Reservoir Flood Routing Research Articles

Penentuan Initial Elevation untuk Mendukung Operasi Early Release Bendungan Sadawarna

Modifications of Sadawarna Dam include the addition of a sluice gate that is placed on the right side of the spillway which functions as an early release facility along with an intake to lower the reservoir water level before the flood comes. Implementation of early release on reservoir routing requires an initial elevation that is different from the initial elevation in general. The aim of this research is to determine the new initial elevation to support early release operations for the Sadawarna Reservoir. This research was conducted by calculating return flood discharge and flood routing in reservoir with 3 (three) scenarios of initial elevation. The method used for analysis of return flood discharge is SCS (Soil Conservation Service). The reservoir routing method uses level pool routing with the HEC-HMS application. Initial elevation is determined by 3 (three) scenarios that started from initial elevation +75,25 masl, +77,00 masl, and +78,50 masl. The results of 3 (three) scenarios showed that the optimal initial elevation that can be used in early release operations is at an elevation of +77,00 masl. The results of the reservoir flood routing simulation with initial elevation resulted reduction flood discharge up to return period of 50 years and resulted in the fastest reservoir water level recovery

Real-time regulation of detention ponds via feedback control: Balancing flood mitigation and water quality

Detention ponds can mitigate flooding and improve water quality by allowing the settlement of pollutants. Typically, they are operated with fully open orifices and weirs (i.e., passive control). Active controls can improve the performance of these systems: orifices can be retrofitted with controlled valves, and spillways can have controllable gates. The real-time optimal operation of its hydraulic devices can be achieved with techniques such as Model Predictive Control (MPC). A distributed quasi-2D hydrologic-hydrodynamic coupled with a reservoir flood routing model is developed and integrated with an MPC algorithm to estimate the operation of valves and movable gates in real-time. The control optimization problem is adapted to switch from a flood-related algorithm focusing on mitigating floods to a heuristic objective function that aims to increase the detention time when no inflow hydrographs are predicted. The case studies show the potential results of applying the methods developed in a catchment in Sao Paulo, Brazil. The performance of MPC compared to alternatives that do not change the operation over time with either fully or partially open valves and gates are tested. Comparisons with HEC-RAS 2D indicate volume and peak flow errors of approximately 1.4% and 0.91% for the watershed module. Simulating two consecutive 10-year storms shows that the MPC strategy can achieve peak flow reductions of 79%. In contrast, the passive scenario has nearly half of the performance (41%). A 1-year continuous simulation results show that the passive scenario with 25% of the valves opened can treat 12% more runoff compared to the developed MPC approach, with an average detention time of approximately 6 h. For the MPC approach, the average detention time is nearly 14 h, indicating that both control techniques can treat similar volumes; however, the proxy water quality for the MPC approach is enhanced due to the longer detention times achieved.

Cascade failure risk analysis of mixed reservoirs based on disaster spreading theory

The reservoirs in the basin are connected in series or in parallel, forming a mixed reservoir group. Failure of a single dam in a mixed reservoir group may lead to subsequent failures of downstream dams, resulting in a cascading failure of the reservoir group. However, existing studies mainly focus on the impact of the upstream dam failure on the downstream dams, and lack a comprehensive consideration of the risk level of the upstream dams, the dam's own risk, and its own warning and flood release capacity. This limitation affects the accuracy of the actual risk calculation results of mixed reservoir dams. In this paper, the cascading failure risk chain is determined using graph theory, and a cascade failure risk analysis model based on disaster spreading theory is developed by combining dam break flood simulation and reservoir flood routing theory. The cascade failure risk is assessed in terms of the probability and the duration of a cascading failure. The model is applied to six mixed reservoirs in the Wujiang River Basin, China. The sensitivity of the model parameters is analyzed by examining a specific node, and the feasibility and effectiveness of the model are verified.

