Effect of shallow groundwater table on crop water requirements and crop yields
In areas with shallow water table (generally less than 3 m), some crops can draw water from the groundwater, crop yields can often be enhanced and the amount of irrigation applied can be reduced significantly. Under very shallow water-table conditions (0.5 m depth), wheat extracted almost all its required water from the groundwater whereas sunflower extracted more than 80% of its requirement. It was concluded that 1.5–2.0 m was the optimum water-table depth for all the crops studied. The present system of allocation of irrigation supplies, especially in the areas where water table is shallow, needs modification to avoid inefficient use of water. When the water table is less than 2 m below the soil surface, most crops can obtain a substantial portion of their needed water from the groundwater and consequently irrigation rates can be reduced below the evapotranspiration rates.