Evaluation of subsurface drainage techniques used for dryland salinity control
Helgason, Warren Douglas
Dryland soil salinity is a major problem throughout much of the northern Great Plains region. One method of controlling dryland salinity is through the use of subsurface drainage systems. However, in western Canada there is a general lack of experience in designing drainage systems. Usually those systems that are installed in semiarid dryland areas are based on experiences from more humid or irrigated areas. This study evaluates two types of subsurface drainage systems installed in adjacent, similar saline seeps located near Swift Current, Saskatchewan. The two types of drainage systems evaluated are: (1) a traditional grid drainage design, typical of humid or irrigated regions and; (2) an experimental drainage design that uses a relatively smaller amount of tubing that is precisely placed and is valve controllable, allowing for the implementation of a water management plan. The two systems were evaluated based on their ability to control water tables, lower soil salinity, and provide the highest water quality possible so that the environmental impacts associated with re-using or discharging that water are minimized. Climatic, hydrologic, geologic and chemical data were used to characterize each saline parcel and then monitor hydrologic changes caused by the drainage systems. From the results presented in this study, there was evidence that, with modifications to the water management plan, the experimental system would be equally effective at lowering water tables as the traditional system. The study was inconclusive as to which drainage technology had the better ability to reduce soil salinity above the drain lines. Also, the salinity of the experimental drainage system effluent was observed to be much lower than that of the traditional system. Overall, both systems performed as they were designed indicating that both technologies can be successfully used in a dryland situation. However, in consideration of the reduced cost and installation effort and the more flexible operation options of the experimental system, the experimental design concept is perhaps better suited to modern agriculture on the semiarid prairies. Recommendations for use of this technology include adaptations to the water management plan that would further minimize salinization hazards.