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<br />possible utilization of the land and water reaources in the Conejos Division
<br />of the san Luis Valley projeot can be construated at a later date. atter
<br />the agrioultural econOlllY of the area has improved to the extent neoessary
<br />to justify the need for an additional late-seaaon irrigation supply.
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<br />Flood Control
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<br />19. Historic flood damages in the Conejos area have been determined as
<br />averaging $87,300 annually for the period of reoord. By standard am acoept-
<br />ed probability methods, flood dama~es for a lOO-year period, have been
<br />determined as averaging from $84,090 to $95,760 annually. A multiple-purpose
<br />reservoir of 60,000 acre_feet capacity at the Platoro site would have reduced
<br />the historic annual average flood damages to $24,400 or, on the basis of '
<br />probability methods, to an average of ~t23,410 to '529,090 annually. Thus,
<br />the average flood damages prevented in the Conejos area, exclusive of those
<br />prevented in New Henco, is $63,400 annually. Capitalized at 3 percent in
<br />50 years, this has a capital value of ;:~1,631,300. The plan for j oint use of
<br />the Platoro Reservoir would require that. a D4nim1llll capacity pf 4,000 acre-
<br />feet of' storage space be available for control of fall rain floods on
<br />July 31 of each year.
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<br />Costs
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<br />20. The estimated presen~ay cost of a 60,000 acre-foot capacity
<br />reservoir at the Platoro site is $3,750,000. The annual operation and
<br />maintenance costs are estimated as ()8,,500.
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<br />Allocation of Costs
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<br />21. A reservoir of 40,000 acre-feet capacity at the Platoro site used
<br />only for the purpose of flood control would prOvide the maximum control of
<br />flocd flows for the least cost; a reservoir of 60,000 acre-feet capacity
<br />used wholly for irrigation purposes would provide the regulation necessary
<br />to secure 'the optimum increase in gross crop returns at the least cost.
<br />Thus, to provide these returns by the use of single-purpose reservoirs 8
<br />total Capacity of 100,000 acre-feet would be necessary. On the basis of
<br />equivalent facilities 40 percent of the total cost: of the 60,000 acre~foot
<br />multiple-purpose Platoro Reservoir, whiehwill provide equivalent flood eOI)-
<br />trol, is allocable to flood control and is non-reimbursable; 60 percent of
<br />the cost of the 60,000 acre-foot capacity reservoir, which will provide
<br />equivalent irrigation returns, is allocable to irrigation and this portion
<br />of the total cost is reimbursable. '
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<br />Annual Costs and Annual Returns
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<br />22. Sixty percent of the total cost of the 60.000 acre-foot Platoro
<br />Reservoir, $2,250,000, is to be allocated to irrigation and is reimbursable.
<br />The annual cost, one_fortieth, is $$6,250. Sixty percent of the estimated
<br />annual operation and maintenance costs, estimated at $5,100, will be paid
<br />by the \Ster users. The total annual amount payable by ths water users,
<br />including repayment of construction costs and payment of operation and
<br />maintenance costs, is, therefore, jJ6:j.,350. Forty percent of the total cost
<br />of the reservoir, (~1,500,000, is to be allocated to flood apntrol and is
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