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S ]: C l' ION II 1: Hydrology and Ilyd rau lies ^. ) Ii2'd 1'0 1,~~Z Hydrology for the Big Dry Creek was developed in accordance with the procedures outlined in the roinfaU and runoff secc-ions ] n the !lJJ)_<1 n S to rm ----1.J_r..'lJna g e_~EL!.er:.i".}"allll:l1, (He re a He r re f e ree d to os the c:r,il_ccrj.'l.....~i~nu~U. The first step in this study was to ob1.;li n rai n[ill1-- frequency elata. The isoh)'etals map" entitled "1{:,inL,ll- l1epth-!luration-l'requency Map, Denver Region," from the Crileria ~1:lllllal (hased on point rainfall dilt<l) were used to plot a groph of return period In years versus total 1'01 nfall depth in inches ["or a ]--hour, 6-hour and 24-hour roinfall. !lata from the above graph was in turn used to plot a second graph of duration 1n minutes and hours versus tota.! rainfal1 depth in inclles for IO-year, 2S-year ond .!Oo- yea r return periods. (See Plote No. Ill-l, Volume 1). No ralnfa] reduction was used for the approximatcly t\\-cn1y square mile basin sin c c from ],i g u rc IS 0 f the U. S. We a the r [)u re:w X.c'.clll1__iY~_lL_r':J pcr_.li~J......__'IO_ the factor would have he en an insigni ficallt th"O percent Thc next step in the deveIopmcnt of the ],ydro]ogy for the h;15il1 \\:JS to dctermine the iJmount of raiJ1f:J 11 that actually lwcoi1Jes runoff, ut il izing the Colorado Urb'JJl Ilydrogr;lph Procedure (ClIlll') as out J i ned 1 nth C' c: l' j t e l' i a 1<1" n U:J I . Seven key points \Vere selected along the basin channel at l\'hich the rate of runoff (in CFS) \Vi1S to he determined. The (ll'Ca In square miles of the bClsin tributary to each of the seven selected points "as II ~ ..., ,.