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<br /> <br />nOunI' <br /> <br />tributaries. Of particular interest are streams thai <br />emerge from IhH mountains and flow across hot. <br />dry lowlands In reach major slrt!am~ and reser. <br />voits. Total area occupied by these billlds of n:!ge- <br />lalian exceeds IOO,UOO Heres. the estimate for the <br />Lower Basin alone. ~o acreagl~ figure is Hvailable <br />for the Upper Basin. Commun riparian trees and <br />shrubs are cOftonwood, willows. salt cedar. arrow- <br />weed. saltbushes. mesquite. s~'(;amore. and alders. <br />Elevations range from about 1,000 felll to over <br />7.500 feet. Estimates of potential e\'apOlranspira- <br />lion for the lowest elevations are as hiRh as 6 feel <br />per plat. Tnl! upstream riparian areas are of special <br />inlNest beC<luse they are (II areas of hea\'y waler <br />consumption. (2) cun\'e\,ance svstems for watN <br />yield increases gtmerated on upst-ream watersheds, <br />(J) areas of high potential for saving water by <br />f:radication of trees and shrubs, and 1.\) afHas of <br />hi~h SCl~Ilit: value and high value for wildlife and <br />recreation. <br />The potential for increasing water yiPld in the <br />upstream riparian areas can be ~n:ater per unit area <br />than for any oltwr vegetation type. \\'aler savings of <br /> <br />from [) to 2.\ inches apl.war possible wh!'n riparian <br />Vt:gt:tation is f:radicall~d alnn~ permanently flow- <br />ing streams (Horton and Campbell 197.\). IIow- <br />c\"er, extensive remo\'al of trees and shrubs from <br />these areas could impair scenic and recreation val- <br />ues. ad\'l!rsel~' affect channel stability. and destroy <br />some of the most producti\'c wildlife habitat in the <br />South\\'csl. Less lhan complete removal of trHcs <br />and shrubs would correspondingl}' reduce the <br />water sa....ings potential. Thus it appears unlikely <br />that upstream riparian areas can he counted on for <br />significant augmentation of tht: Woller supply. <br /> <br />Summar)' of Potential Inc.:reases and <br />Comparison with Earlier <br />Estimates <br /> <br />The potentials for increasing water yield in 11 <br />covertypesaresullunarized in lablps 1 and 2 for the <br />Upper and l.ower Basins, The data are presented as <br />ranges of average onsite increases in area inches <br /> <br />I <br /> <br />. <br /> <br />~..'l <br /> <br />,_:, <br /> <br />... <br /> <br />'. '.~ <br />.-, << <br />..,~ .- <br /> <br />-' <br /> <br />Figure 24.-Upstream riparian vegelllllon, primllrily IIlders IInd sycamores al5,ooo leel,II10ng <br />Tonia Creek In cent rill Arlzonll. Waler use by Ihis streamside v81ilellltion is high in summer <br />and low in winler, when this pholO WIIS laken, <br /> <br />19 <br /> <br />I <br />