SUMMARY AND CONCLUSIONS 



A fundamental watershed hydrology model (ASPCON) has been presented which is 

 sensitive to the vegetative changes associated with grass-forb to aspen to conifer 

 succession that occurs on many subalpine watersheds in the Rocky Mountains. ASPCON 

 represents a system of hydrologic processes that are likely to result in significant 

 reductions in water yield for many western watersheds. The algorithms incorporated 

 into the model were assumed from a current understanding of these hydrologic processes 

 and a review of literature. 



When applied to an actual watershed situation, ASPCON predicts a 3.4 in net loss 

 of moisture available for streamflow when aspen dominate a former grass-forb watershed. 

 An additional 4.6 in is lost when conifers eventually replace aspen forests on the 

 watershed. The predicted reduction in streamflow between a predominantly grass-forb 

 type and an aspen type is mainly a product of greater consumptive use of water and 

 increased rooting depth of aspen. The reduction in streamflow as aspen are invaded by 

 conifers is mainly a result of different snowmelt and plant activity patterns. 



The predictive ability of ASPCON is a function of the validity of many assumed 

 relationships. Research is urgently needed to more accurately establish the hydrologic 

 changes attributable to aspen to conifer succession. ASPCON provides a framework 

 capable of incorporating new information. 



PUBLICATIONS CITED 



Anderson, H. W. 



1969. Snowpack management. In SNOW, p. 27-40. Oregon State Univ., Water Resour. 

 Inst., Seminar WR 011.69. 

 Army Corps of Engineers. 



1956. Snow hydrology summary report of the snow investigation. North Pac. Div. , 

 Portland, Oreg. 

 Army Corps of Engineers. 



1960. Runoff from snowmelt manual. EM 1110-2-1406, Portland, Oreg. 

 Bartos, D. L. 



1973. A dynamic model of aspen succession. In lUFRO Biomass Studies, p. 11-25. 

 Univ. Maine Press, Orono. 

 Blaney, H. F., and W. D. Criddle. 



1962. Determining consumptive use and irrigation water requirements. U.S. Dep. Agric. 

 Tech. Bull. 1275. 

 Brown, H. E. , and J. R. Thompson. 



1965. Summer water use by aspen, spruce, and grasslands in western Colorado. J. For. 

 63(10) :756-760. 



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