Effect of Enhanced Water Allowance on the Performance of Tile Drainage System at Shahbaz Ghari Pilot Project area of Swabi Scarp

Field study was conducted at Shahbaz Ghari Pilot Project Area of Swabi SCARP to evaluate the effect of enhanced water allowance on the performance of tile drainage system, from August to December, 2002. Average water table depth from 17 observation wells at site 1-A and 25 at 1-C was recorded weekly. For the determination of drainage coefficient, laterals discharge was noted from 7 laterals at site 1-A and 2 laterals at site 1-C on weekly basis. To determine EC and pH, soil samples were collected from the root-zone at head, middle and tail of the research area; water samples were collected from all laterals at both site. The cropping pattern and yield of the major crops before and after increase in water allowance were assessed through farmers interviews. Average water table depth from the ground surface at site 1-A ranged from 0.54 to 1.34 m and at 1-C it ranged from 0.75 to 1.45 m during the study period. Actual drainage coefficient at site 1-A ranged from 1.36 to 2.51 mm/day whereas at site 1-C it ranged from 0.24 to 1.09 mm/day. Average electrical conductivity of soil at site 1-A was 0.84 dS/m. EC of drainage outflow of site 1-A and 1-C was 0.93 and 0.76 dS/m, respectively. The pH values of the soil and drainage water of both sites were alkaline (8.10-8.58). There was no significant change in cropping pattern but yields of sugarcane, rice and wheat were increased by 16, 24 and 37%, respectively, after the increase in the water allowance. According to the farmers, salinity and water logging problems have significantly declined after the increase in water allowance. It can be concluded from results that after increase in water allowance the singular tile drainage system of Shahbaz Ghari Pilot Project area is working well