Assessing soil salinity hazard in cultivated areas using MODFLOW model and GIS tools: A case study from the Jezre’el Valley, Israel

A high water table and soil salinization processes are common in irrigated fields in the Jezre’el Valley of Israel. This valley, located in the Lower Galilee in the northern part of the country, covers nearly 300km2. In general, salinization is accelerated when a field is underlain by a shallow, semi-confined aquifer exerting upward hydraulic pressure, which impedes drainage of the overlying soil layers. Owing to its hydrological setting, the Jezre’el Valley has inherent drainage problems, which were aggravated in the 1960s by the introduction of intensive irrigated farming. The water table rose, leading to soil salinization problems. By 1989, 1500ha showed soil salinity problems and by 1991, an area of 3300ha was affected by salinity. In this study, the MODFLOW groundwater flow model was used to simulate groundwater levels in the Jezre’el Valley. Geo-database and ArcGIS techniques were used for model input of the required dates, spatial analysis of the model results, and assessment of areas under soil salinity hazard, based on two hydrogeological criteria: (1) groundwater table depth from the soil surface and (2) difference between groundwater levels in the upper soil layer and semi-confined aquifer. It was found that the total area with intensive soil salinization is 325ha, and that with potential soil salinization 6275ha. With the appropriate input, a spatially distributed groundwater flow model such as MODFLOW can provide reliable information for the planning of an effective subsurface drainage system to prevent soil salinization.