Watersheds differ in so many respects that it is difficult to say what is an 

 "average" watershed. Yet the situation at Joes Valley Reservoir on the Manti-LaSal 

 National Forest in north central Utah t>T)ifies many of the problems the Forest Service 

 has to deal with in the present and in the future. 



The purpose of this discussion is to examine some of the economic factors (relating 

 to public needs and influences described above) that must be considered when planning 

 for watershed stabilization and rehabilitation. Although data from a portion of the 

 Joes Valley watershed will be used for purposes of discussion, this is not an after- 

 the-fact evaluation of the desirability of the Joes Valley CEmery County) Project or 

 the feasibility of stabilization and rehabilitation of that watershed. Rather, it is 

 a look at some typical factors that should be emphasized in planning similar future 

 proj ects . 



Data from the North Dragon Creek subwatershed which drains into Joes Valley Reser- 

 voir will be used to illustrate specific points about the ty-pical problems discussed. 

 The area is heavily grazed, is a heavy producer of sediment, and the data on the water- 

 shed are more complete than for any other watersheds serving the reservoir. 



IMPORTANT CONSIDERATIONS 



There is seldom doubt about the worth of establishing water projects; however, for 

 particular locations there may be great disagreement as to the propriety of this use of 

 resources. But once a project has been approved and installed, the conclusion would 

 have to be drawn that society as a whole deemed it worthwhile; certainly the provision 

 for meeting increasing water demands would seem wise. However, water storage and dis- 

 tribution facilities are not cheap, either in terms of dollars or in total resource use, 

 and there is no reason to expect the cost of such projects not to go up in the future. 



Preplanned Project Life 



A conservative cost estimate of the Joes Valley Reservoir construction and distri- 

 bution system attendant to that storage is about $7.5 million, which provided 62,500 

 acre-feet of storage capacity: 



Component Volume 



iacve-feez) 



Dead storage (sediment pool) 8,500 

 Inactive storage (conservation pool) 4,000 

 Active storage 50 ,000 



Total 62,500 



The installation of this system was approved on the basis of a 100-year expected 

 life. This life expectancy was provided by creating the 8,500 acre-feet of dead storage 

 to accommodate the sedimentation which was estimated at a rate of 85 acre-feet per year. 



This points up an element of illusion in an analysis that assumes some specified 

 life span such as 50, 100, or 120 years for a reservoir. If the sediment pool is 

 expected to fill within a specified period either due to natural erosion and sedimenta- 

 tion rate or to an accelerated rate caused by damaging use, then it must be assumed 

 that the site either will be abandoned or removal of silt will be necessary to provide 

 additional years of service. But what is the reasoning that makes abandonment more 

 acceptable than dredging? Dredging is expensive, but so is the construction of a dam; 

 therefore, if we accept the idea that water is becoming an increasingly coveted commod- 

 ity, then regardless of the investment, the stating of a life expectancy for the reser- 

 voir is open to criticism. This criticism is even more justified if alternative project 

 sites are limited or nonexistent. 



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