A modelling approach for evaluating impacts of hydropeaking in a sub-arctic river

Abstract. The release of pulses of water to increase hydroelectric power production at hydropower dams to meet daily peaks in electricity demands is called hydropeaking. Due to energy supply and demand fluctuations, the energy markets direct hydropower companies to balance load fluctuations through variations in power generation which result in flow regulation. More recently, this regulation is being carried out at shorter time intervals i.e., intra-daily and intra-hourly levels. The hydropeaking phenomenon increases drastically at shorter time intervals, severely impacting the riverine and riparian ecosystem. Social, economic, and ecological impacts arise from short-term hydropeaking. Furthermore, recreational services offered by the river are also impacted. This research develops a novel methodology for assessing these impacts in a strongly regulated sub-arctic river in Finland, i.e., Kemijoki River, Ossauskoski-Tervola reach. The methodology combines assessment of seasonal variations in sub-daily hydropeaking, two-dimensional hydrodynamic modelling, and a high-resolution land cover map developed through supervised land use classification via a machine learning algorithm. The results obtained include; the identification of a zone of influence of hydropeaking at sub-daily levels during each season, the total and class-wise area affected during each peaking event, and vulnerability zonation for water-based recreation in the river reach. The overall area of reach affected by peaking in Winter was (1.05 km2), Spring (0.96 km2), Summer (1.39 km2), and Autumn (0.66 km2). A vulnerability mapping was also carried out for the suitability of water-based recreation in the study reach. The novel methodology developed in this research which defines the vulnerable zone of hydropeaking can be used as the first step in detailed impacts assessment studies such as those for impacts on fish habitat and sediment transport processes in the river. The hydropeaking-influenced zone can be used to set thresholds for ecological flows and ramping rates downstream of power stations and opens avenues for future research, development, and policy endeavors for riparian ecosystem impact assessment and mitigation

Random block stability and anchoring design for underground caverns in a hydro-power station

Random blocks in underground tunnels and in grand power caverns are the unstable blocks cut by random joints or fractures in the bedrock. Designers often reinforce these blocks by using systematic anchors however their length and space are difficult to determine because of the randomness of blocks position and the indeterminacy of the blocks geometric characters. By the study of geological conditions and the rock structure of the underground caverns in the hydropower station, the regularities of distribution of the possible random joints were concluded. This enabled the random blocks to be orientated by combining joints with other joints, or combining joints with I and II definite structural planes. The geometric characteristics and stabilities of the random blocks were determined by using stability calculations according to block theory. From this the optimal anchor length could be defined, which could be referred to as a theoretical base for the length of the systematic anchors.published_or_final_versionThe 10th IAEG International Congress: Engineering Geology for Tomorrow's Cities, Nottingham, United Kingdom, 6-10 September 2006. In Proceedings of the 10th IAEG International Congress, 2006, p. 547-55

Sediment transport in Säveån and its implications for erosion and bank stability

This master thesis study is a preliminary investigation of the Säveån River as part of the Swedish Geotechnical Institute’s (SGI) landslide risk assessment project. The main objectives include building a hydrodynamic model for the river, estimating sediment transport along the river, assessing the implications for erosion and bank stability and evaluating climate change effects on sediment transport. The study section is from downstream Jonsered hydropower plant to the outlet at Göta Älv. The model selected for the hydrodynamic study is the one dimensional river analysis model HEC-RAS. ArcGIS was used in combination with Hec-GeoRAS to map out the river and extract cross sections from a Digital Elevation Model (DEM) of the river. Steady flow and sediment transport simulations were then done to obtain the hydrodynamics and sediment transport of the river respectively. Model results revealed schematized cross section 12500 close to the upstream end of the study reach to have the most erosion. This section was then used as an example to find the loss in slope stability due to sediment transport using the model SLOPE/W. Climate change simulations were then done with flow data from a simulated period of 2021-2050 and 2069-2098 and compared to a reference period of 1963-1992. Results show that sediment transport is to increase more than twice moving from the reference period to the period 2021-2050 and increase again more than twice from this period to the period 2069-2098 which signifies the end of the century

