WSP00415

• File Number: 8103
• Description: Arkansas river Basin Legislation
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 1/31/1968
• Author: W W Wheeler and Asso
• Title: Coordinator of Natural Resources - State of Colorado - Exhibits on Water Legislation Investigations for the Arkansas River Basin - Volume IV --January 31 1968
• Water Supply Pro - Doc Type: Report/Study

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caused by evaporation of the neutral salts of sodium chloride and

sodium sulfate. Alkaline soils are characterized by black alkal I

deposits or "slick spots" and contain either sodium hydroxide, sodium

carbonate, sodium bicarbonate, or large proportions of exchangeable

sodium, in addition to any neutral salts. The term "black alkal i"

is derived from the fact that with high alkalinity organic matter

is dissolved and deposits on the soil surface as a dark brown or

black stain. The water users of the Arkansas Valley are quite

fortunate in having a water supply that is primarily saline in

character, rather than alkaline. A saline soil is generally loose

and friable which permits percolation and the leaching of salts

appl led in the irrigation waterj whereas, an alkaline soil has none

of these desirable properties.

The principal effect of a highly sal ine soil is that it

increases the osmotic pressure in the soil solution. Osmosis is

the process by which a fluid passes through a semi-permeable membrane

such as the wall of a living cell into a solution of higher concen-

tration. A high concentration of salts in the soil solution reduces

the differential concentration in the soil and plant solutions which

results In a lesser movement of water from the soil to the plant.

The effects of salt' can be compared to the effect of a lack of moisture

on a normally fertile irrigated soil. The wilting point for this

type soil will generally vary from 1.3 to 1.8 atmospheres. Some of the

irrigation water presently used in the lower part of the Arkansas

Valley has salt concentrations in excess of 2 atmospheres. At the

root zones, concentrations may be much higher. The plant literally

starves Itself for water due to its inability to utilize it, even

though it has an adequate supply physically available. (See Exhibit J

for a comparison of yields under various salt concentrations).

In order to minimize the effect of high salt concentrations

in Irrigation water, it is necessary to over-apply In order to leach

salt concentrations beyond the root zone. If high Irrigation effi-

ciencies are practiced, the salts in the Irrigation water will

ultimately precipitate within the root zone. During the 1964 irrigation

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