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00072! Table 4.-HYPolhetical treatments and percentage of areas necessary 10 Increase waler Yield in the Upper Basin by 500,000 acre-feel per year Millions Percent Method of Averagel Increased of acres treated treatment increase yield (inches) (acre-feet) Alpine 1.3 5 Snow fences al 3.50 19,000 2,000 1eet aver- age spacing Subalpine 6.8 22 Maintain V3 area 2.00 249,000 In small patch cuts Aspen 3.2 20 BO-year rotation 0.33 18,000 clearculs With regeneration 20 25-year rotalion 1.00 53.000 c1earcuts with regeneration Ponderosa pine 1.5 20 Reduce to and .55 14.000 maintain 60-80 ft2 basal area per acre by patch cuts. strip cuts, thinning Mountain brush 3.3 20 Type converSIon 2.00 110.000 to grass BIg sagebrusn 17.6 5 Type conversion .50 37.000 to grass com- bined with snow fences Tolal 500.000 'Arithmetic average of adJusted or potential increases shown In table " except the aspen, which is explained in the section on aspen. Table 5.-Hypothetical treatments and percentage of areas necessary to increase waler yield In the Lower Basin by 250,000 acre-feet Millions Percent Method of Average' Increased of acres treated treatment increase yield -~-- (inches) (acre-feet) Mountain grasslands 01 10 Snow lences at 1.75 1,500 2,000 feet aver- age spacing Mixed conifer .4 33 Maintain h area 150 16.000 in small patch cufs Aspen .1 20 aD-year rolalion 0.33 500 clearcuts with regeneration 20 25.year rotation 1.00 1.500 clearcuts with regeneration Ponderosa pine 6.0 33 Reduce to and 55 91.000 maintain 60-80 It] basal area per acre by patch cuts. strip cuts, fhinnlng Chaparral 3.5 20 Type conversion 240 140.000 10 grass Total 251.000 IArithmetlc a.verage of adjusted or potential Increases Shown in table 2, except the aspen and chaparral. which are explained the sections on aspen and chaparral 24