Imprecise probabilistic estimation of design floods with epistemic uncertainties

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.An imprecise probabilistic framework for design flood estimation is proposed on the basis of the Dempster-Shafer theory to handle different epistemic uncertainties from data, probability distribution functions and probability distribution parameters. These uncertainties are incorporated in cost-benefit analysis to generate the lower and upper bounds of the total cost for flood control, thus presenting improved information for decision making on design floods. Within the total cost bounds, a new robustness criterion is proposed to select a design flood that can tolerate higher levels of uncertainty. A variance decomposition approach is used to quantify individual and interactive impacts of the uncertainty sources on total cost. Results from three case studies, with 127-, 104- and 54-year flood data sets respectively, show that the imprecise probabilistic approach effectively combines aleatory and epistemic uncertainties from the various sources and provides upper and lower bounds of the total cost. Between the total cost and the robustness of design floods, a clear trade-off which is beyond the information that can be provided by the conventional minimum cost criterion is identified. The interactions among data, distributions and parameters have a much higher contribution than parameters to the estimate of the total cost. It is found that the contributions of the various uncertainty sources and their interactions vary with different flood magnitude, but remain roughly the same with different return periods. This study demonstrates that the proposed methodology can effectively incorporate epistemic uncertainties in cost-benefit analysis of design floods.This study was supported by the National Natural Science Foundation of China (Grant No. 51320105010 and 51279021). The first author gratefully acknowledges the financial support provided by the China Scholarship Council. The authors are deeply indebted to editors, Dr Francesco Serinaldi and another anonymous reviewer for their valuable time and constructive suggestions that greatly improved the quality of this paper. The data of Three Gorges were obtained from the China Three Gorges Corporation. The data of Biliu were obtained from the Biliu reservoir administration. The data of Harbin were obtained from the Harbin hydrology bureau. These data are available as in Supporting Information Data Set which includes Data Set S1, Data Set S2 and Data Set S3. Data Set S1 corresponds to Three Gorges; Data Set S2 corresponds to Biliu; Data Set S3 corresponds to Harbin

System Dynamics Modeling of Multipurpose Reservoir Operation

System dynamics, a feedback – based object – oriented simulation approach, not only represents complex dynamic systemic systems in a realistic way but also allows the involvement of end users in model development to increase their confidence in modeling process. The increased speed of model development, the possibility of group model development, the effective communication of model results, and the trust developed in the model due to user participation are the main strengths of this approach. The ease of model modification in response to changes in the system and the ability to perform sensitivity analysis make this approach more attractive compared with systems analysis techniques for modeling water management systems. In this study, a system dynamics model was developed for the Zayandehrud basin in central Iran. This model contains river basin, dam reservoir, plains, irrigation systems, and groundwater. Current operation rule is conjunctive use of ground and surface water. Allocation factor for each irrigation system is computed based on the feedback from groundwater storage in its zone. Deficit water is extracted from groundwater.The results show that applying better rules can not only satisfy all demands such as Gawkhuni swamp environmental demand, but it can also  prevent groundwater level drawdown in future

River Stream-Flow and Zayanderoud Reservoir Operation Modeling Using the Fuzzy Inference System

The Zayanderoud basin is located in the central plateau of Iran. As a result of population increase and agricultural and industrial developments, water demand on this basin has increased extensively. Given the importance of reservoir operation in water resource and management studies, the performance of fuzzy inference system (FIS) for Zayanderoud reservoir operation is investigated in this paper. The model of operation consists of two parts. In the first part, the seasonal river stream-flow is forecasted using the fuzzy rule-based system. The southern oscillated index, rain, snow, and discharge are inputs of the model and the seasonal river stream-flow its output. In the second part, the operation model is constructed. The amount of releases is first optimized by a nonlinear optimization model and then the rule curves are extracted using the fuzzy inference system. This model operates on an "if-then" principle, where the "if" is a vector of fuzzy permits and "then" is the fuzzy result. The reservoir storage capacity, inflow, demand, and year condition factor are used as permits. Monthly release is taken as the consequence. The Zayanderoud basin is investigated as a case study. Different performance indices such as reliability, resiliency, and vulnerability are calculated. According to results, FIS works more effectively than the traditional reservoir operation methods such as standard operation policy (SOP) or linear regression

A System Dynamics- Based Analysis of Operation Policies for Water Resources at River Basin Scale

There are many natural and human subsystems in a watershed with their special interrelationships. These interrelationships must be duly considered for the integrated and comprehensive management of the water resources in a water basin. One example of such interrelationships includes upstream water development and utilization projects which adversely affect downstream water quality and quantity. Within the framework of an integrated water resources management, various water resources development and operation policies must be analyzed to select the most convenient one securing the benefits of all the stakeholders in the watershed. In this study, various operation policies in theUrmiahLakeBasinand theAjiChaiRiverBasin on the east of the lake are analyzed to determine their impacts on the water level in the lake. For this purpose, the Aji Chai Basin is subdivided into three sub-basins and the System Dynamics, which is a feedback–based object–oriented simulation approach, is used to develop the dynamic model of the region. To investigate the present scenarios, the ARMA (1, 1) model is used to generate 10 different time series for each sub-basin and the lake water level is accordingly determined for each case

