estimation of root-zone salinity using saltmod in the irrigated area of kalaât el andalous (tunisia)

in tunisia, kalâat el andalous irrigated district is one of the most affected areas by salinization. the objective of this study was to predict the root zone salinity (over 10 years) in this area using the saltmod simulation model for subsurface drainage system. saltmod is based on water balance, salt balance model, and seasonal agronomic aspects. in the pilot area, irrigated vegetables crops such as tomato (lycopersicum esculentum), melon (cucumis mela) andsquash (cucurbuta maxima) occupy the field during summer and rainfed wheat during winter. the model predicted more or less similar values of electrical conductivity in the root zone. highest value of electrical conductivity reached during the irrigation season was 7.7 ds m-1. following the fall rains, there was a decrease of the soil salinity when the average minimum value of electrical conductivity was 3.1 ds m-1. the simulation also showed that decreasing the depth of the drain did not change significantly the root zone salinity. the depth of the drain could be reduced to 1.6 m without any damage to crops. there was a slight reduction in drainage flow when the depth of the drain changed from 1.8 m to 1.2 m. decrease of the drain depth decreased water table level. there was no variation in root zone salinities due to change in drain spacing. the predicted drainage flows were related to the occurrence of irrigation and rainfall. in this study, calibration of saltmod for water-salt balance parameters proved the validity of the model for the local conditions.