View with images and charts Determining The Capacity Of Dam Using Probabilistic Approach. Chapter One Prelude 1.1 Introduction Dam, barrier, commonly across a watercourse, to hold back water, often forming a reservoir or lake; dams are also sometimes used to control or contain rockslides, mudflows, and the like in regions where these are common. According to the definition given by Federal Emergency Management Agency (FEMA), “Dam means an artificial barrier, including dikes (a barrier blocking a passage, especially for protection), embankments, and appurtenant works- that impounds, diverts, water or is designed to impound or divert water or a combination of water and any other liquid or material in the water”.1 Important structure or machinery incident to or annexed to a dam that is built to operate and maintain a dam is called the appurtenant structure. Important appurtenant structures of a dam may include spillways- to allow safe passage of flood flows, tunnels- to control releases for irrigation and / or power generation, power station, and canal outlet (s). Spillway means water in or about a dam, designed for the discharge of water. Impoundment means the water held back by a dam. Dams are made of timber, rock, earth, masonry, or concrete or of combinations of these materials. The height of a dam may vary from less than 50 feet to more than 1,000 feet. The reservoir or lake created by a dam may also vary in size; its area may vary from a few acres to more than 100 square miles. In a dam, water arrives which is termed as input, and water is stored in the associated reservoir for some time. Then a fraction of water stored is released from the dam to meet the demand. The ‘release’ is usually called ‘draft’. The release of water from the dam is made according to some policy called the ‘release policy’. Thus, the inflow of water (input) and the policy of release are the two main features of what we call the ‘operating rules’ or ‘operating policy’. A dam is maintained and operated according to the operating rules. When a dam is constructed a storage reservoir is formed automatically. Efficient operation of a dam requires meeting the demand of water from the dam properly. And to meet the demand properly, the dam should be of that size that can contain as much water to supply. For efficient operation of a dam, researchers have been studying for long. They related the storage of a dam to the inventory problem since the basic feature of a dam is storing water until it is released. But it was Professor P.A.P. Moran who for the first time gave the probabilistic formulation of a storage model for the dam in 1954 and called the theory a “Probability theory of Dams”. In a dam situation water arrives into the dam continuously which is random. Water is released from the dam according to certain policy which is usually deterministic. The random input in the dam process makes the storage function
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Definition given by Federal Emergency Management Agency (FEMA), www.fema.gov