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<br />1564 <br />III. Summary · Hydrologic Analysis of Changes <br />in Arkansas River Flows Since 1889 <br /> <br />The hydrologic analysis of flows was divided imo <br />three time periods, ro reflecr major changes in <br />river managemenr. The firsr designared time peri- <br />od, 1889-1910, reflecrs ,he earliesr dare for which <br />continuous flow records are available. and repn:- <br />sems a fairly natural, unregulared sysrem before <br />1900. Between 1900 and 1910, the sysrem began <br />ro experience the dfecrs of limired warer importS <br />and the consrrucrion of Clear Creek, Twin Lakes, <br />and Sugarloaf Reservoirs in rhe upper basin. The <br />second designared rime period, 1910-1960. <br />refl~cts a rime period when water management <br />was fairly stable. without any major new water <br />management facilities. Transbasin diversions, <br />overall storage capacity, and active s[Qcage man- <br />agemenr increased incremenrally, bur did nor dic- <br />[ate o;tensive alterations in how the river was <br />managed. The third period, 1982-1995, rellecrs a <br />period when the Fryingpan-Arkansas Project was <br />coming on line, along with associated institution- <br />al changes in how warer was managed and a1locar- <br />ed. The 1960 ro 1982 period was nor analyzed <br />because rhe riming and magnirude of flows fluc- <br />tuated as new water storage and import systems <br />came on line. <br /> <br />The overall ner effecrs of rhe period from ] 890- <br />] 91 0 are a slighr reduction in November through <br />April flows, a reduction in spring runoff flows <br />(Mav-June), and an increase in August - <br />Seprember flows. These effects are predominancly <br />the resulr of upper basin storage pur imo service <br />afrer 1900. Mean flows for November through <br />April flows prior ro 190] are approximarely 420 <br />cfs, and mean flows for November rhrough April <br />posr-190] are approximarely 350 cfs. Mean daily <br />flow before 1901 for rhe Augusr ]-] 5 period was <br />650 cfs, while afrer 1901. the mean daily flow for <br />the Augusr ] -] 5 period was 770 cfs. <br /> <br />Flows during the 1910-1960 period were approxi- <br />marely the same as rhe 1889-19] 0 period during <br />fall, wimer, and spring. However, due ro the <br />release imported of warer rhar was srored on rhe <br />easr slope during runoff, July and Augusr flows <br />increased significancly. The mean daily How for <br />Augusr 1 - Augusr 15 for rhe 1910-1960 period <br />was approximarely 1000 cfs, compared ro no cfs <br />from 1901 ro 1910. This is an increase of 230 cfs <br />from rhe 1901-1910 period, and is almosr com- <br />pletely .[[[iburable ro trans basin imported warer. <br /> <br />Flow analysis during rhe 1982-1995 period is <br />complicared by several tacrors. Complerion of rhe <br />Fryingpan-Arkansas projecr creared tremendous <br />flexibility in rhe process of warer storage and <br />movemem. In addition. the Wettest period is on <br />record is from ]982-1987,1989-]992 is extreme- <br />ly dry, and 1995 is rhe wertesr year on record. <br />Finally, an annual flow managemenr program was <br />sraned in ] 990. This program sers rarger Row <br />ranges for ]2 months of the year, and ir involved <br />augmentarion of 1are July and early Augusr flows <br />IS some warer years. <br /> <br />Flow augmenrarion appears to continue flow levels <br />thar have been presenr since. significanr change <br />thar occurred in the early ]900's. Even rho ugh rhe <br />Row augmenracion program was operared during <br />the 1990-95 period, rhere were many days in rhe <br />Augusr 1-15 period which experienced flows of <br />less rhan 700 cfs because other facrors were ar <br />work on the river which reduced flows. The per- <br />cem of days which flows exceeded 700 cfs during <br />the ....ugusr 1 [Q Augusr ! 5 period is as follows: <br /> <br />Prior to 1910 1910-1960 1982-1989 1990-1995 <br /> <br />40% <br /> <br />75% <br /> <br />77% <br /> <br />80% <br /> <br />]1 <br />