Flood Control Rule in Bintang Bano Reservoir

Flood is a disaster that occur since ancient times until now, and even in the future. Flood can be caused by nature, humans, or both. Constructing new dams are a good method to reduce flood and losses caused by floods, one of them is Bintang Bano Dam. The purpose of this study is to analyze the capacity of the gated spillway and ungated spillway, so that the allowable return period of discharge can be estimated through the both spillways. This research activity divided into 4 (four) stages are: the identification and data processing stage, the rainfall-runoff modeling stage, the reservoir flood routing, and the simulation of the operation of opening gates on both spillways. The gated spillway can be operated at all return periods (2 years to PMF). Ungated spillway can only overflow discharge with ≥ 100 years return period. During the return period 2 years to 50 years, no runoff occurs through the ungated spillway. For the return period of 100 years to 1000 years there is runoff through the ungated spillway without any gate openings. It is recommended for floods with a return period of 2 years to 50 years, with upstream and downstream conditions of rainfall, the gate can be closed. But for floods with 100 years to 1000 years return periods, the discharge automatically overflows through the ungated spillway cannot be opened/damaged.

The Impact of Dam Reservoir on Flood Reduction (Case Study Logung Reservoir, Kudus, Central Java)

The Indonesian government targeted building 65 reservoirs and dams in 2015-2022. The purpose is to maintain food security facing the long-term climate crisis, besides reducing the impact of a flood. Logung Reservoir is located on the Logung River, Kudus, Central Java. This earth-fill dam was built to solve the flood and drought problems in Kudus. However, the existence of the Logung Reservoir gives a risk to the downsteam area. The purpose of this research is to study flood reduction and the risk of overtopping, which can cause a dam break, and to calculate the Logung Reservoir spillway's performance in handling floods. This study is based on four main steps: the rainfal-runoff modelling, the extreme rainfall estimation, the hydrograph inflow of the dam estimation, and the evaluation of food reduction. The results of the 1000-year rainfall analysis and PMP for the Logung dam basin were 409 mm and 704 mm, respectively. Rainfall distribution is made using ABM, and effective rainfall is calculated by the SCS method. Land use analysis in the Logung dam watershed obtained a CN-II of 71.4 and a CN-III of 85.2. The rainfall-runoff transformation method used a unit hydrograph. The Nakayasu and Gama-I unit hydrographs show significant differences from the peak discharge, although not for the time base. The flood hydrograph design affects the reservoir performance. The reservoir flood routing results a dumping efficiency of 35% for the 1000-year and 21% for PMF. The 1000-year flood routing shows that there was no risk of overtopping. The highest water level on the PMF flood routing at +94.1. Several solutions can prevent overtopping by reducing inflow discharge through small dams upstream, increasing the green area, or modifying spillway structure.

Reservoir Flood Routing Simulation for Dam Safety Management in Thailand

A reservoir flood routing simulation software with spillway operation rules that are readable and configurable by the spillway operator is developed in this study. The software is part of the Dam Safety Remote Monitoring System used by the Electricity Generating Authority of Thailand. The flood routing simulation is implemented using a storage-indication routing method, which is a hydrologic method. The spillway operation rules are exhibited in a tree-based structure, in which the spillway gate opening is derived from the current reservoir water level (RWL), spillway gate opening, and flood situation if the peak inflow has passed. The simulation results show that the simulated RWL is similar to the RWL data in the dam construction manual. This verifies the accuracy of the reservoir flood routing simulation, which is useful for planning the spillway operation.

