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ex./ ica i r ~ <br />• • <br />"iJATER fu`]D P,ELATRD LAND RESOURCES - <br />DOLORRS FIVER BASIN <br />COLORADO AND UTAH" <br />A Report Based on a Cooperative Study by <br />Colorado TJat?r Conservation Board and <br />1(nited Stares Department of Agriculture <br />Denver, Colorado - September, 1972 <br />Soil. Mapping Unit 3: Rock outcrop and very shallow soils of the can ons. <br />This mapping unit is along the Dolores and San Miguel Rivers and their <br />*_ributaries. Runoff is very rapid beca~lse of the steep stopes and :;hallow <br />soils r:~ith low waterholdinS capacities. Sediment yield is from less than <br />0.2 to 1.0 acre-feet per s~uar.e mile per ;ear. <br />The lzndscape is characterized by deep sandstone canyons with steep slopes <br />and long very narrow valleys, and floodol?ins. Small, gently sloping mesas <br />are zbove the canyons. Steeply sloping mesas are above the canyons, <br />Steeply sloping all(vial fans border some of the canyon walls. Numerous <br />intermittent drainageways dissect the. steep slopes. The dominant c~]ver is <br />pinyon-juniper. Oakhru.ch, serviceberry; any grass are more abl[ndan= at <br />higher elevations because of i.ncreaced precipitation. LJillo(as and I:otton- <br />wood trees oncuny small tracts along the narrow valleys. There are a few <br />irri~at?d hay fields where the valleys are wider. <br />This l±nit is composed of two maior components. About 45 percent of the <br />)snit is rock outcrop, mainly sandstone, caith some small o,Ltcrops of shale. <br />Another 49 percent of the llnir has shallow soils, less than 20 inchl~s, <br />over underlying sandstone and some shale. These soils are stony and <br />usl.Lally have loamy, light-covered surface layers. The remaining 6 percent <br />of the unit is made up of soils with dark-colored surface layers and mixed <br />alluvial soils in the Dolores and San Ptiguel River bottoms. <br />T-,.. -.--Crp•~.LC!on sod cls:nc cerlf acs o[ soil c pptc6 onia e: eS^_ Dolores Rtver Amin to Co :or sda sod U[s1 <br />. ):ma )~¢sn Fro:: i <br />fo-„nlci on. :pccCnc:poctna n[ ~sL enwd [n <br />)'ap eE ;elra cLon; preetp 4o:[oe: [eq ero[ure: pe rted <br />s; :o!: 2c rc. ,::: 1DLe Grcx Eroup, Sebprevp o: LarC i)'pC b:.aa (fca [) (fosse s) (F') (d,_s) <br />] 45 Rock and shelc ou [crops ]t.5 4,L00- T-18 43-SL IO )- ~ <br />35 I:sp lus tolls (shplLov over sondsco ne sod 9,0'10 16) <br />ahelc) <br />30 'forrloahen[s (she tlov evnr mrvls cone i <br />one shsle) <br />4 L4ch1< Ar6lm col is <br />4 Horal Es and Cryoho rolls <br />3 1'orr L[lure ncs <br />Nr(nenC :DOnL ten[ Ea[Ies[ed : <br />paten[ ^opc sedlmenc Erm ton Ms)or <br />ascerl•Ls ;(percen e): Yte!d proSlev fond <br />. (Ac. E[./ uses <br />•q. vL! : <br />SacLs[ane T]-Ill] ~O.T-1.0 1'.odcro[e shee[ rta,,e, <br />vlch s ro slCC. o aLIJ Lt (C <br />sSalC onJ 6_'lI!ef, Ja,~a 6e <br />•il~vlun L:"IS rc loCO Lly <br />