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<br />n0070!' <br /> <br />acres have hl'I'n classified as alpine. virtually all of <br />it in the Upper Basin. About 98% is Natiunal Fores! <br />land. The climate is cold. wel. and wind\'. Pre- <br />cipilation averages 40 inches or more annually, <br />and comes mostl\' as SilO\\", which is redistributed <br />by the wind. \Vater yield a\'eraKCs 20 to 40 inches; <br />85% is conCtmtrated in the :-.tay-July snowmelt <br />period. <br />There is potential fOf incr1!asing water yit!ld on <br />selected sites where c\'<lporalion of windblown <br />snow can be reduced by trapping snow in large <br />drifts lfig. 71. Where sno\\' trapping is efficient. <br />tests have shown thai roughly fiO 10 120 feet of <br />fence is required 10 retain an extra acre.foul of <br />water in the snow drift at the start of the mdt <br />season (~Iarlinelli 1975). In terms of volume per <br />unit length of fence, this amount is equivalent to <br />363 to 726 (:ubic feet per foot of fence or .H to 88 <br />acre.feet per mile of fellce. If fences could he <br />spaced at 500- to I.ooo-foot intervals. fur example. <br />the extra water trapped would he equivalEmt to it <br />uniform depth of about -i to 17 inches over the ama <br /> <br />b!'twcen fences. Iluw!!\'cr. increases of this mag- <br />nitude have not heen demonstrated over large <br />areas. In neld application. spadn~ of fences could <br />vary considerably depending on terrain. wind. and <br />SIlOW supply. If spacing should average 2.000 feet. <br />the potential for incwasing snow sloraRe would be <br />2.2 to -i.-i inches. Even this amollnt should he con- <br />sidered tentative until results from additional re- <br />sl!arch and pilut tests become availabll!. In addi- <br />lion, most artincial slructUff!S are easily seen from <br />long distances: therefore. the visual impact of such <br />harrims should be laken into account. <br /> <br />:\Iountain Grasslands <br /> <br />High elevation mountain grasslands (fig. 81 and <br />uther large forest openings covered by grasses. <br />forbs, and low-growing shrubs prO\'ide additionClI <br />opportunilr to increase waler yield by snow man- <br />agmnenl. These areas are beluw timberline: the <br />reason ther are treeless is nol always clear. ThBte <br /> <br /> <br />Figure 6.- The Ilploe looe In Colorado with Iflnsitioo 10 subalpine vegetation II righl. The <br />alpinllone occupies aboul1.3 millioo aCles 10 Ihe Upper BllSin and only Iboul 2,000 acres <br />io the Lower Basio. <br /> <br />7 <br />