Assessing the effect of an interceptor drain in controlling soil salinization expansion using HYDRUS-2D

Abstract

Groundwater overexploitation where fresh and saline aquifers are adjacent to each other increases saline water hydraulic gradient, and salinity moves toward fresh aquifer which intensifies salinity in shallow aquifers. In Qazvin plain located in the northwest of Iran, salinity is expanding under this mechanism. The purpose of this study is to assess the effect of constructing an interceptor drain as a structural solution in controlling salinity expansion. By means of HYDRUS-2D, the presence and absence of drain were simulated in 5-, 10-, 15-, and 20-year periods. Results have shown that in different distances and depths, interceptor drain can control salinity both in short and long terms. Twenty years after the construction, primary salinity in presence of the drain has increased by 59.5% and 89.5% at 50 m and 150 m on the left side respectively due to solute movement toward the drain, while in the absence of the drain, salinity has increased by 250.5% and 275.2% in the same place due to inverse gradient. At 50 m and 150 m on the right side of the drain, primary salinity has increased by 43.8% and 51.9% and 55% and 173.3% in the presence and absence of the drain, respectively. Also, in drain’s presence, primary salinity has decreased by 16.1%, 15.2%, and 13.8% at 3 m, 5 m, and 7 m respectively while in drain’s absence, salinity has increased by 203.2%, 197.1%, and 133.8% at the same depths, respectively. Thus, interceptor drain is an effective solution for controlling salinity in areas under the same conditions. Also, as the distance from drain increases, its effect decreases.