A comparative assessment of selected raw water intake systems in Rwanda

Abstract

After the genocide of 1994, Rwanda has been struggling to contain urban migration and its pressures on existing facilities. Water supply coverage is low at 76% in urban areas and 68% in rural areas. This implies that huge investments are required to meet the Millennium Development Goals on water supply and sanitation. This study was conducted to assess the existing problems of raw water intake systems at Yanze and Nyabarongo intakes in Kigali; Shyogwe intake in Ruhango District; and Kadahokwa intake in Huye District. The study was in response to high amounts of sediments in raw water which literally clogged the intake systems for a number of days, resulting in erratic water supplies to the residents in the rainy season. The study focused on performance problems of the intake systems, raw water turbidity variations and the assessment of how environmental concerns could be addressed in the design of intake systems in areas of high soil erosion activities. Data was collected through interviews and physical measurements. The study revealed that flooding, intake site selection, erosion, screen clogging, intake protection, high raw water turbidity, inadequacy of raw water supplied to the water treatment plants, and low downstream environmental flows were the main intake problems. The Yanze intake had worst problems with high levels of flooding, erosion, sedimentation, and high raw water turbidity levels. The bank filtration system at Nyabarongo gave the least problems of raw water turbidity. Yanze and Nyabugogo river intakes systems were found to be threatened by decreasing water levels attributed to surrounding upstream landuse activities. It was recommended that proper maintenance of existing structures, landuse management around river intakes, use of well-designed reservoir abstraction systems, increased groundwater abstraction systems (including bank filtration), would greatly improve the performance of intake systems in Rwanda.