Summary
 
Lake Victoria, one of the largest freshwater bodies of the world, is shared by three countries: Kenya, Tanzania and Uganda. The lake sustains important fisheries and is used for commercial navigation. The Owen Falls dam at its outlet allows for the use of regulated outflow for hydropower generation. Lake Victoria is one of the sources of the Nile, a river whose waters are heavily committed downstream. In recent years, environmental challenges have beset the Lake: the introduction of an exotic fish, the Nile perch, upset the ecological balance with harm for biodiversity, and a water hyacinth invasion has caused a host of problems. International cooperation around the Lake has a long history because of its significance as a source of the Nile and a major data collection and modeling effort took place in the 1960s and 70s. More recently, the countries that share the Lake have joined with the international community in efforts to manage and preserve its water resources, fisheries, and environment.


 
Physical and political background
 
Lake Victoria (see Figure 1) has a surface area of about 69,000 km² shared by three countries, with a land drainage area of slightly over 181,000 km² in 5 countries (Table 1). The mean depth is of about 40 m with a recorded maximum depth of 84 m and the volume of water stored is estimated at about 2,760 km³.

 
Table 1: Lake Victoria surface area, shoreline and basin area per country
 

 
The gross economic product in the lake catchment is of about US$ 3 to 4 million annually and supports an estimated population of 25 million people at average incomes in the range of US$ 90 to 270 per annum (1). Population density in the Lake basin is above the national average in all countries and the populations of the riparian communities grow at rates that are among the highest in the world.

Lake Victoria moved into the focus of attention in the 19^th century, when it was identified as one of the sources of the Nile. Because it has a control structure for a large hydropower plant at its outlet in Owen Falls, the Lake is classified as a very large reservoir. However, hydrologically the Lake behaves like a closed system, as can be seen in the water balance of Table 2. It takes about 73 years for a volume of water equivalent to the Lake to flow out of it Historically, somewhat above average rainfall in the early 1960s resulted in a sudden rise in water level of 2 m and extensive shore flooding. Since then, lake levels have receded to historic averages. Limnologically, the Lake is monomictic and primary productivity is high.

Figure 1: Lake Victoria and its catchment on Kenya, Tanzania and Uganda.

Table 2: Lake Victoria annual water balance 1965 - 1990
 

Water quality
 
The Secchi transparency index has declined from 5 meters in the 1930s to less than one meter in the 1990s. Pollution pressures are increasing and pollution impact by municipal and industrial discharges is visible in some of the rivers feeding the Lake and along the shoreline, such as the shallow Winam Gulf (Kisumu) and near Mwanza and Kampala. Among the sources of pollution are a number of basic industries such as breweries, tanning, fish processing, agroprocessing and abattoirs. Small scale gold mining is increasing in parts of the Tanzanian catchment, leading to contamination of the waterways by mercury.

Increased nutrient flows are coming mostly from rural areas. Fertilizer use in the farms of the region is limited and therefore it may be supposed that the nutrients are released from soil particles washed off the land by erosion, from burning wood-fuels, and from human and animal waste from the areas surrounding the Lake. From the urban areas, the main source is untreated sewage (2).

The increased inflow of nutrients into the Lake is resulting in eutrophication. Phosphorus and nitrogen concentrations have risen and algal growth has increased five-fold since the 1960s. A shift of algal flora composition towards blue-green algae is causing deoxygenation of water, health problems for humans and animals drawing water from the Lake, clogging of water intake filters and increased treatment costs for urban centers. Deepwater species have sharply declined and periodic upwelling of hypoxic water has caused massive fish kills.
 
 
Fisheries
 
The commercial fish catch is dominated by Nile Perch (60%), an introduced species that has expanded rapidly since 1978. The size of fisheries, which was of only some 100,000 tons in 1978, exploded with the introduction of the Nile Perch. Lake Victoria fisheries yields in recent years have been estimated at 300,000 to 500,000 tons per year. Sustainability of fisheries is threatened by overfishing, pollution and the ecological instability resulting from the introduction of the Nile Perch (1).
 
The need for fisheries collaboration in Lake Victoria was realized already in 1928. More recently, the three countries collaborated through the FAO Committee for Inland Fisheries of Africa (CIFA) Sub-Committee for Lake Victoria. A Convention for the Establishment of the Lake Victoria Fisheries Organization (LVFO), drafted with FAO assistance, was signed by all three countries in 1994. The LFVO will promote better management of fisheries on the Lake, coordinate fisheries management with conservation and use of other Lake resources, collaborate with existing bodies and programs dealing with Lake management, coordinate fisheries extension, advise on introduction of non-indigenous animals or plants into the Lake, and disseminate information on Lake Victoria. The newly established LVFO is currently supported by the European Union through the Lake Victoria Fisheries Research project.

