WSP05373

• File Number: 8147
• Description: Gunnison-Arkansas Project
• State: CO
• Water Division: 4
• Date: 6/1/1948
• Author: US DoI BoR
• Title: Interim Report Gunnison-Arkansas Project Colorado Appendix H Sediment and Debris Control
• Water Supply Pro - Doc Type: Report/Study

.

Chapter IV.--Scdiment control benefit

19-4 I)
AB shwon in the previous discuseion, the potential Pueblo ~eservoir
would retain sediment amounting to 656 acre-feet per year in the Initial
Development and the Maximum Gravity Diversion. Of thie amount. 150 acre-
feet would be prevented from entering the existing John Martin Reservoir.
The remaining 506 acre-feet may be apportioned by the percentages arrived
at in Chapter II, as shown in table 9.

Table 9.--~eduction of annual sediment deposition
with potential reservoirs: Initial Development
and Maximum Gravity Diversion

Item

: Propor-
:tion of ;(Pueblo Res.)
: sediment: (ae.-ft.)
(~)

.

Sediment retained by pot en- I
~. - .t~a1~reser:voir:.-~~":""!.~~=-... .~...:...-~t. ---~~ .:-~:.

"~~-~~~~~~~;~~~K:~~~~~~:,ir~O~~~;.::~ .c~:. ~}-

-- -=- -=- _:::. -Reriia:lnd.e~~';-:=':.-=--; ~. -~--.-_~-:--_~-::: ~~... --=..:
- -:'':-- =.=- ___ ~Jd1m.l!n~=r,educ.t1:6n=ln/on: _ ~ ,i-', ,-! =-- '---
---.:IrrigatEld-=-land. " 'i"'O "0-'---. T -59'
Laterals. . .. .. ... . .. .. .. . ~ 6
Canals. . . . . . III . . . . .6
Reservoirs. . . . . . . " 26
Arkansas River. .. . . . . . t: ;

6 6 -- '
-- 5--~--~--m
-- --
-----.--- - --

--- ..
------

- '
-- ----.-
-- _...

~,-~~~~'~:~,'

---- --~---~-

- ---
-'.
-,
----
--- -

299
30
30
132
Iii

The value of reservoir capacity conserved by preventing sediment
deposition in reservoirs is obtained by determining ,the value, of net'di_
rect and indirect benefits from that fraction of the water supply deliv-
ered from the exieting reservoirs. The efficiency of private reservoirs
averages 23.5 percent. Therefore, 72,300 acre-feet of water of the '
total 307.500 acre-feet of capacity in the private valley reservoirs, if
delivered to the total 322,000 acres of land would amount to .22 acre-
foot per acre. With 1.64 acre-feet of water per acre (the ideal head-
gate supply of 3.10 acre-feet less a shortage of 1.24 acre-feet and the
.22 acre-foot) the annual equivalent net benefits, including direct and
indirect benefits, from irrigation agriculture on land to rec.tv.
supplemental water drops from $1,371,000 to a balance between total farm
coste and gross direct plus indirect benefits (see exhibit 5). The
$1,371,000 representB the annual equivalent net benefits from agricul-
ture with a supplemental Bupply of .22 acre-feet from private reservoirs
alone. If the reservoirs, operating at 23.5 percent effiCiency, furn-
ished 1 acre-foot of water, the agricultural benefits would amount to
23.5 percent of $1,371,000 divided by 72,300 acre-feet or $4.46 per
acre-foot. This fi~re should be reduced by the $.12 per acre-foot aver-
age annual operation and mainteMnce expense of private reeervoirs. The
_ ____ __, ~ual va!:..ue_ per__acr!-foot" oCthe ,rese,uo,iz._capacity_depleted_by__,_ _ ,__._

16