Discussion on Nonlinear Behaviors in Reservoir Flood Routing Modeling and Derived Uncertainties

In existing studies, external factors, such as hydrologic, hydraulic, and decision-making uncertainties, have been widely recognized as major risk source in reservoir flood routing. There are few researches focused on the intrinsic uncertainties which rooted in the reservoir flood routing modeling, for instance, the sensitivity of the water level to the initial condition in the passage of flood routing. The governing equation of the reservoir flooding routing is a first-order Ordinary Differential Equation, which can be simplified as a water balance equation. A deterministic mathematical model can be set up by combining the governing equation with the flood operating rules and the water level-storage relationship functions of reservoirs. As far as the deterministic model is concerned, nonlinear behaviors and their characteristics in different stages of flood routing were discussed for the reservoir with multistage operating rule by simulations in this paper. The results showed that the state variables (i.e., water level and discharge rate) of the system are not sensitive to initial small perturbations in the free overflow stage. However, in the confined outflow stage, which usually appears in segmented flood operating rules designed for multi-purpose flood control, a small initial disturbance can grow gradually over time with the evolution of the system, as a result, a large deviation of the water level and discharge rate of the reservoir could developed at the end of the simulation. Additionally, some case studies were conducted in this paper to demonstrate this nonlinear response of flood routing to the initial disturbance. Although the nonlinear behaviors in reservoir flood routing are still subject to further study, once again, it proves that uncertainties appear there indeed in a deterministic system according to this research. The results of this paper indicate that the nonlinear responses and the corresponding uncertainties rooted in it may have to be considered deliberately in different stages of flood routing, because this could has potential impacts not only on reservoir flood control but also on the reliability of the risk assessment.

Real-time reservoir flood control operation for cascade reservoirs using a two-stage flood risk analysis method

The real-time operation of multi-reservoir systems is a vital issue in the field of reservoir management. The uncertainty caused by inflow forecasting means that risk analysis is necessary for such real-time operation. However, differences in the length of the forecast periods for different reservoirs in the system are seldom considered in the risk analysis of multi-reservoir systems. This paper presents a two-stage flood risk analysis method of multi-reservoir systems that takes the differences in the length of forecast lead-times into consideration. The aim of the proposed method is to evaluate the uncertainty of the flood forecasting by dividing the operation horizon into the forecast lead-time and the beyond-forecast time period. The risk within the forecast lead-time is estimated by counting the frequency of failure numbers among all scenarios with the help of the scenario-based forecasts. The risk beyond the forecast time period is determined using reservoir flood routing with the design flood hydrographs, which are selected according to the differences in the length of the forecast periods between any two reservoirs. The proposed two-stage risk analysis method is verified using stochastic simulations method based on Monte Carlo sampling. A real-time flood control operation model is established by taking the proposed two-stage risk analysis method as a constraint. China’s Ankang-Danjiangkou Cascade Reservoirs are considered as a case study, and the results indicate that the proposed real-time operation model can increase hydropower generation by 0.22 billion kWh during the summer flood season without increasing the flood risk in the multi-reservoir system. The proposed method enhances our understanding of risk management for the real-time flood control operations in multi-reservoir systems.

Impact of managed aquifer recharge structure on river flow regimes in arid and semi-arid climates

Managed aquifer recharge (MAR) structure is widely used to expand groundwater resources. In arid regions with flash flooding, MAR can also be used as a flood control structure to decrease peak discharge of rivers. In this paper, we present a method for quantifying the role of MAR in head water systems and assess its impact on the total water balance in a river basin. The method is based on rainfall-runoff modeling, reservoir flood routing, recharge analysis and river flow analysis. For the case selected, Kamal Abad MAR in Lake Maharlou basin in southern Iran, we analyzed changes in the downstream river regime using two scenarios (with MAR and without MAR) with different return periods. The results revealed a significant impact of MAR on river flow in terms of changes in flow timing, magnitude and variability. With MAR, the ephemeral river studied became disconnected from the main stream, albeit, whereas the case without MAR, floods with return period higher than 10 years would be connected to the downstream. Even though, MAR structures are useful in arid and semi-arid climates for irrigation water supply, their placing and designing need more attention. The developed method can be used to assess the impacts of MAR on river flow and find the best location for it to make the connection of the ephemeral river and downstream river, an issue which has not received much attention in hydrological research.

