Prepared by Muneer AhmedDepartment of Water Resources Engineering
Dam is a structure built across a STREAM,RIVER, or estuary to store water. ARESERVOIR is created upstream of the damto supply water for human consumption,IRRIGATION, or industrial use.
Dam is the central structure in a multipurpose schemeaiming at the conservation of water resources.Auxiliary works for a dam include spillways, gates, orvalves to control the discharge of surplus water, anintake structure and means for permitting boats orfishes to cross the dam.
A spillway is a section of a dam designedto pass water from the upstream side ofa dam to the downstream side.Types of spillway include:primary spillway,auxiliary spillway,emergency spillway,fuse plug spillway etc.
Significant considerations when building a daminclude: permeability of the surrounding rock or soil•earthquake faults•landslides and slope stability•water table•peak flood flow•reservoir silting•environmental impacts on river fisheries, forests•impacts on human habitations•compensation for land being flooded as well aspopulation resettlement•removal of toxic materials and buildings from theproposed reservoir area
Location- on the Karnafuli river at Kaptai in Rangamatidistrict, 65 km upstream of Chittagong.Length- 670.56mHeight- 45.7m highWidth- 45.7m (at foundation level) 7.6m(at crest level)The catchment area of the reservoir- 11,000 sq kmSince it is an earthen dam a 16-gated spillway (each 12.2mby 11.3m) with discharge capacity of 625,000 cusec has beenconstructed on the left side of the main dam.
Compared to concrete barrage and regulators rubber dams are cheaper and more flexibleand can be fully deflated during the flood season . Rubber dams can be as long as 100mand used for irrigation , small-scale hydropower generation and rural water supply.