Estimation of Root-zone Salinity Using SaltMod in t he Irrigated Area of Kalaât El Andalous (Tunisia)

Abstract

In Tunisia, Kalâat El Andalous irrigated district i s one of the most affected areas by salinization. The objective of this study was to pr edict the root zone salinity (over 10 years) in this area using the SaltMod simulation mo del for subsurface drainage system. SaltMod is based on water balance, salt balance mod el, and seasonal agronomic aspects. In the pilot area, irrigated vegetables crops such as tomato ( Lycopersicum esculentum ), melon ( Cucumis mela ) and squash ( 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 v alue 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 de pth of the drain did not change significantly the root zone salinity. The de pth of the drain could be reduced to 1.6 m without any damage to crops. There was a slight r eduction in drainage flow when the depth of the drain changed from 1.8 m to 1.2 m. Dec rease of the drain depth decreased water table level. There was no variation in root z one 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. Keywords: Drain discharge, Irrigation, Salinity, Subsurface drainage, Water table.