Incorporating reservoir impacts into flood frequency distribution functions

Assessing flood frequency is pivotal for hydrology, with implications for many fields ranging from river science to the insurance industry. Reservoir regulation may alter the characteristics of the flood frequency distribution function. This paper incorporates reservoir impacts as an inherent variable to derive an analytical solution of outflow peaks and proposes new flood frequency distributions. Steps are as follows: (1) the original flood without reservoir impacts is assumed to follow a Pearson type III distribution, (2) linear and nonlinear reservoir models, including numerical integration and triangular area calculation methods, are proposed to simulate the relationships between inflow and outflow peaks, and (3) the flood frequency distributions resulting from reservoir impacts are derived. Derived equations are applied to the Shuibuya and Wuqiangxi reservoirs in China. Results show that: (1) although the numerical integration method with the nonlinear model is comparable with the reservoir flood routing, the triangle area calculation method with the nonlinear model is recommended for its accuracy and simplicity, (2) the reservoir regulation changes the flood frequency distribution function entirely in the nonlinear reservoir model, while only change the parameter in the linear reservoir model, and (3) downstream flood’s CV can be increased or decreased, which depends on the reservoir regulating capacity. It is indicated that altering the parameters of the flood frequency distribution is not sufficient to characterize watershed under reservoir control. This paper proposes the analytical solution about inflow and outflow peaks, which can point out the possible changes in the watershed with reservoir construction in plan.

Integrated Simulation of Spillway and Diversion Structure in Flood Risk Assessment of Upper Solo River

Wonogiri Reservoir is a multi-purpose hydraulic structure that is used for water supply service and flood control in the watershed area of Upper Solo River. Inflow of the Wonogiri Reservoir comes from 10 rivers in the watershed’s catchment area. As for the purpose of reservoir’s sediment controller, a new spillway is constructed; and also closure dike is being built, which influenced the change on reservoir storage characteristic, and then means that a new reservoir operation guideline is necessary. Therefore, study on flood routing on the watershed of Upper Solo River at the new condition of the reservoir operation is needed. The analysis was conducted to acquire detailed information on flood characteristics of Wonogiri Reservoir and Upper Solo River started from the downstream of the reservoir until the downstream control point in the Jurug Water Level Recorder including the flood discharge and the maximum water level. The analysis procedure was performed by four components, which are flood forecasting, reservoir flood routing, rainfall-runoff lateral inflow, and hydraulic channel routing. The analysis result was integrated into a software package which was arranged by using the Microsoft Visual Studio Express 2012, Microsoft Access, and HEC-RAS. With the support of the software, it was expected that the decision making in the spillway operational is more quickly and more accurate (rapid assessment) in order to improve the flood control performance in the area of Upper Solo River.

Modern Optimization Methods in Water Resources Planning, Engineering and Management

Mathematical (analytical, numerical and optimization) models are employed in many disciplines including the water resources planning, engineering and management. These models can vary from a simple black-box model to a sophisticated distributed physics-based model. Recently, development and employment of modern optimization methods (MOMs) have become popular in the area of mathematical modeling. This paper overviews the MOMs based on the evolutionary search which were developed over mostly the last 30 years. These methods have wide application in practice from finance to engineering and this paper focuses mostly on the applications in the area of water resources planning, engineering and management. Although there are numerous optimization algorithms, the paper outlines the ones that have been widely employed especially in the last three decades; such as the Genetic Algorithm (GA), Ant Colony (AC), Differential Evolution (DE), Particle Swarm (PS), Harmony Search (HS), Genetic Programming (GP), and Gene Expression Programming (GEP). The paper briefly introduces theoretical background of each algorithm and its applications and discusses the merits and, if any, shortcomings. The wide spectrum of applications include, but not limited to, flood control and mitigation, reservoir operation, irrigation, flood routing, river training, flow velocity, rainfall-runoff processes, sediment transport, groundwater management, water quality, hydropower, dispersion, and aquifers.

