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,,';. Matrix n.".;,...22lli: ~ .~'...." ~' --'-'-- - Page 8 July 24,2000 ~5 Mmix~~.. ~-...........- -- Page 9 July 24, 2000 tn u.. c..l C '001 ~ OIl CoO '- I'll ..c '-l ~ -001 Cl tn u.. c..l C '001 ~ OIl CoO '- I'll ..c '-l ~ .001 Cl 0.0 250.0 500.0 750.0 1912 18000 17000 16000 15000 14000 13000 12000 11000 10000 9000 8000 7000 6000 5000 4000 3000 2000 1000 0.0 1933 , 1 1922 ... IT 1932 1942 ; 1952 1962 i 1 1972 ~ 1982 II 1992 ..-. Releases were increased throughout June to delay the filling of the Reservoir beyond the customary date of July 1 to avoid a spill of the reservoir caused by continuing precipitation on an unusually late occurring snowpack. The peak average daily inflow of 1,796 cfs occurred on June 17, 1995. The Reservoir filled to the crest of the spillway on July 11, 1995. Outlet works releases were reduced, forcing [the water level to rise above the overflow spillway], and the flow below the Reservoir was maintained below the maximum safe channel capacity. The maximum average daily release of 933 cfs was made July 13, 1995, and the maximum storage of 103,927 acre-feet occurred on July 14, 1995. Releases were then reduced until they were below the recommended maximum fishery flow [250 cfs] by the middle of August. _."W ... ..'-"'", ---"-~-'l i _.W' ..............!. I' According to the Annual Operation Plans of the Fryingpan Arkansas Project for the Water Year 1995- 1996, the following describes the operation of Ruedi Reservoir during the 1995 flooding event: --- J.__ "-1 ..- -.- r-- I. .....1 J. , ........... .. 1 ~ ' =T=_~-::'=-~=!::"-===~--1!9183 __!_~~~9 ".now _ ww. ; _w___ : _w-:_~..__ ............ : ...... ' ....................... ~ 3.2 Ruedi Reservoir 0 The U.S. Army Corps of Engineers hydrology for the Roaring Fork River is based upon the assumption that Ruedi Reservoir will act as a flood control reservoir for major runoff events, including the one in 500-year event. Ruedi Reservoir was not constructed as a flood control reservoir, but provides residual storage that can capture flood events based upon normal operation. It is conceivable that the sto~age volume reserved in the spring for filling would not be adequate to contain a prolonged flood event, and the emergency spillway would release water uncontrolled. This situation began to occur during the spring runoff in 1995, although the discharge on the Fryingpan River was maintained below the maximum safe channel capacity. erations durin 1995 . I .. ... ....................... ........... ............... ........... ..... ..... ...... .......... I..... ........ ........... I....... . ,...... ..... ......... ......... .......... ....... ......... .. ......... ........... ......... . ......... I......... .......... I.... ~~... 'L ""-u. "" ....... 'fo.J I,p..J ~ l.. w.-J ll. . , . , 192J 1938 1957 Roaring Fork River A~ Glenwood Springs. S~aLion Nunber: 09085000 1953 1943 Figure 4 1948 Co. 1958 1963 Permanently assigned flood control storage in Ruedi Reservoir could not be economically justified at the time of construction. However, annual storage of snowmelt runoff indirectly provides the objective of flood control and can appreciably reduce the downstream flood menace in the Fryingpan, Roaring Fork and Colorado Rivers. If the reservoir is operated carefully for flood control by evacuation of storage prior to forecasted heavy inflow, complete control of most snowmelt floods in the reservoir can be attained. There is still a possibility of rare extreme floods that exceed the capacity of Ruedi Reservoir to control them. With the exception of these extreme events, the operation of Ruedi Reservoir reduces and stabilizes flows downstream from the dam. By providing more uniform flows, fish habitat can be established to provide better fishing conditions in early months of the fishing season. Ruedi Reservoir has a total capacity of 102,373 acre-feet at the spillway and provides replacement for out-of-priority depletions to the Colorado River by the Fryingpan Arkansas Project, as well as for West Slope agricultural, municipal, and industrial uses on a contractual basis. The reservoir operated for recreation, wildlife habitat, and indirectly for flood control. water water is also 1000 1250 The dam was designed for an inflow design flood of 17,500 cfs at a IS-day volume of 100,000 acre-feet. The probable maximum discharge is 5,540 cfs from the spillway and 1,810 cfs from the outlet structure. The total probable maximum discharge from the outlet structure and spillway is 7,350 cfs, approximating the 500-year flood in the Town of Basalt. 1500 1750 The only substantial structure that affects the flow in the Roaring Fork River is the Ruedi Dam, located on the Fryingpan River approximately 17 miles east of Basalt. The Ruedi Dam is part of the Fryingpan- Arkansas Project to divert water from the Colorado River basin to the Arkansas River basin. Ruedi Reservoir was constructed by the U.S. Bureau of Reclamation and made operational May 1968 2000 Figure 3 Roaring Fork River A~ Aspen. S~a~ion Nunber: 09073500 ort Town of Basalt, Co. Ea le & Pitkin Counties, Colorado 4.4 Flood Protection Measures ort Town 0 le & Pitkin Counties, Colorado