This study was conducted during 2001-04 in which four subsurface drainage projects viz; Mardan SCARP Project (MSP), Fourth Drainage Project, Faisalabad (FDP), Chashma Command Area Development Project (CCADP) and Mirpurkhas Tile Drainage Project (MTDP) were assessed for their impact on crop yield in irrigated areas of Pakistan. Quantitative comparison made on the change in pre- and post-project conditions revealed that crop yield significantly improved due to project implementation at all sites. The yield increased from 13 to 94% for most crops. The exception was rice, where it decreased by 23% at MTDP due to shortage of irrigation supplies. Maximum yield increase was observed in CCADP for cotton (80%), sugarcane (94%), wheat (67%); and at MSP for rice (46%). For chilli the maximum increase (147%) was observed at MTDP study site. Low increase in the yield was attributed to the shortage of irrigation supplies during the post-project periods. Limited sub-irrigation resulting from the operation of subsurface drainage systems was also observed to be another factor for low crop yields. Overall quantitative comparison indicated a positive impact of drainage system installation in terms of crop yield improvements.
