Starting from 1989s and due to an accidental species introduction, Lake Victoria has undergone the most severe infestation of water hyacinth with significant socio-economic impact on riparian populations. The relevance of Lake Victoria for the economy of the region has been recognized by FAO so much so that it promoted an international project named Lake Victoria Environment Management Project (LVEMP, Klohn and Andjelic, 1997) in order to rehabilitate the Lake ecosystem via water pollution control, water catchments protection enforcement of water quality, periodic monitoring and assessment of water resources. The infestation of the water hyacinth has been particularly severe along the northern and eastern shore-lines and islands (Uganda and Kenya).

In particular, the Winam Gulf, located in the Kenyan sector of the Lake, was interested by the highest infestation of water hyacinth in 1998.Troubles caused to fishery have a significant impact on the territory because, although fishery constitutes only a small percentage of the Gross Domestic Product, it is an important source of livelihood for many riparian communities. Aggressive efforts to fight the plant, including manual removal and the introduction of the plant’s natural predator (Neochetina weevil), combined with favourable environmental conditions helped reducing the weeds by 2000 (Wilson et al., 2007). However, images acquired by the satellite MODIS sensor in December 2005 and December 2006 showed a massive proliferation of water hyacinth in the Winam Gulf. According to NASA, this abnormal event could possibly be related to unusually heavy rains seasons that occurred in Kenya between 2006 and 2007 and that flooded the rivers that feed into the Winam Gulf. The rain and floods raised water levels of the lake and swept agricultural run-off and nutrient-rich sediment into the water. In this context, satellite remote sensing offers the capability to rapidly and synoptically monitor large water ecosystems and detect vegetation cover dynamics over time (Coppin et al., 2004).

To support the sustainable resource that represents the Lake Victoria for its surrounding countries and to help the Lake Victoria Environment Management Project, the objectives of this EOWORLD-2 project supported by the World Bank and European Space Agency is to make the best use of past, present and future Earth Observation technologies for the monitoring of different stages of human impact on the lake’s environment namely:

  • The evolution of the different human discharges (direct by waste waters or indirect by soil erosion) in the lake,
  • Its consequence in term of biological content (Chlorophyll-a, organic matter, turbidity that could impacts the flora on the lake’s bottom) due to excess or lack of nutrients in some part of the lake,
  • The proliferation of water hyacinths which is closely linked to this variability of nutrients fluxes.