Research on Design and Operation Method of Dewater and Filled System for Cushion Pool of High Dams ——Taking the project of BHT hydropower plant in China as an example

Dam is set in large hydropower station. Cushion pool is built behind the dam for the flood discharge and energy dissipation of the reservoir. Operation of flood discharge and energy dissipation for some time, Cushion pool is dewatering and structure safety of which is study, then cushion pool is filled. Temporary dewater and filled system is used by previous engineer, but is arranged and controlled hard. Based on need of the cushion pool dewatering and filling, for an example of Baihetan hydropower station, necessity and feasibility are study. Then a permanent dewatering and filling system is designed for cushion pool. Design principle and arrange method are described. Many technical difficulties are study and resolved such as effect of valley deformation on the control system of dewatering and filling, demand of dewatering and filling device parameter, performance quota formulate based on large water level amplitude, protective measures in the working condition of much silt on the downstream and humidity in the equipment room of the second-dam and project of dewater drainage outlet under the water. By gravity drainage and filling based on water level difference and pump drainage, much electric energy is saved and personnel operating environment and working conditions are improved.

The scale and effect of public investments in flood control infrastructure in Serbia from 2009 to 2021

Flood control structures play an important role in saving lives and property during floods, especially due to climate change issues. The construction, reconstruction, and rehabilitation of hydraulic structures are compliant with their maintenance and are performed periodically and preventively in order to achieve their required functional safety. However, over the years, investments in flood protection, i.e. the reduction of possible damage caused by the harmful effects of water, mostly implied investments in embankments. Investments in high dams are insufficient in terms of their importance, structure complexity, and failure risk.

Flood hazard in Slovenia and assessment of extreme design floods

Due to the lack of hydrological measurements in the torrential areas and smaller catchment areas of Slovenian rivers, in accordance with the European Floods Directive, we used an empirical equation to estimate the magnitude of a 500-year flood (Q500). In this paper, we critically evaluate the proposed empirical equations for estimating the Q500 discharge, as defined in the Slovenian Rules on the methodology for determining areas at risk of floods and related erosion of inland waters and the sea, and on the method of classifying land into risk classes. In this assessment, we use publicly available measured data from Slovenia’s hydrological monitoring network and data on extreme flows for selected Slovenian high dams, and thus compare the database with empirical equations for determining extreme flows in Europe and elsewhere in the world that are used for planning high dams. Although the reach of the Q500 flood line determines the area of residual flood danger, it makes sense to abandon the determination of extreme flows in Slovenia using empirical equations and move to a hydrological-hydraulic modelling system using modern software tools.

Flood Routing Process and High Dam Interception of Natural Discharge from the 2018 Baige Landslide-Dammed Lake

The outburst flood of the Baige landslide dam caused tremendous damage to infrastructure, unfinished hydraulic buildings, roads, and bridges that were built or under construction along the Jinsha River. Can downstream hydraulic buildings, such as high dams with flood control and discharge function, accommodate outburst floods or generate more serious losses due to wave overtopping? In this study, the unsteady flow of a one-dimensional hydraulic calculation was used to simulate natural flood discharge. Assuming a high dam (Yebatan arch dam) is constructed downstream, the flood processes were carried out in two forms of high dam interception (complete interception, comprehensive flood control of blocking and draining). Moreover, three-dimensional visualization of the inundation area was performed. Simulation results indicate that the Yebatan Hydropower Station can completely eliminate the outburst flood risk even under the most dangerous situations. This station can reduce the flood peak and delay the peak flood arrival time. Specifically, the flood peak decreased more obviously when it was closer to the upstream area, and the flood peak arrival time was more delayed when the flood spread further downstream. In addition, the downstream water depth was reduced by approximately 10 m, and the inundation area was reduced to half of the natural discharge. This phenomenon shows that hydraulic buildings such as high dams can reduce the inundation area of downstream farmlands and extend the evacuation time for downstream residents during the flood process, thus reducing the loss of life and property.

