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<br />000723
<br />
<br />toward land may even exceed) previous esthelic
<br />levels (Daniel and Boster 1976). Further, some
<br />forest types, such as aspen, may best be re-
<br />generated by clearculling, or some other form of
<br />stand reduction, that will promote development of
<br />vigorous new stands.
<br />Although streamflow has been shown to in-
<br />crease as a result of treatment on numerous small
<br />experimental watersheds, there is no assurance
<br />that the waler yield increases projected here can be
<br />physically demonstrated <.11 downstream reservoirs
<br />or points of use even if transmission losses are
<br />negligible, since the increased flows Olav not be
<br />detectable by conventional measu~ement
<br />techniques after combining with tluws from other
<br />sources (Bethlahmy 1974). The amount of water
<br />yield increase resulting from treatment must be
<br />taken on faith unless special gaging and statistical
<br />controls are implemented to verify the increases.
<br />Pilot demonstrations on watersheds of several
<br />thousand acres would help to verify the increases.
<br />and bridge the gap belween the small experimental
<br />watershed and large-scale water yield improve-
<br />ment projects.
<br />\'\Ieather modification to increase winter snow-
<br />pack is also being considered as a means of aug-
<br />menting the flow of Ihe Colorado River. Atmos-
<br />pheric scientists in vol ved in weather mod ificalion
<br />generally agree that snowfall can be increased in
<br />mountainous regions by 5% to 30%. with 10% an
<br />average prediction based on current technology.1()
<br />The combined effects of weather modification and
<br />vegetation modification on the same area produce
<br />a synergistic interaction that increases streamflow
<br />more than if the (\\'0 practices are applied sepa-
<br />rately. In essence. vegetation treatments become
<br />more p,fficient as precipitation increases. Assum-
<br />ing a 10% increase in winter precipitation from
<br />weather motlification, the increased efficiency of
<br />vegetation management is expected to be in the
<br />range of 5% to lOI.~h. Thus, there is justification for
<br />combining the practir.es. when po.ssible.
<br />
<br />Literature Cited
<br />
<br />Alexander, Robert R 1974. Silviculture of subal-
<br />pine furests in the central and suuthern Rocky
<br />1\10untains: The status of ollr knowledge. USDA
<br />For. Serv. Res. Pap. RM-121, 88 p. Rocky Mt. For.
<br />and Range Exp. Sln.. Fort Collins. Colo.
<br />
<br />10PSIAC Water Management Subcommittee. Herbert B. Os-
<br />born. chairman of task force report. "State-of-the-art In weather
<br />modification in the PaCIfic Southwest." April 1977 10 p.
<br />
<br />Baker, Malchus B.. Ir., and Harry E. Brown. 1974.
<br />Multiple use evaluations on ponderas" pine
<br />forest land. p. 18-25./n 18th Annu. Ariz. Water-
<br />shed Symp. [Phoenix. Ariz., Sept. 1974J, Pruc.
<br />Ariz. Water Comm. Rep. 6,60 p., Phoenix, Ariz.
<br />Barr, lames L., and David E. Pingry. 1977. The
<br />Central Arizona Project: An inquiry into poten-
<br />tial impacts. Arizona Review, Call. of Bus. and
<br />Public Admin.. Univ. of Ariz., Tucson
<br />26(4):1-49.
<br />Bethlahmy. Nedavia. 1974. Water supply as af-
<br />fected by micro- and macro-watershed manage-
<br />ment decisions on forest lands. Northwest Sci.
<br />48:1-8.
<br />Brawn. Harry E., Malchus B. Baker. Jr.. James J.
<br />Rogers, Warren P. Clary. I. L. Kovner, Frederic
<br />Larson. Charles C. Avery, and Ralph E.
<br />Campbell. 1974, Opportunities for increasing
<br />water yields and other multiple use values on
<br />ponderasa pine forest lands. USDA For. Serv.
<br />Res. Pap. RM-129, 36 p. Rockv Mt. For. and
<br />Range Exp. Sin., Forl Collins, Colo.
<br />Brown, Thomas C. Paul F. O'Connell, and Alden
<br />R. Hibbert. 1974. Chaparral conversion potential
<br />in Arizona. Part II: An economic analvsis. USDA
<br />For. Serv. Res. Pap. RM-127. 2B p. Rocky Mt. For.
<br />and Range Exp. Stn., Fori Collins, Colo.
<br />Clary, Warren P.. Malchus B. Baker, Jr.. Paul F.
<br />O'Connell. Thomas N. Johnsen, Jr.. and Ralph E.
<br />Campbell. 1974. Effecls of pinyon-juniper re-
<br />moval on natural resource products and uses in
<br />Arizona. USDA For. Serv. Res. Pap. RM-12B. 28
<br />p. Rocky Mt. For. and Range Exp. Stn.. Fort Col-
<br />lins, Colo.
<br />
<br />Daniel, Terry C, and Ron S. Boster. 1976. Measur-
<br />ing landscape esthelics: The scenic beauty esti-
<br />mation method. USDA For. Serv. Res. Pap. RM-
<br />167. 6r. p. Rocky Mt. For. and Range Exp. Sln.,
<br />Fort Collins, Colo.
<br />
<br />DeByle. Norbert V. 1975. The aspen forest afler
<br />harvest. p. 35-40./n Uti! ization and marketing as
<br />lools for aspen management in Ihe Rocky
<br />Mountains: Proceedings of thesymposium.lFo~t
<br />Collins. Cola.. Sept. 8-9. 1976J USDA For. Serv.
<br />Gen. Tech. Rep. RM-29, 120 p. Rocky Mt. For.
<br />and Range Exp. Stn., Fort Call ins, Colo.
<br />
<br />Ffol1iolt. Peler F., and David B. Thorud. 1974. Veg-
<br />etation management for increaseu waler yield in
<br />Arizona. Tech. Bull. 215, Agric. Exp. Stn-.. Univ.
<br />Ariz.. Tucsoll. 38 p.
<br />
<br />Franzreb, Kalhleen E. t977. Bird population
<br />changes after timber harvesting of a mixed co-
<br />nifer forest in Arizona. USDA For. Serv. Res.
<br />Pap. RM-184. 25 p. Rocky Mt. For. and Range
<br />Exp. Sin.. Fort Collins, Colo.
<br />
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