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3) South Boulder Diversion Canal <br />Denver Water diverts as much native and transbasin water as it can through the South Boulder <br />Diversion Canal during the winter, attempting to fill Ralston Reservoir by December 15. If <br />Ralston Reservoir fills by December 15, then the South Boulder Diversion Canal is typically shut <br />down until March 15. The South Boulder Diversion Canal is otherwise used to supply water to <br />the demands placed on the Northern system. <br />4) Ralston Reservoir and Moffat Treatment Plant <br />Ralston Reservoir is used in conjunction with Long Lakes to supply water for regulation at the <br />Moffat treatment plant and to serve Denver Water's raw water contract deliveries. Ralston <br />Reservoir stores diversions conveyed through the South Boulder Diversion Conduit and native <br />and transbasin rights from South Boulder Creek. The City of Arvada's raw water supply comes <br />primarily from Ralston Reservoir through contract with Denver Water. Ralston Reservoir is <br />typically operated to not drop below 3,500 ac-ft because increased manganese levels below this <br />level interfere with Arvada's water treatment processes. <br />Denver Water may release from Ralston Reservoir in exchange for water diverted out-of-priority <br />at Antero, Cheesman, or Eleven Mile Reservoirs, or any upstream diversion points on the South <br />Platte River. Exchange releases are made to either Ralston Creek or Clear Creek via the Ralston- <br />Clear Creek Canal. <br />Southern System <br />S) Roberts Tunnel <br />The tunnel is typically operated at a minimum of 60 cfs to allow for operation of the Roberts <br />Tunnel Power Plant that was constructed at the east portal of the tunnel in 1988. Maximum <br />deliveries through the tunnel are managed to keep North Fork South Platte River flows below <br />680 cfs at the Grant stream gage (ID PLAGRACO) and 980 cfs above the confluence with the <br />South Platte River main stem. <br />6) Antero Reservoir <br />Antero Reservoir provides long-term storage reserve to carry the Denver Water system through <br />long drought periods. The reservoir is generally operated near capacity because the reservoir is <br />difficult to fill with its relatively junior water rights. Operations with Antero Reservoir will <br />typically keep water in the reservoir during the first year of a drought while moving the water <br />down to Eleven Mile Reservoir and Cheesman Reservoir starting in the second year of a drought. <br />Pursuant to the Consolidated Ditch cases agreement, Antero Reservoir is operated so that it can <br />store water to replace evaporative losses over the year. In addition, Denver Water typically <br />maintains outflows from the reservoir at 5 cfs or natural inflows, whichever is less. The rate is <br />agreed on internally and not governed by any outside agreements. <br />7) Eleven Mile Reservoir <br />Eleven Mile Reservoir is operated to provide carryover storage during drought periods. The <br />reservoir is generally operated near capacity because the reservoir is difficult to fill with its <br />Denver Water Board Operating Memorandum 36 of 40 <br />