Risk Analysis of Reservoir Flood Routing Calculation Based on Inflow Forecast Uncertainty

Possible risks in reservoir flood control and regulation cannot be objectively assessed by deterministic flood forecasts, resulting in the probability of reservoir failure. We demonstrated a risk analysis of reservoir flood routing calculation accounting for inflow forecast uncertainty in a sub-basin of Huaihe River, China. The Xinanjiang model was used to provide deterministic flood forecasts, and was combined with the Hydrologic Uncertainty Processor (HUP) to quantify reservoir inflow uncertainty in the probability density function (PDF) form. Furthermore, the PDFs of reservoir water level (RWL) and the risk rate of RWL exceeding a defined safety control level could be obtained. Results suggested that the median forecast (50th percentiles) of HUP showed better agreement with observed inflows than the Xinanjiang model did in terms of the performance measures of flood process, peak, and volume. In addition, most observations (77.2%) were bracketed by the uncertainty band of 90% confidence interval, with some small exceptions of high flows. Results proved that this framework of risk analysis could provide not only the deterministic forecasts of inflow and RWL, but also the fundamental uncertainty information (e.g., 90% confidence band) for the reservoir flood routing calculation.

Streamflow Forecast Errors and Their Impacts on Forecast-based Reservoir Flood Control

To make full use of water captured by reservoirs in flood seasons, methods such as forecast-based reservoir flood control (i.e., reservoir operation during flood periods based on precipitation or inflow forecasts) have been developed in China in the past few decades. The success of forecast-based reservoir flood control depends heavily on the precision of the precipitation or inflow forecasts. This study analyzes the sources of uncertainty and quantifies it in the process of reservoir flood control based on forecasts. First, flood inflow series is regarded as a random process with the forecasted flood inflows as its expectation process; the flood inflow error series, which is the difference between the observed inflow process and the forecasted inflow process, is obtained according to the statistical characteristics of the flood forecasts. Second, reservoir flood routing simulations are carried out using the Monte Carlo method with the flood inflow error series as an input to obtain output water level and discharge series. Finally, the frequency distributions of the maximum water level (MWL) reached during the passage of floods are used to evaluate the uncertainties and the corresponding risks associated with forecast-based flood control. These uncertainties and risks are what the operators of the reservoirs care about the most.

Risk Analysis for Real-Time Flood Control Operation of a Reservoir

AbstractThere are many uncertainties in real-time flood control operation of a reservoir, which create risks in flood control decision making. In this paper, three uncertainty factors—reservoir inflow-forecasting errors, outflow errors, and observation errors of reservoir storage capacity curve—are taken into account and quantified methods are proposed. With consideration of the three uncertainties and correlation between inflow-forecasting errors, reservoir water-level errors are derived using the stochastic differential equation of reservoir flood routing. Then the definition and calculation methods for flood risk at each moment and the integrated risk of the entire flood process are proposed. The Dahuofang reservoir in China is selected as the case study. The results shows that the risk resulting from the uncertainties is decreased by the reservoir flood regulation function and that the proposed method can provide a useful way to estimate the risks in real-time reservoir flood control.

Reservoir Flood Routing Considering the Non-Stationarity of Flood Series in North China

Owing to the increasing anthropogenic activities, flood frequency analysis and flood control scheduling of reservoir become more and more complicated because of the non-stationarity of flood series. This paper aims to assess the effects that non-stationary flood series, which is affected by land use change of Daqing River Basin (in North China), has induced on the reservoir flood routing. And the analysis has been carried out in Xidayang Reservoir, which is located in south branch of Daqing River Basin of North China. In this paper, the annual maximum peak discharge series and the annual maximum flood volume (1-day, 3-day and 6-day) series of Xidayang Reservoir were selected to detect their variation using three steps change point diagnosis. Mixed distribution was employed to fit the non-stationary flood series, estimating parameters by simulated annealing algorithm. The results indicate that (1) mixed distribution provided a more appropriate and superior fit than conventional distribution (P3 distribution) to non-stationary flood series, (2) design flood values estimated by mixed distribution reduced by 0.03 %–20.24 % with different return periods compared with the results computed by conventional P3 distribution, and (3) through reservoir flood routing, the maximum water level and maximum discharge with various return periods considering the series’ non-stationarity also showed a decrease by up to 0.56 m and 81.68 % respectively compared with the results regardless of the series’ non-stationarity. These results provide a significant theoretical basis for flood control and water resources management in Daqing River Basin.

