Water Professionals’ Day Symposium – October, 2005 Deviation of Planned Water Demand from Actual on Farm Water Usage and Suggestions for Improvements: A Case Study from Uda Walawe Irrigation Scheme, Sri Lanka Priyantha Jayakody, François Molle and M.M.M. Najim Abstract Water managers’ seasonal water allocation plans deviates from the actual water usage in the field due to many factors. Temporal and spatial variations that vary dramatically will affect the Field Irrigation Requirement (FIR) which is calculated. Therefore, the main objective of this paper is to see how planned FIR deviates from the actual on farm water usage in Uda Walawe Irrigation Scheme. The study proposes suggestions for improvements in meeting and balancing the water demands. Irrigation issues and the interviews with farmers and officials were used for the analysis. Results show that actual water usage is always higher than the FIR and water manager’s planned. There are various factors contributes for these discrepancy. Two lines of improvement are outlined. One is adjustment of the volumes allocated to each D. The second possibility of improvement points to greater involvement of farmers at the scheme and branch levels. A way to tackle this is to devise a transparent process of allocation at the scheme level whereby representatives from the different branch canals would participate in the definition of sharing arrangements. MASL’s role would be to ensure bulk allocation at the head of canal. FOs are responsible for finding ways to distribute this volume within their area. Introduction Irrigation water management is a critical issue in this millennium as available water is to be allocated for various other uses. Competition for water has been increased and the share for agriculture has reduced. Intensive planning and management is necessary to overcome the frequent crop failures. Water managers calculate on farm water demand using various assumption and methodologies but some time they cannot achieve their target and there are various reasons for that. Udawalwe Irrigation scheme (UWIS) is a good site to understand these reasons. This paper highlights difference between water managers planning and the actual implementation at the ground. Uda Walawe development scheme is one of the major multipurpose development projects implemented by government of Sri Lanka after the independence. The Uda Walawe reservoir is located on the boundary of the Wet and Dry Zones of Sri Lanka (Figure 01), around 200 km southeast of Colombo (Hussain et al. 2003).