Abstract
The crop water requirements of three major crops grown in the Lower Indus Basin namely wheat, cotton and sugarcane were
determined at different water-table depths and the groundwater contribution to the total water requirement was quantified.
The study was conducted in drainage type lysimeters of size 3.05 m x 3.05 m x 5.18 m constructed at the Drainage Research
Centre Tandojam, Pakistan. Three different water-table depths of 1.5, 2.25 and 2.75 m were maintained during the study. The
evapotranspiration (ET) was more at shallow water-table depths and it decreased with increase in water-table depths. The
maximum wheat yield was obtained at water-table depth of 2.25 m whereas the maximum cotton and sugarcane yields were
observed at 1.5 m depth. The groundwater contribution to wheat crop was, 19, 6 and 4%, to cotton crop, 20, 4 and 1% and to
sugarcane crop, 21, 5 and 1% at the three water-table depths, respectively. At 1.50 m depth, the water productivity of wheat
was 8-22%, cotton 27-30% and sugarcane 34-57% higher than at 2.25 and 2.75 m depths. Therefore, there is a need to
exploit the shallow water table to reduce the surface water applications and to improve the water productivity.
