Hydrus-1D model calibration and validation in various field conditions for simulating water flow and salts transport in a semi-arid region of Tunisia

Abstract

In semi-arid regions like Tunisia, agricultural use of saline waters raises soil salinization risk. A land-parcel was selected in the semi-arid region of Ariana for simulating water and salts dynamics in order to assess the ability of Hydrus-1D model in various field conditions and to assess the environmental risks due to the salinization process. Four water qualities were used (C1 = 1 dS m−1, C2 = 7 dS m−1, C3 = 14 dS m−1 and C4 = 21 dS m−1) to irrigate four plots with same dose. Monitoring of the soil moisture was carried out by gravimetric method and soil salinity by measuring the electrical conductivity of the saturated paste up to 80 cm in depth. The model was calibrated during 7 days and the validation was carried out during 383 days. The measured water and saline profiles are similar to the simulated profiles which demonstrate the ability of Hydrus-1D for reproducing water and salts dynamics in such conditions. The soil salinization risk is higher with the use of C3 and C4 water qualities for irrigation. The model can be a powerful tool to assess the environmental risks related to the irrigation with saline waters in semi-arid regions. Keywords: Soil, Salinization, Risk assessment, Hydrus-1D, Tunisia