WSP02976

• File Number: 8271.300
• Description: Colorado River Basin Salinity Control Program - General Information and Publications-Reports
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 12/1/1979
• Title: An Economic Evaluation of the Salinity Impacts From Energy Development - The Case of the Upper Colorado River Basin
• Water Supply Pro - Doc Type: Report/Study

sllmptive use by agricultural production, WA,.
in WRSAs is:

W
1'''
l'V
W

H
"
[=1

lfls x~ = WS
i' A

s=l, 2, . . .. 8

(14)

Crops consume only a fraction of the
water. diverted (Wn)' The water consumed by
crops and other incidental consumptive uses
divided by water diversions gives the overall
irrigation efficiency (ex). Water which is
not consumed by crops returns to the natural
stream and becomes a source of water supply
to downstream users.

(l - as)Ws _ ~.,S 0
D RF

and, therefore

s s S 0
0'. Wn - W A ""

(15)

where WKF is the return flow of the sth WRSA.

Water ~irement for energy. If gr
and hk are the amounts of water required to
produce one unit of raw material and one unit
of final output, respectively, the total
quantity of water required in the energy
production of each WRSA is

M
I: S IS
gr r
r=l

N
+ t hS QS = WS
k~l k k E

(16)

s=1, 2.

. ., 8

Water availabilities. Using the flow
balance approac~tne-total~water consumptive
us e in agr icul tur a 1 and energy produc t ions
plus the natural outflow (FS,s+l) from upper
WRSA and return flow to lower WRSA yields the
total surface water availability (Wo) of the
s th WRSA:

wS + WS + Fs,s+l
A E

8
I: FU's - W:F = w~
u=1
u>s

(17)

Institutional restrictions

The Upper Bas in water users can use
virgin flow available to them within the
1 imi ts of the share of the Upper Bas in water
allotted to them after providing the Lower
Basin commitment of 8.3 million acre-feet.
The quantity available to each state will
however vary depending on the three cases of
availabilities outlined earlier. Thus, the
summa t ion of tota 1 consump t i ve use of wa ter
in WRSAs cannot exceed the state's allotment

f. W: +
sey

E w~:;; lilY
sey

'1:::1, . . ., 3

(18)

where y represents each state. WRSA 1 is in
Wyoming, WRSAs 2, 4, 5, 6, and 7 are in
Colorado and New Mexico and WRSAs 3 and Bare
in Utah. Further. the annual flow at Lee
Ferry (FL) entering the Lower Basin must be
at least 8.3 million acre-feet.

FL> 8,300,000

(19)

Water quality

A mass balance approach is used to
account for salt outflow (5s+1) from each
WR5A and at Lee Ferry. Some salt is taken
from the river by both agricultural and
energy divers ions. Return flow adds salt to
the river. The water diverted to energy is
assumed to all be consumptively used so
that no outflow from the energy sectqr
returns to the river. The pattern of salt
movement is thus modeled as

Ss+1 = CS WS _ CS WS _ eS WS + CS WS
0000 oE RRF

or

8S+1 + eS wS + eS WS _ eS WS = cS WS
aD oE RRF 00

(20)

where C~ represents the concentration
in the stream flow of WRSA and c~
return flow concentration.

level
is the

The salinity concentration resulting
from Upper Bas in water use is calculated at
Lee Ferry, below WRSA 8 (Figure 6). Concen-
tration is the ratio of total salts to water
volume at the point of measurement

L SL
C == ,--
FL

(21)

where CL is the concentration level at
Ferry, 5L is the accumulated salt from
upper WRSAs to Lee Ferry, and FL is
volume of flow defined above.

Lee
the
the

Estimation of CL from Equation 21
involves a nonlinear relationship which
cannot be incorporated within the LP frame-
work. Th is problem, however, is overcome by
using linear approximations of the percentage
changes in salt concentration. For the
approximations, Equation 2l can be rewritten
in general functional form:

c,t(S,F)

The total differential of Cis:
_ 1.Jo at
de - as dS + aF dF

"" 1:. dS _ S 2 dF
F F

~ dC "" f . ~ dS - ~ . :2 dF

dC = dS _ dF
C S F

(22)

25