long wavelength characterizing individual stream reaches, the distribution of time-lags become sufficiently narrow to motivate being replaced by a simpler description such as the constant time-lag.

Place, publisher, year, edition, pages
Springer Science+Business Media B.V., 2016
National Category
Energy Systems
Identifiers
urn:nbn:se:kth:diva-201603 (URN)10.1007/s11269-015-1181-x (DOI)
Note

QC 20170214

Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2017-11-29Bibliographically approved
2. Hydrograph variances over different timescales in hydropower production networks
Open this publication in new window or tab >>Hydrograph variances over different timescales in hydropower production networks
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
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-201607 (URN)10.1002/2015WR017775 (DOI)000383684400007 ()2-s2.0-84987994865 (Scopus ID)
Note

QC 20170214

Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2017-05-30Bibliographically approved
3. Trade-Offs between phosphorous discharge and hydropower production using reservoir regulation
Open this publication in new window or tab >>Trade-Offs between phosphorous discharge and hydropower production using reservoir regulation
2017 (English)In: Journal of water resources planning and management, ISSN 0733-9496, E-ISSN 1943-5452, Vol. 143, no 9, article id 04017052Article in journal (Refereed) Published
Abstract [en]

The management of water flow using reservoirs for the purpose of hydropower production can have significant impacts on solute transport. Reducing the phosphorous load to downstream areas can be of great importance for aquatic habitats associated with recipient waters, as well as for the overall health of coastal and estuary areas. This study demonstrates a combined operation of a network of reservoirs with the objectives of hydropower production and improvement of water quality in downstream areas using a multiobjective approach and incorporating the transport of phosphorous in the watershed. A genetic optimization method was used to determine the trade-off between power production and mitigation of phosphorous discharge in the reservoir network of the Dalälven River, Sweden. The phosphorous export can be reduced (-5%) with a limited loss of power production (-4.3%), but further reduction is associated with a significant loss in total power production. The trade-off between the two objectives is determined using Pareto diagrams and examined for varying particulate conditions.

Place, publisher, year, edition, pages
American Society of Civil Engineers (ASCE), 2017
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-201608 (URN)10.1061/(ASCE)WR.1943-5452.0000809 (DOI)000408564100005 ()2-s2.0-85021354663 (Scopus ID)
Note

QC 20170214

Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2017-09-27Bibliographically approved
4. Spectral Decomposition of Regulatory Thresholds for Climate–Driven Fluctuations in Hydro- and Wind Power Availability
Open this publication in new window or tab >>Spectral Decomposition of Regulatory Thresholds for Climate–Driven Fluctuations in Hydro- and Wind Power Availability
(English)Article in journal (Other academic) Submitted
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-201610 (URN)
Note

QCR 20170221

Available from: 2017-02-10 Created: 2017-02-10 Last updated: 2017-02-21Bibliographically approved
5. Coupled geomorphologic dispersion and reservoir management
Open this publication in new window or tab >>Coupled geomorphologic dispersion and reservoir management
(English)Manuscript (preprint) (Other academic)
National Category
Water Engineering
Identifiers
urn:nbn:se:kth:diva-201611 (URN)
Note

QC 20170210

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

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