Estimation of reservoir flood control operation risks with considering inflow forecasting errors

A method for quantifying inflow forecasting errors and their impact on reservoir flood control operations is proposed. This approach requires the identification of the probability distributions and uncertainty transfer scheme for the inflow forecasting errors. Accordingly, the probability distributions of the errors are inferred through deducing the relationship between its standard deviation and the forecasting accuracy quantified by the Nash–Sutcliffe efficiency coefficient. The traditional deterministic flood routing process is treated as a diffusion stochastic process. The diffusion coefficient is related to the forecasting accuracy, through which the forecasting errors are indirectly related to the sources of reservoir operation risks. The associated risks are derived by solving the stochastic differential equation of reservoir flood routing via the forward Euler method. The Geheyan reservoir in China is selected as a case study. The hydrological forecasting model for this basin is established and verified. The flood control operation risks in the forecast-based pre-release operation mode for different forecasting accuracies are estimated by the proposed approach. Application results show that the proposed method can provide a useful tool for reservoir operation risk estimation and management.

Derivation of Reservoir’s Area-Capacity Equations

Area-capacity curves are usually used for reservoir flood routing, reservoir operation, determination of water surface area, and capacity corresponding to each elevation, reservoir classification, and reservoir sediment distribution. In this study, the similarity between the natural logarithmic function curve and the reservoir capacity curve is used to obtain the mathematical equation for dimensionless capacity curve. The obtained equation has only one unknown dimensionless parameter, named the “reservoir coefficient” N . If the obtained dimensionless capacity equation is plotted on a log-log paper, for any values of N , it will be approximately a straight line and the reciprocal of the line slope will be equal to the reservoir shape factor. The reservoir area equation and equation of reservoir coefficient are obtained by differentiating the reservoir capacity equation. Also, more precise values of N for the area and capacity equations can be obtained by using the least-squares method. The obtained equati...

Numerical Solution to Reservoir Flood Routing

Floods spreading through reservoir spillways are usually generalized into a first-order nonlinear ordinary differential equation in engineering. With the classical Runge–Kutta–Fehlberg (RKF) method, ignoring the local stability of the numerical solution, a Runge–Kutta–Fehlberg–Reverse (RKFR) method is advanced and employed to route reservoir floods. In the improved method the step length will further be rectified following the RKF using a local stability parameter, which is based on the fact that as the local truncation error is small enough, the local stability might be approximately characterized by the relative error between the initial dependent variable associated with every step and the feedback that may be calculated through a Runge–Kutta (RK) method. The method presented is first verified with two numerical examples, and the results are more accurate and stable with comparable computed speed compared with the RKF method. Subsequently, the RKFR is coupled with the reservoir flood routing program, a...

Point Slope Approach for Reservoir Flood Routing

The point-slope method of routing floods through reservoirs uses equations and criteria for determining the outflow hydrograph slope and the inflection point of the rising limb of the outflow hydrograph on the basis of the inflow hydrograph, the topography of the reservoir, and the hydraulic characteristics of the outflow structure. The point-slope method is less broadly applicable than the traditional incremental-time methods, but within its limitations (simple single-peaked inflow hydrographs), it is fast, accurate, and adaptable for investigating alternate designs. A check and adjustment procedure provides assurance that the result is valid. This procedure and the criteria for determining the inflection point of the outflow hydrography are of general applicability with reservoir flood routing methods.