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<br />how this new w~ter supply stor8ge would be op'lrated; therefore, no estimate <br /> <br /> <br />can be m8de of wh'lt the annual vClriations in the pool levels :night be. <br /> <br /> <br />d. On Dam Safety. 'l11e impact of flood storage conversion on the <br /> <br /> <br />hydrologic safety of th~ Chatfield and EX~ar Cre",k dans \;ould be insignificant. <br /> <br /> <br />Routings of the original spillway design floods resulted in freeboards within <br /> <br /> <br />ilcceptable tolerances of the mini'11um 5 feet criteria used by th.~ Corps of <br /> <br /> <br />Engineers. These routings were made asswning a starting pool eleviltion <br /> <br /> <br />resulting from one-half of the standard project rainfall flood inflow on top <br /> <br /> <br />of a full conserv8tion pool Hhich included the new \;8ter supply storage. <br /> <br /> <br />8. Conclusions. Based on historical flood experien:les in th.~ Denver area, <br /> <br /> <br />the most serious flood problems .arise froLn the intense short duration rainfall <br /> <br /> <br />floods. There is more than edequ3te storage in the Tri-Lakes system to control <br /> <br /> <br />these types of events. Operationally, the most serious problems are encoun- <br /> <br /> <br />tered Mlen mountain snowmelt releases are passed through the reservoir to join <br /> <br /> <br />uncontrolled tributary runoff in the South Platte River below Denver. L'lJple- <br /> <br /> <br />mentation of the newly developed computer model called "Denver Area Real Time <br /> <br /> <br />System (DARTS) which will be used to operate the Tri-Lakes system and make <br /> <br /> <br />short and long range runoff forecasts could help overcome some of these <br /> <br /> <br />problems. It might also help reduce some of the nuisance type flooding and <br /> <br /> <br />erosion damage associated with these events. No mAtter how sophisticated the <br /> <br /> <br />operation of this system beco:nes, it is obvious from studi,es already :nClde that <br /> <br /> <br />the downstre~n control point should not be moved below the Henderson gage. <br /> <br /> <br />Tnese studies have also demonstrated the importcmce of selecting a minmimun <br /> <br /> <br />flow of 5,000 cfs for controlling nuisance type flooding at this location. <br /> <br /> <br />Otherwise operational releases fro:n the system could be seriously hampered <br /> <br /> <br />r.esulting in a severe loss in useful ncod control storage. Recognizing this <br /> <br />J <br /> <br />. <br /> <br />. <br /> <br />. <br />