gpa_east_africa_case.. - GRID Africa GeoPortal - UNEP

sea grass beds are able to soak up nutrient influxes from the coast and therefore provide aline of protection for the coral reef (SETOI, 1990).The release of polluted water as a result of houses, hotels and stock raising farms mayinduce acute toxicity to the hard coral species resulting in bleaching and a shift in the coralreef ecology making conditions more favourable to soft coral species. Steadily the fastgrowing soft corals enter in competition with the slow growing hard ones that are very sooncovered and killed by the blanket of soft corals.ImpactsHealth and sewageThe problem of sewerage and the human health impacts resulting from inadequate disposalmethods is a multi-sectoral problem in Seychelles. Increasing affluence in Seychelles and theexpansion of the middle class population have resulted in conversions of former plantationsand even hilly areas into housing estates and dispersed residential units. Although theproblems of sewerage have been recognised by planners, the problems of disposal havegrown. In addition, all the construction activity in particular on hilly slopes results in majorerosion of red earth. The result is that when major rains occur heavy sediment loads andother associated contaminants such as nutrients and bacteria associated with wastewater areflushed into the sea. This runoff may be a significant public health risk in the future.Up to now, there is little evidence of medical problems associated with contamination due tosewage in the Beau Vallon area.Water-borne diseasesWater-borne diseases from contamination is not a major issue compared to other countries inthe region. However, there are still ongoing problems with certain intestinal parasites. Duringthe 1990-2000 period the Ministry of Health implemented a programme, sponsored by WHO,on intestinal parasite control in school children. The programme has also sensitised childrenon habits of personal hygiene and the level of parasites has decreased significantly in thatage group.Potable waterWith continued improvement in piped water supply coverage, there has been a noticeablereduction in the use of streams and rivers as water sources for drinking. However,contamination of water sources continues. Potable water sources or the Beau Vallon areacome from the Rhodas and Le Niol rivers. The surface water at the inlet of both Rodhas andLa Niol Rivers have been found to be polluted from non-point sources such as householdseptic tanks. The sources of such pollution are undoubtedly associated with humansettlements further upstream. The water quality immediately downstream from the Le NiolWater Treatment works which treats water from these two rivers, is virtually the same.However, as the river passes human settlements and farms on its way to the sea the pollutionload increases (Shah, 1997). The figure below illustrates the water quality of these rivers.Water Quality of surface river water at Le Niol Treatment Works inletAnalysis Rodhas River Le Niol RiverPhysicalAppearance Clear ClearColour (Hazen) 0-15 5-100Turbidity (NTU) 0.5-5 0.5-5Conductivity (µs/cm 20-100 20-100Total Solids (mg/L) 30-150 50-300BacteriologicalTotal Coliforms (CFU/100ml at 35°C) 10-200 10-200E.coli (CFU/100ml@44.5°C) 10-200 10-100Faecal streptococci (CFU/100ml@35°C) 5-30 5-20Source: PUC, 1998Final Draft Report – Cost Benefit Case StudiesGPA Strategic Action Plan on Sewage, October, 200094