A survey of soil salinity and groundwater level control systems in irrigated fields in the Jezre'el Valley, Israel

The Jezre'el Valley, Israel has inherent drainage problems; high water tables are common. Intensive irrigation has led to the development of salinity problems. A number of drainage system designs were installed in the same field to manage the prevailing causes of the salinity hazards. The shallow drainage system was designed to prevent damage to the winter crops and especially to enable early seeding of summer crops. The deep drainage system was designed to maintain a relatively low water table, thereby avoiding concentration of salts in the root zone. The combined drainage system with relief wells was designed to relief upward hydraulic pressure exerted by the semi-confined shallow aquifer. To study the mechanisms of salinization and the nature of the water table regime, soil salinity and water table monitoring systems were installed perpendicular to the parallel subsurface drains. The water table monitoring systems consisted of batteries of piezometers installed at different depths and located between the drainage lines. The most efficient method of drainage was found to be a combination of shallow and deep drains with relief wells wherever the semi-confined shallow aquifer was present. A noticeable improvement of the soil salinity, to below 4 dS/m, was observed 2-3 years after the drainage system was installed. It was found that the water table should be more than 1 m below the soil surface, in the spring season, to prevent soil salinization.