Diagnostic Model Framework for Water Use in Rice-based Irrigation Systems

Abstract

"In this study, we present a framework for water use in rice-based irrigation systems. This framework intends to facilitate the improved understanding of the system's internal and external conditions for the productive use of the available land and water resources, and thereby create a reference for the system's physical, economic and environmental performance. Detailed attention is given to the analysis of constraints in the system focusing on hydrological, technical, managerial and economic factors. The development of a strategy for improving the system performance, especially its water productivity, is a priority for the use of the proposed framework. In a case study carried out at the Sakssou rice irrigation system, Coite de Ivoire, it was found that one cubic meter of depleted water produces 0.48 kg of paddy, which is about half of the estimated potential productivity of water. The depleted fraction is about 50 percent of water totally available to the system. Large quantities are utilizable but uncommitted outflow. In order to fully exploit the potential for improved productivity, a strategy, which follows four principal pathways is suggested: (1) improving the quality of services; (2) increasing the production per unit of water consumed; (3) reducing non-beneficial depletion, and (4) tapping uncommitted outflows. In the long term, an increase in water productivity to 0.9 kg of paddy per cubic meter is considered feasible taking a gradual strategy of short- and medium and long-term interventions. Uncommitted outflows from various system levels could be tapped and used more productively through harmonizing of water supplies and demand, improving canal flow characteristics, and re-establishing field storage and reuse during peak demand periods. A substantial contribution to increased water productivity could be made through the adoption of improved technologies and advanced cultivation practices such as new rice varieties, the use of mechanized farm equipment, a change from transplanting to direct seeding and better fertility management. From an economic perspective, the research suggests that concentrating on the first, more productive cropping season is beneficial and that a water conservation strategy should be adopted during the second, less productive cropping season. Thereby, sufficient storage can be carried over in order to sustain high production during the first cropping season of the following year."