System Dynamic Model in Tehran Urban Water Management

Water management needs to decide for the water resources development project and future planning based on comprehensive and integrated views. One of the management tools is based on system dynamic approach. This technique has the capability of simulating complex water resource systems to support decision making. The undefined outcome of decisions is revealed through this methodology. The main objective of this method of simulation is its simplicity and rapid learning of system behaivior in present and future conditions. In this paper, the model for water resources and urban water demand was developed with dynamic system for evaluating the trend of resources and demands and the effective parameter on them. The feedback of urban water resources due to the economic, socio and environmental aspects of supply and demand brings about a complex system which can only be analyzed through integrated and dynamic views of the system. The results of the dynamic analysis ofTehranurban water system leads to a tool for understanding and visualizing the reasons of the shortages. This model showes the trend of water balance variation in future as well as the effect of management scenario such as interbasin water transfer, collection and treatment of waste water and demand management

Assessment of Residential Water Conservation due to Using Low-Flow Fixtures

Increasing population and socioeconomic development have led to increased urban water demand. Residential use forms the principal portion of urban water consumption. One of the most effective residential water conservation measures is using low-flow fixtures and devices designed for this purpose. In this paper, conservation results of using low-flow fixtures including low-flow showerheads and faucet aerators are evaluated in the city of Kashan. For this purpose, two groups of 40 households were randomly selected as experimental and control groups. The fixtures were installed in the houses of the experimental group and water consumption was measured over one month. Results indicate that retrofitting with these fixtures reduces residential water consumption by about 22 percent. Projections of Kashan’s future water demand and supply indicate that using these fixtures by Kashan residents can delay the need for new water supply projects by up to 6 years. Cost-benefit ratio of this conservation measure for Kashan is estimated to be 5.8 to 1. Finally, user satisfaction of retrofitting with these fixtures is evaluated

Conflict Resolution of Water Resources Allocations Using the Game Theoretic Approach: The Case of Orumieh River Basin

During recent years, unavoidable consequences of increased demand for, and decreased supply of, various natural resources, especially water, have caused increased conflict over their exploitation and also allocation to different stakeholders. Water allocations merely based on a water rights approach usually do not make efficient use of water for the whole river basin. Thus, there is a need for a comprehensive and stable allocation method that can satisfy all involved interest groups in the best manner. One of these methods is game theory that can be used to allocate the water resources among riparian parties regarding principles of equity, efficiency and sustainability. In this study, first a comprehensive linear programming model has been developed to achieve the optimal allocation pattern based on the initial water rights of stakeholders. Then, by using the results of the water planning model combined with the game theoretical concepts  such as the Core, the Shapely Value, and, the Gately propensity to disrupt index, possible cases of cooperation among riparian parties have been evaluated. Finally, through the case study of the Orumieh River Basin in Iran with scarce water resources and multiple users, effectiveness and potential advantages of this approach have been shown. The results of the optimization model showed that the Kordestan province has the best situation in supplying its demands relative to the other provinces and in contrast, the East Azarbayejan has the most deficiency in supplying its demands in both agriculture and environmental sectors. Moreover, by following the given allocation pattern, the amount of water entering the Lake Orumieh will be more than its environmental demand during the planning. Therefore, the results of this study showed that cooperative game theory can be applied successfully to assess the cases of cooperation in the Orumieh River Basin in conjunction with a comprehensive water planning model

Urban Water Management Considering Reclaimed Wastewater and Runoff as a New Water Resource for City of Tehran, Iran

Tehran, the capital of Iran, like many megacities in the world is faced with increasing freshwater demand and water resources limitation due to the rapid growth of population. In this paper, water reuse and wastewater recycling are considered as a sustainable solution for water supply and wastewater management of Tehran. A linear programming optimization model with the object of cost minimization is used to allocate water between users and resources, concerning the water quantity and quality of each one. Ultimately the economic and environmental effects of this strategy will be presented as the conclusion of this study. According to this study, improving wastewater treatment plants and control of water quality in canals and streams in order to substitute these two new resource for freshwater and groundwater have positive environmental and economic effects. The examples of environmental benefits are reducing pollution loads to receiving streams, adjusting increasing water demand and preventing groundwater level drawdown especially in the period of drought. In addition to the environmental benefits, although improving wastewater treatment plants and control of water quality in canals and streams need considerable investments, long usage of these two new recourses is more worthwhile

Climate Change And Hydropower Planning In The Middle East: Implications For Iran\u27S Karkheh Hydropower Systems

Given the important role of hydropower in peak electricity management, Middle Eastern countries are actively pursuing development of more hydropower resources by construction of large dams. Nonetheless, climate change is expected to affect the future productivity of hydropower by influencing the hydrologic cycle and different climate variables in the region. Although reactive plans to minimize climate change impacts on hydropower production have been implemented in the developed world, the developing world can still benefit from proactive actions. Studies of climate change impacts before and during implementation of hydropower projects can result in timely responses and adaptation to climate change with a potential of considerable cost savings. This study investigates the potential impacts of climate change on the hydropower systems in the Karkheh River Basin - the third largest river basin in Iran - in terms of potential for hydroelectricity generation. A simulation model is developed to examine how hydropower generation levels vary for different future climate change scenarios in this representative Middle Eastern basin. The obtained results suggest that the existing operation rules and design specifications, developed based on the historical climatic conditions, can lead to inefficient operations of the hydropower in the basin. Because of insignificant streamflow reductions in the short term, hydropower production may not change considerably in the near future. However, a serious hydropower generation deficit is expected in the midterm and long-term horizons in the Karkheh River Basin. Therefore, adaptation to the future climate change conditions and revision of the operation rule curves and design specifications are essential to optimal hydropower operations in this basin. © 2013 American Society of Civil Engineers