Irrigation Performance Improvement by Non-Structural Measures — A Case Study from Bangladesh

Potential performance of an irrigation project rarely attains its optimum level. The causes may be deterioration of physical condition of infrastructures, non-optimal operation of water control structures, inadequate conveyance of the irrigation system, excess withdrawal at upstream, lacking of optimal managerial and operational irrigation schedule. The effect of these results reduced crop-yield. The Meghna-Dhonagoda Irrigation Project (MDIP) is one of the aspirant irrigation projects in Bangladesh. The Project area comprises 17584 hectares of which 14602 hectares are cultivable. Irrigation water is supplied by withdrawing water from river by two pump houses. The Project was implemented during 1978 to 1887. Since inception only 50% of irrigation performance was receiving from more or less reliable supply of water and the same was declining over the years. Among all constraints it was conceptualized that the practiced irrigation schedule and operational management were the main obstacles to attain its optimum result. It is found that over the total crop period the Crop Water Requirement (CWR) is considered as fixed depth of 265 mm/month, which causes the scarcity of water in the land preparation and flowering stages, on the other hand misuse of water in the matured and growing stages. The causes of this type of irrigation schedule is due to physically based problem of irrigation canal system, pump operation, land use and variety of cropping pattern in the same season. Since 2000, people's participation, a non-structural measure has been practicing to overcome these problems. By people's participation irrigation performance was improved up to some extant (up to 70%). To attain the maximum potential irrigation performance, a new strategy of staggered cropping pattern, is recommended. Another non-structural measure is Application of Decision Support System (DSS) for improvement of irrigation performance. A GIS based DSS, MDIP-DSS, developed by Bangladesh Water Development Board (BWDB) in 2000, which integrates with MIKE-11 HD and MIKE-SHE models. With this MDIP-DSS, an optimised scenario has been simulated for pump operation and gate operation of the water control structure for MDIP. Analysis shows the best simulation can increase the dependable irrigation index up to 82% and the highest average index up to 92% for high yielding variety Boro rice in MDIP. Combination of both of these non-structural measures will give more improvement of the irrigation performances in any irrigation project.