Dissertation for obtaining a master's degree
in the field of civil engineering/water engineering
Winter 1392
1-1- Introduction
In this chapter, an overview of the concept of climate change and its causes and the impact of this phenomenon on natural resources and water resources is made, and then the necessity and purpose of this study is mentioned.
1-2- The concept of climate change and the importance of investigating dam reservoir management
Climate change is the change in the climate behavior of a region compared to the behavior that is expected during a long-term time horizon from the information observed or recorded in that region. Climate change is a complex atmospheric-oceanic phenomenon on a global and long-term scale. This phenomenon is affected by the increase of greenhouse gases in the atmosphere, which leads to a change in the climate, a change in the spatial and temporal distribution of precipitation and its type (solid or liquid), surface water flow, evaporation, feeding the underground water table and water quality, and generally causes a new trend in the global climate. Climate change causes some areas to become wetter and some areas to become drier and increase the intensity and frequency of extreme events such as floods and droughts. In general, the temporal and spatial distribution of precipitation and its patterns have changed and the amount of evaporation also increases. Without a doubt, climate change is one of the most important challenges of the current weather and climate era, which occurs on a global scale and has important effects on countries, especially in the water resources sector (IPCC, 2001). Greenhouse gases, especially CO2. The increasing emission of greenhouse gases disrupts the earth's energy balance and causes global warming. The phenomenon of global warming and climate change resulting from it has significant effects on various systems such as water resources, agriculture and environment. The changes resulting from the rapid economic and industrial growth, on the one hand, and the transition of many third world countries to the industrial society in the 1970s and 1980s, on the other hand, have caused the spread of environmental changes. Although the rapid improvement in the technology of industrial goods and the development of appropriate laws in the preservation and control of the environment and healthy water have gradually provided the ground for the reduction of pollutants effective in climate change, direct measurements of carbon dioxide, carbon monoxide, methane and the reduction of ozone concentration during the past three to four decades have provided a worrying picture of environmental degradation and climate anomalies (Baede et al., 2001).
According to the IPCC reports, if the emission of greenhouse gases is not reduced, the average temperature of the earth can increase by 1.1 to 4.6 degrees Celsius by the year 2100. Also, studies show the rise of sea levels, the melting of polar ice caps, the reduction of snow cover and the increase of extreme climatic phenomena such as floods and droughts, which have occurred as a result of the average increase in the surface temperature of the Earth (IPCC, 2007). Economic, social and environmental issues were raised. Climate change will not only have direct effects on the living environment in general, but also cause the data and information collected in the past, which are the basis for the design of water structures and other structures, to no longer be a reliable indicator for measuring the behavior of water resources and the importance of the structure in the future (Lane et al., 1999).
Until the last two decades, most of the experts and specialists of the water industry in the world used their efforts to achieve the techniques of building water structures, and most of the projects led to the construction of dams and water transmission and distribution networks. In this regard, extensive research was conducted, which led to the preparation of international standards.
Although the technology of building a water structure and its appendices plays an important role in increasing the efficiency of the project in a water resources system [1], it is not able to manage that system alone.
Since 1980, after crossing the border of the construction of water facilities in most countries of the world, due to the emergence of various issues such as the increase in water demand, the occurrence of severe floods and droughts, and especially the environmental issues, pollution and climate change, the management of water resources has become an important issue at the forefront of research and studies.
The management of water resources, especially from a mathematical point of view, has led to valuable achievements in recent years due to extensive research in this field. Although the connection between research and executive centers or from theory to application of research is not easily possible, nevertheless, after years of trying to connect the two, water resources management is currently being done using new tools and methods.
One of the discussions in the management of water resources, especially in countries that have a large number of reservoir dams, is related to the management of the reservoirs of the dams.
In Iran, with more than 80 dams in operation and dozens of dams under study, in most cases it is observed that the volume of water stored behind the dam is far less than the design volume.
The limitations of the rivers that are constantly flooded and the lack of a coherent watershed management system require rational, principled and realistic management in the exploitation of dams.
In this regard, by using advanced techniques and sciences and tools such as satellite systems, geographic information, data banks, and new computing methods, a system can be created by which the dam manager can evaluate the condition of the dam at any moment according to the results of the system and make the appropriate decision [2] for better management. (3)
Optimum exploitation[3] of reservoirs of dams requires management in storage areas that are predicted for future inflows. Optimization [4] is a basic concept for increasing the management and efficiency of mutual effects [5] of dam construction projects. The concept of optimal exploitation became more important when the rules of exploitation[6] of reservoirs became more complete.
Optimizing production requires effective software to predict inflows to reservoirs, from deterministic real-time forecasts to long-term probabilistic forecasts. These softwares should also provide guidelines (operational rules) to make operational decisions, provide (65)
Reservoir operation rules are guidelines for reservoir operation officials. These rules apply to reservoirs that are being used in permanent conditions (and not for reservoirs that are filled immediately after construction or are used to provide a set of temporary new goals).
The rules of exploitation of reservoirs are actually the transfer of information from the designer to the operators of exploitation, which must be frequently updated [7]. There are several types of rules, but each refers to the desired or necessary storage or output volume of the reservoir at any particular time of the year. Some of these rules determine the desired storage volumes, which are referred to as command curves [8]. (18)
A command curve describes how much storage should be in the reservoir at different times of the year so that we can supply the required water all the time or with minimal shortage.
Reservoir management using command curves is a complex matter, because these curves are derived from a precise series of flows that may not occur again.
The exploitation of dams is sometimes limited only to water supply management [10], but water shortage occurs when the demand [11] of water exceeds its supply [12], so in water optimization management plans, both of them should be calculated.