Estimation of root-zone salinity using SaltMod in the irrigated area of Kalaat El Andalous (Tunisia)

摘要

The objective of this study was to predict the root zone salinity in the irrigated area of Kalaat El Andalous using the SaltMod simulation model over 10 years. En general, the model predicts more or less similar values of electrical conductivity in the root zone. Highest electrical conductivity values equal to 7.7 dS m-1 would be reached during the irrigation season. Following the rains fall particularly during the winter season there would be a decrease of the soil salinity when the average minimum value of electrical conductivity would reach 3.1 dS m-1. This seasonal variation of root zone salinity was confirmed from the measured values. Investigations were made also to study the impact of varying drain spacing and drain depth on root zone salinity and water table depth and drain discharge. The simulation show that the decrease in the depth of the drain does not change significantly the root zone salinity which reaches 6.21 dS m-1 during the irrigation season and 3.67 dS m-1 during the non irrigated season. The depth of the drain can be reduced to 1.6 m without any damage to crops. A water table depth (Dw= 1.8 m) appears to be excessive and would increase the cost of system installation. We can see a slight reduction in drainage flow when the depth of the drain goes from 1.8 m to 1.2 m. A decrease of the drain depth decreases the water table level. Although there was no variation in root zone salinities due to change in drain spacing. The predicted drainage flows have registered an evolution related to the occurrence of irrigation and rainfall. This evolution was confirmed by observed values. In this study, calibration of SaltMod for water-salt balance parameters shows the reliable validity of the model for the local conditions.