WSP07589

• File Number: 8271.300
• Description: Colorado River Basin Salinity Control Program - General Information and Publications-Reports
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1978
• Title: Salinity Management Options for the Colorado River -- Part 2 of 2 -- Page 169 - End
• Water Supply Pro - Doc Type: Report/Study

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Table 8-118. Effective value. 01 .oil .aturation
extract conductivities lor levels 01
.oJAnit1/ to be expected in the ble1lded
water 01 the Roo.eveU Irrigation Dis-
trict as the .alinit1/ 01 Centrat A....01Ia
Project UNlter increase. to 1400 mull
(based on an allDtmeot 0140, ()()() ac ft 01
Ceotrat A....01Ia Project UNlter).

TDS of
Roosevelt
Irrigation
District.
Central
Arizona
Project
Blend

1169

1200

1225

1250

1275

1300

1325

Irrigation
Number

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

Drainage Classification

Well Moderate Poor

J.J
J.J
J.J
J.J
0.0

1.2
1.2
1.2
1.2
0.0

1.3
1.3
1.3
1.3
0.1

1.4
1.4
1.4
1.4
0.1

1.4
1.4
1.4
1.4
0.2

1.5
1.5
1.5
1.5
0.2

1.6
1.6
1.6
1.6
0.3

3.2
2.3
2.0
1.4
0.7

3.3
2.4
2.1
1.5
0.8

3.4
2.5
2.2
1.6
0.9

3.6
2.6
2.3
1.7
1.0

3.7
2.7
2.4
1.7
J.J

3.8
2.8
2.5
1.8
1.2

3.9
2.9
2.6
1.9
1.3

6.1
5.2
4.9
4.3
3.6

6.3
5.4
5.1
4.5
3.8

6.5
5.6
5.3
4.7
4.0

6.7
5.8
5.4
4.8
4.1

6.8
5.9
5.6
5.0
4.3

7.0
6.1
5.7
5.1
4.4

7.2
6.3
5.9
5.2
4.6

the observed data and the corresponding fitted
damage function. In the functional notation of Y =
bernx as defined earlier, b = 0.7983, e = 2.718281828,
m = 0.6537, and x = any level of TDS within the
confines of the appropriate interval. The fitted curve
has an RZ of 0.91.

A summary of the findings for the RID is
presented in Table 3-118. Even though annual total
damages are listed as $5,409, the net contribution
from this District is considered zero due to the TDS
level of present water supplies of the RID as compared

to present and projected salinity levels of Colorado
River water in the CAP system.

SAN CARLOS PROJECT

The San Carlos Project is located in the lower
Santa Cruz River Basin, between Florence and Casa
Grande, Arizona, and includes 100,000 acres of Indian
and non-Indian land. All project facilities are operated
jointly. They include: 1) Coolridge Dam and San
Carlos Reservoir with a capacity of 948,584 ac ft at
spillway level; 2) Ashurst-Hayden Diversion Dam on
the mainstream of the Gila River 10 miles east of
Florence; 3) Picacho Reservoir with a capacity of
18,000 ac ft used to store and regulate the delivery of
water; 4) Florence-Casa Grande Canal, Pima Lateral,
and sublaterals which serve both Indian and non-
Indian lands; and 5) drainage and pumping works with
110 producing wells.

Over the last 5 years the water supply has
consisted of approximately 70 percent surface water
and 30 percent groundwater. The surface water comes
from the natural flow of the Gila River and releases
from the San Carlos Reservoir, plus the erratic flows
of the San Pedro River. The groundwater is pumped
into the system from wells scattered throughout the
project area. During the last 20 years, pumping for
both project and nonproject lands has resulted in a
progressive lowering of the water table at an average
rate of 8 feet per year to its present level of
approximately 236 feet (Babcock, 1973).

Since 1934 the project has pumped an average of
89,000 ac ft per year, but for the last 10 years the
average has been approximately 75,000 ac ft per year
(Records of the San Carlos Irrigation Project).
However, the rapidly lowering water table indicates
that this rate of pumping cannot be maintained. In
addition, yearly diversions of surface water from the
river at the Ashurst-Hayden Dam have averaged
190,000 ae ft and are a reasonable expectation for the
future.

There has been no decision on how much CAP
water the project will receive. They have requested
240,000 ac ft which would enable the district to
irrigate the entire 100,000 acres of land with a
minimum of 4.0 ac ft per acre after a110wing for losses,
which are expected to be minimized by lining a11 canals
and laterals. For the purposes of this study, it seems
reasonable to assume an allotment of no more than
150,000 ac ft to the San Carlos Project. Water sources
for the project would then bc 150,000 ac ft, Colorado
River water, 190,000 ac ft Gila River water, and
possibly 50,000 ac ft of groundwater.

The salinity of the Gila River ranges from 510
mg/l to around 1000 mg/l "mean annual" TDS (Water
Resources Data for Arizona), or an average 775 mg/l.
Salinity of the groundwater ranges from around 500
mg/l TDS for the best wells to a high of 3,957 mg/l.
Records on 64 wells are summarized in Table 3-119.
The average of these 64 wells is 1510 mg/l TDS. If we
assume 50,000 ae ft of groundwater with 1500 mg/l

193