RECLAMATION OF SALINE SOILS ADJACENT TO REHABILITATED IRRIGATION CANALS

A 3-yr study was conducted at eight locations in southern Alberta to monitor changes in soil salinity and groundwater conditions adjacent to rehabilitated irrigation canals. Monitoring activities included: measurement of water-table depths, soil moisture content and irrigation or precipitation amounts; and annual soil sampling and analysis to evaluate changes in soil salinity and sodicity. Soils were classified as to their present suitability for irrigation according to current land classification standards. A general decrease in the level of the water table was observed in only about half of the affected areas. Improvement in the salt-status of some soils was detected when water-table levels were maintained at depths greater than 1-1.5 m throughout most of the growing season. Irrigation and major precipitation events promoted some leaching of excess salt below the upper portion of the root zone. However, only two of the land units improved sufficiently to permit reclassification into an irrigable category. Major precipitation events, combined with irrigation events, contributed to the persistence of shallow groundwater levels at several plot locations because soils were nearly saturated to the ground surface. Additional surface or subsurface drainage will likely be required within most of the land units investigated, to permit adequate control of the water table and leaching of soil salts within a reasonable time frame.