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<br />"A:<'''UM POOL <br /> <br /> <br /> <br />- <br /> <br />\ <br /> <br />~/" <br />/" <br />/" <br />/" <br />/" <br />- <br />~ <br />/" <br /> <br />- <br /> <br />NORMAL <br />OPE~HIN(O <br />POOL <br /> <br />- <br /> <br />drainage areaa. The res~rvotrs are Orten conQected by ~anal.. The <br />da,,"" typLcallyhave a nor"",loperatingpool'"veral feet below the <br />emba..:.;"",..t top. Irrigation reser"oir.s maIntain thh ?ool during the <br />late spring and earLy s.'mmer. The W"~er lev~ 1 is ',"ually 10'"'''1' Juri'lg <br />th" fall and '~Inter. So::.e reservoirs ""'y be dry in "b~~r. Th.. aor"",l <br />operating pool is the pM1 that could be e"l'"cted during the flood <br />Season. Th~ 9toragc 3vailable to handle an in~o~tng flood without <br />o"ertopping, as.howni'lftgure1, is thevolu""'bct"eenthe nor!l1al <br />pool and the maximuM pool or top of th~ da~. <br /> <br />- <br /> <br />- <br /> <br />~ <br />/" <br />~ <br />~ <br />~ <br />/" <br />~ <br />TOP orOA.. // <br />OUTLET\IIORIIS --::-- <br /> <br />Q <br />"- <br />> <br />'" <br />~ <br />'< <br />\ <br /> <br />The outlet "orks, .ometiOle$ called ~h~ ~aervic" spillwIlY", h <br />usually Il concrete conduit with a s"",llin~llke SHucture and a gat" <br />with its controls loca~ed on the top of :he d"'m. It is used to drain <br />the reservoir or release hrigation water. Most of the tnsp~cted ds",s <br />have an emerg~ncy spillway; the sr11l~ay 1s usually sn earth-cut <br />channel through ~he natural ground to allow excessive flood inflow to <br />hypaas the e",bankm"nt without OVertOpping. So..." da",s, howover, ...ere <br />built wlthout ,~pUlways. <br /> <br />- <br />- <br /> <br />TOP or OAM <br /> <br />Pro", the stsndpoint of dam safety, the hydrologic design of a cia", <br />alma dt avoiding oVertopping. Overtopping is espeetaily dangerous for <br />an earth da" becnuu ~he downrush of wa~ers over ~he crest "MY l,r~a~l, <br />thedallle",ban;:lIlent. <br /> <br />MAXIMUM POOL <br /> <br /> <br />EMERGErKv SPILLWAY <br /> <br />';TOP"GEAYAiL"IU.E FOR <br />FLOOO iNFLOW <br /> <br />(iRRIGATION OR WATER <br />SUPPLV STORAGE <br /> <br />__OUTLET WORK$ <br /> <br />The Cor~s of Engineer. design" its dams to aafety pnss t~e e8:i- <br />_tad PrObable :iaxbnulIl Flood that COuld be generated in ~he basin <br />upanea", fro," the du.. The Probablo ~aximu~ flOOd (P~) is ~he flood <br />that _y bee"Pected froOlthe ",ost severe combination of eritical <br />:::ctccrol".;~e dO'; hyJre>lvgic cu,,,ii<.ions thao "re reasonabLy p<lss tbLe t~ <br />the region. This 16 ge'lerally ~he sccepted criterion for ""'jor ddms <br />throughout the world and is the stanJard fordam.afety where Over- <br />topplng would po.e any threat to hUlIlan ll~". The PM? 1. derlveJ by <br />using p,.cbnble ""Xi"'ll" ?nclpito~ton bfnr"",tjon ~hat J.~ ,;ener,.:ly <br />available frol1 the li"tlon;ll weHner Service. <br /> <br />NORMAL Of>ERATING <br /> <br />--------- <br /> <br />-- <br /> <br />DOWNSTREAM <br /> <br />. <br /> <br />'" <br />.~ <br /> <br />TYPICAL DAM <br />FUNCTION AND OPERATION <br /> <br />.. <br /> <br />VCllIJt.AF I <br /> <br />FiGURl; 1 <br />