This paper presents a case study in Usangu Sub-basin, Tanzania, investigating the relationships between irrigation water management, rice productivity, and malaria incidence. The information was gathered for two paddy growing seasons from two types of irrigation systems namely large/modern and smallholder irrigation systems. The number of days that water spent in the fields and their respective daily depths were recorded for each season. Further, the annual volumetric water use for different irrigation systems were monitored from three selected sample fields. The average rice yields were then computed from each trial field and the productivity of water in Kg of paddy per cubic metres of annual volumetric water use was worked out. On the other hand, malaria incidences were recorded for two different age groups in the area with their respective occurrence period. The relationship of malaria incidence and its pattern to peak activities in the fields were used to assess the loss in rice productivity. The result suggests that there is a significant contribution of high depth flooding technique (up to 25cm), to increased malaria incidences, water losses and low productivity of irrigated water in the study area. A loss of up to 8% in rice productivity was estimated to occur per single malaria attack in wet season. In addition the findings suggest that about 40% of the water could be saved from large irrigation systems through intermittent irrigation and an obvious reduction in malaria breeding and without necessary affecting the rice productivity.
Paper presented at SIMA Special Seminar during the 3rd MIM Pan-African Malaria Conference, 17-23 November 2003, Arusha, Tanzania. 9 pp.