WSP11706

• File Number: 8271.300
• Description: Colorado River Basin Salinity Control Program - General Information and Publications-Reports
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1980
• Title: Development of Procedures to Evaluate Salinity Management Strategies in Irrigation Return Flows
• Water Supply Pro - Doc Type: Report/Study

Table 3.3. Characteristic analysis of soil-water system models.

G~t&

Reference

Oster, J. D.
and J. D,
Rhoades, 1975

'"
'"

Oster, J. D.
and B. L.
McNeal, 1971

Constituents
n:odeled
ea2+, Mg2+,

+ 2-
Na , S04 '

Hoo;, SAR,

EG

Individual
ions, and
EG,

Major Assunptions

Soil profile in steady state
with irrigation water.

pH of the solution was assumed
to be governed by soil carlxm-
ate equilibria.

Soil lime (CaCXl3) was assumed
present in sufficient quantity
to saturate the soil solution.

Drainage waters were assumed to
be in equilibrim. with 0.13 atm
of OJZ' the average partial
pressure detennined at the 80-
em depth in 1 ysimeter studies.

Equilibriun concepts with
respect to concentrations of
constituent ions.

Each micro equivalent of QH-
generated or consured in a
reaction for each unit of
GEe (meq/1OO l!JIl), muld
change the soil pH, in the
pH range studied, by O. 01
pH unit.

Input data Results
Requiremmts _.__ _ _ __._

Ionic composition (1) Adequacy of the computer n:odel
of irrigation for predicting the drainage water
water, and drain- COIll!X'sition was daronstraJ;ed by the
age water, leach- EG, total salt burden, sot- and SAR.

ing fr~ttion, _ (Z) Correlations between measured
appropna e e<jlll. - d cal ilia ed . f
lib . tants an c t concentrat~ons 0
H ~ ~ .thin ea2+, ~+, and H003 were less
Pthe' il Zf"\011 satisfactory.
so pro ~ e. 2+
(3) Measured Ca ion concentrations
tended to be greater than calculated
values, whereas reverse was the case
with MgZ+

(4) Both salt precipitation and
mineral dissolution significantly
affect the EG of the drainage water,
with relative DBgnitudes varying
with the irrigation water.

(5) The extent of salt pickup or loss
was dependent upon COOlpOsition of the
irrigation VJater, leaching fraction,
and the partial pressure of OJZ'

M:xlel 1, Used Debye-Hiickel equation
and considered precipitation, of
salts, CE, soil pH buffer capacity,
ionic activities, 504, Heo] and 003
pairs of ea, Na, Mg, and partial
pressure of 002.

M:xlel Z, Sane as above, except ex-
tended Debye-Hiickel equation was
used,

Canposition of
soil":saturation
extract data, GEe
of soil, percent
of water at satur-
ation and at field
water content, and
the estimated
partial pressure
of OJZ'

M:xlel 3,
CaS04,-

Included only ion pair of

M:xlel
Applications

Study conducted
with 1 ysimeters
filled with
Pachappa soil
and irrigated
with eight
typical westem
U. S. waters.

Data from
Southwest Irri-
gation field
station at
Brawley,
California

.