 
Water hyacinth
 
The appearance of the water hyacinth (Eichhornia crassipes) in Ugandan waters of Lake Victoria was first reported in 1988. The source of infestation appears to be the Kagera river, the main tributary to the Lake, which drains also parts of Rwanda and Burundi. Owing to the predominance of southerly winds, water hyacinth is particularly dense in Ugandan waters on the northern shore, and the area between Entebbe and the Kenyan border has large floating mats. Water hyacinth interferes with fishing operations and commercial transportation services, increases the cost of water supply from the Lake, threatens the intakes at the Owen Falls power station, reduces fish in the Lake through de-oxygenation, and provides a preferred habitat for bilharzia hosts and vector mosquitoes for malaria (1).
 
FAO has provided assistance to the countries concerned in the assessment and in the establishment of the capacity to control water hyacinth in Lake Victoria. The control strategy is based on a biological control programme that relies on two weevil species that have been found effective world-wide. The main elements of the biological control programme are the establishment of mass rearing capacity, a coordinated field release programme, and monitoring performance. Biological control is not expected to overcome the problem totally and immediately. Thus, the control programme also relies on mechanical removal methods and on chemical interventions in restricted areas.
 
 
Water resources monitoring and management

All riparian countries have plans to use its waters for various purposes. Knowledge and understanding of the water regime in the Lake basin is a prerequisite for improving the capacity to sensibly manage the resource. Data collection efforts carried out in the 1960s and 70s under the WMO/UNDP Hydrometeorological Survey project provided a valuable crop of data but were interrupted owing to war events in the region. Currently, the need to catch up with the most basic infrastructure for water management is addressed through the regional FAO/Japan "Lake Victoria Water Resources (LVWR)" project.

The LVWR project has initiated the establishment of a sustainable skeleton network of rain gauges and river gauges for Lake management. Ground data will be integrated with remote sensing data in a geographically referenced (GIS) database. The database will be used through a water resources simulation model for spatial estimation of the rainfall regime, rainfall-runoff and river flow simulation, and a control/decision support system (DSS) for reservoir operation and water management. The DSS will assist the riparian countries in formulating a coordinated and mutually agreed upon management strategy for the Lake, and promote the institutional process within which the three countries will continue cooperation and interaction in Lake management.
 
A variety of options have been identified for configuring a tripartite institution for regional cooperation in the environmental management of the lake Victoria water resources and of its catchment (3). As the most effective approach, the Steering Committee of the LVWR project has undertaken steps to bring to the attention of the Permanent Tripartite Commission for Cooperation between Kenya, Tanzania and Uganda the need to incorporate representatives of the water administration of the three member states in any arrangement for tripartite cooperation in the water resources management of the Lake Victoria basin under the aegis of the Commission.
 
 
Environmental management
 
The natural resources of the Lake basin are used to obtain food, shelter and energy, to secure residential and industrial water supply and transport needs, for irrigation and to dispose of human, agricultural and industrial waste. In recent decades, with growing population and development, the multiple activities in the Lake basin have increasingly come into conflict and the Lake ecosystem has undergone substantial changes rendering the Lake environment unstable.
 
The Lake Victoria Environmental Management Project (LVEMP) is a comprehensive programme aimed at rehabilitation of the lake ecosystems for the benefit of the people in the catchment and the national economies of which they are part. The objectives of the programme are to:

(a) maximize the sustainable benefits to riparian communities from using resources within the basin to generate food, employment and income, supply safe water, and sustain a disease-free environment, and

(b) conserve biodiversity and genetic resources (World Bank, 1996).

The first phase of the project, with funding at the level of US$ 80 million by the Global Environment Facility (GEF), the World Bank, the three countries concerned and several donors, deals with fisheries management, water hyacinth management and control, management of lake pollution and water quality, management of land use in the catchment, management of wetlands and support for institutions for lake-wide research and management and pollution disaster contingency planning. Implementation of the LVEMP was initiated in mid-1997 and the first phase is to last five years (1).
 
 
Conclusions
 
Lake Victoria, for a long time seen mainly as a convenient reservoir for downstream water users, is now percveived by its riparian countries as an important resource that requires rational management to protect it from pollution and degradation. Kenya, Tanzania and Uganda have joined to assess the resources and the problems of the Lake, to develop management tools and to establish adequate institutions and capacity. Benefits will accrue to the population in the catchment, to the riparian countries and to the global community.
 
 
References

(1) World Bank: Staff Appraisal Report for the Lake Victoria Environmental Management Project, Report No. 15429-AFR, Washington, 1996.
 
(2) Bullock, A. et al.: Report on LVEMP tasks 11, 16 and 17, FAO, 1995.
 
(3) Burchi, S.: Institutional Options (revisited) for Lake Victoria Cooperation, Proceedings of the Second Regional Workshop of the LVWR Project, FAO/LVWR, Kampala, 1997.