Monitoring of Landslides in Mountainous Regions based on FEM Modelling and Rain Gauge Measurements

Vietnam is a country heavily influenced by climate change. The effect of climate change leads to a series of dangerous phenomena, such as landslides. Landslides occur not only in the mountainous province, but also in Delta provinces, where hundreds of landslides are reported annually in the North-Western provinces of Vietnam. These events have catastrophic impact to the community as well as the economy. In mountainous areas, the conditions for landslides to occur are met frequently, especially after heavy rains or geological activity, causing harm to the community as well as damaging or destroying much needed infrastructure and key transport routes. However, in Vietnam, investment in mountainous regions has been often lower than in urban areas. The meteorology monitoring and forecasting systems are ill equipped and overloaded, so they cannot deliver earlier and more accurate forecasts for complex weather events, unable to provide timely warnings. It can be seen that in countries that landslide often occur, researchers have been trying to develop low cost and efficient landslide detection system. This paper precisely addressed the problems mentioned, by designing and implementing an efficient and reliable Landslide Monitoring and Early Warning (LMnE) system based on the 3G/2G mobile communication system, and a rain gauge at the field site along with a carefully FEM (finite element method) simulation using the rain density information on the server. The system uses advanced processing algorithms combining obtained data at the central station

Study on Analog Theory of Rock Mass Simulation and Its Engineering Application

During construction of 3D geological models, it is difficult to determine the uniform between geological model and true model. As a comprehensive index, rock quality designation (RQD) is reliable to assess the rationality of geological models. Unfortunately, The RQD of rockmass is determined completely by the deterministic threshold value and directions of the scan lines presently. To avoid this drawback, the modified method of the RQD value based on the threshold value and 3D space is proposed in this paper. Simultaneously, the analogue-simulation method based on rupture mechanism and classification of discontinuities is proposed. The elliptical discontinuity is considered for general discontinuity, and the special discontinuities, such as bedding, fault, and interlayer are dealt with individually. The accuracy of the 3D model is verified by the modified RQD. The 3D model of the rockmass is analogue simulated through repetitively obtaining data from the interval confidence of geometrical parameters of discontinuities, which are determined by a mass of data derived from field investigation. Besides, the dam base of the Xiangjiaba hydropower station is taken as an example, and the 3D model of the dam base is analog-simulated; its stability is evaluated by DDA method. The safety coefficient of the dam base is obtained by utilizing the overload method

CFD analyses and performance comparison of micro-hydropowder plants

The project concerns the hydropower renewable energy technology at its micro scale: thanks to an internship performed with the Belgian startup TurbulentHydro, the purpose of this Master Thesis is to evaluate the energy performance of 2 di erent models currently under investigation: the so-called Flatblades and Streamlines con gurations. These layouts are similar in shape but di erent both in dimension and for the turbine used. After a little introduction on renewable energies and hydropower technology, the selected CFD simulation procedure and all its options have been explained as well as the choice of the turbulence model to apply, computing the meaningful parameters to add in the model. This dissertation highlights the uid dynamics behaviour by means of suitable softwares for this purpose: Autodesk Inventor, the 3D CAD mechanical design software in order to build, and edit when necessary, the geometries of the models considered, MeshMixer, a state-of-art software for locally adjusting the mesh of the starting model and OpenFOAM, a free and open source CFD program in order to run and evaluate any details of the analysis, simulating the operation conditions by means of its components and tools. Eventually, the most important CFD results are presented. Di erent con gurations bring di erent results. Regarding Flatblades model, the scope was re ned the CFD initial setup in order to achieve results as close to the real case validation as possible whereas, for Streamlines model, an additional new component has been added for improving the current design in terms of energy output at the turbine level. At the end, conclusions stated possible re nements and improvements for these simulations as well as uncertainties arose from the results that might be avoided for the next stages

Modeling water resources management at the basin level: review and future directions

Water quality / Water resources development / Agricultural production / River basin development / Mathematical models / Simulation models / Water allocation / Policy / Economic aspects / Hydrology / Reservoir operation / Groundwater management / Drainage / Conjunctive use / Surface water / GIS / Decision support systems / Optimization methods / Water supply