effectiveness of collector drain on drainage coefficient(a case study: amir-kabir agriculture and industry department, khuzestan province)

abstract although lateral drains play the main role in removal of excess water from soil profile in subsurface drainage systems, but it is assumed that perforated collectors can directly remove a part of drainwater from soils. this part of discharge in subsurface drains is not usually taken into consideration in drainage design criteria, due to lack required information and its difficult estimation. if the level of collectors’ drain discharge is determined, drainage coefficient for laterals can be adjusted depending. consequently the distance between laterals is increased and economic value of drainage system design is more justified. this research was conducted in drainage network of amirkabir agro-industrial unit with the purpose of determining collectors’ discharge level and lateral’s drainage coefficient adjustment. therefore, measurement of water table, discharge of laterals and collectors in arc2-14 farm having 25 hectare size was measured. results obtained from field measurements indicate collectors directly discharge approximately 2.8 litter water per second or 2 mm per day or about 24% of total drainage discharge within the system. the actual drainage coefficient will then be reduced from 8.24 to 6.24 mm/day. this change will result an increase in lateral distance from 40 to 44 m.