A Brief Theoretical Analysis on the Ventilation Characteristics of the Multi-Intake-Well Air Supply System in a Spillway Tunnel

It is of great significance to study the ventilation characteristics of air supply systems in spillway tunnels, especially for high dams. In this paper, a brief theoretical approach to evaluate the ventilation characteristics of a multi-intake-well air supply system was established, which was mainly derived from the Bernoulli equation and continuity equation. With this approach, an analysis of the ventilation characteristics of the Jinping-I project spillway tunnel was carried out. A comparison of the theoretical results and prototype data suggested the theoretical approach to be valid and practical. The value of the drag coefficient at the air-water interface should be calibrated before evaluation because the drag coefficient is crucial for the accuracy of theoretical results. In addition, the influences of certain structural factors of the spillway tunnel and air intake well on the ventilation characteristics of multi-intake-well air supply systems are investigated.

Experimental Study on the Effects of Vegetation on the Dissipation of Supersaturated Total Dissolved Gas in Flowing Water

High dam discharge can lead to total dissolved gas (TDG) supersaturation in the downstream river, and fish in the TDG-supersaturated flow can suffer from bubble disease and even die. Consequently, it is of great value to study the transport and dissipation characteristics of supersaturated dissolved gas for the protection of river fish. Floodplains may form downstream of high dams due to flood discharge, and the plants on these floodplains can affect both the hydraulic characteristics and TDG transport of the flowing water. In this study, the velocity distribution and the retention response time under different flow conditions and vegetation arrangements were studied in a series of experiments. The retention time was significantly extended by the presence of vegetation, and an empirical formula for calculating the retention time was proposed. In addition, the responses of the dissipation process of supersaturated TDG to hydraulic factors, retention time, and vegetation area coefficient were analyzed. The dissipation of supersaturated TDG significantly increased with increases in the vegetation area coefficient in the water. To quantitatively describe the TDG dissipation process in TDG-supersaturated flow under the effect of vegetation, the TDG dissipation coefficient was fitted and analyzed. The basic form of the formula for the dissipation coefficient involving various influence factors was determined by dimensional analysis. An equation for calculating the TDG dissipation coefficient of flowing water with vegetation was proposed by multivariate nonlinear fitting and was proven to have great prediction accuracy. The calculated method developed in this paper can be used to predict TDG dissipation in flowing water with vegetation and is of great significance for enriching TDG prediction systems.

Investigation on hydrothermal processes in a large channel-type reservoir using an integrated physics-based model

Hydrothermal processes are vital for the aquatic ecology and environments of a river. In recent decades, as high dams have been increasingly built in large rivers, many channel-type reservoirs have formed. With a considerable amount of water being impounded, the original riverine hydrothermal regimes are modified or even profoundly changed. Existing studies are mainly focused on the thermal stratification in lake-type reservoirs with weak vertical mixing, while channel-type reservoirs are rarely investigated where the vertical mixing is relatively strong due to the large riverine discharge. In this study, the impact of dam operation on the Three Gorges Reservoir (TGR) was investigated, including the water level, discharge and temperature, by applying an integrated physics-based model developed using field data. The present numerical model was built based on a hydrothermal dynamic model and a box model. The results indicate that the reservoir has caused a significant thermal lag between the inflow and outflow, with the temperature difference being up to 5 °C. A highly correlated dependency has been found between the dam-regulated water level and the inflow/outflow temperature difference. The present method and conclusions are potentially useful for managing the TGR and other channel-type reservoirs.

Rational placement of measuring systems in high dams

To solve the problem of rational placement of measuring systems in concrete dams, the experience of full-scale observations of horizontal displacements and stresses in the body of the arch dam of Inguri HPP (Georgia) was used with the use of statistical processing of the results of observations and the Barlow-Hunter-Proshan mathematical model. The type of the law of distribution of horizontal displacements and arch stresses was established by analyzing the histograms of these measured indicators of the static state of the structure. It is established that the change of horizontal displacements along the dam height is well described by the one-sided normal distribution law, and the arch stresses in the controlled alignment - by the normal distribution law. The laws of distribution of random variables are established. Using the Barlow-Hunter-Proshan mathematical model enabled the use of economic criteria on the basis of the frequency characteristics of the indicators of trouble-free operation of the construction and obtain the recurrence relation for the sequence of coordinate points of the measuring systems. The results of calculations of the coordinates of the recommended location of straight plumb lines in the center console and tensometric rosettes in the measuring range of the Ingur dam at the level of 210 m for a rational placement scheme are presented. The calculation showed that the number of measuring systems installed in the body of the Ingur dam exceeds the optimum value.