Published: 30 August 2017
To some, the water hyacinth weed (Eichhornia crassipes) is a blessing. But to others, the weed is loathed and it’s a menace. The weed is one of the most sensitive environmental issues currently affecting Lake Victoria Basin and its surroundings. Lake Victoria has been the habitat of a large variety of fish species and diverse variety of medicinal plants, according to Prof. Raphael Achola Kapiyo, an Environmental Scientist at UHAI Lake Forum.
To a section of fisher-folk, water hyacinth weed is a blessing because it creates a naturally protected fish breeding ground, and many lost fish species have reappeared. At the initial arrival of the weed, fishermen used to make appeals to the government to speed up its removal but later realized that it has immense economic potential.
They claim that the weed has created favourable breeding ground for various fish species that had disappeared from the lake in 1970’s due to intensive fishery activities.
Prof. Kapiyo observes that in 1990s species such as Barbus (fuani), labeo (ningu), synodontis (okoko), Mormyous (okunga) and Schilbe (sire) re-appeared with the emergence of water hyacinth weed. To fishermen, the weed has also improved the breeding of species that like low oxygen concentrations like prototerns (kamongo) and clarius (mumi). When the weed became a menace to the communities around the lake in 1990s, Kenya Government contracted an American aquatic company to harvest the weed, a move that was met with a strong opposition by the civil society in Kenya. Scientists claim that the depth of Lake Victoria was shallow and the harvested weed should not be allowed into the bed of the lake. Prof. Kapiyo has led the local communities through the UHAI initiatives and warned on the biodiversity loss and depletion of the resource that threaten their livelihood. Water hyacinth is difficult to control in all freshwater aquatic environments. When access is limited by the presence of the weed itself, control becomes more difficult, Prof. Kapiyo says.
Scientists say water hyacinth is one of the world’s aquatic weeds that infest rivers, dams, lakes and irrigation channels on every continent except Antarctica. It devastates aquatic environments and cost billions of dollars every year in its control costs and economics losses.
The water hyacinth has its origins from the Amazon Forest in South America. It has spread rapidly across the world because of its beautiful violet and purple ornamental flower. As an invasive and alien species outside the Amazon, the water hyacinth has been classified by the International Union for the Conservation of Nature (IUCN) as one of the 100 most aggressive invasive species, one of the top worst weeds, and indeed the worst water weed.
A Tanzanian Scholar, Prof. Mark Mwandosya says water hyacinth has led to destruction of biodiversity; prevention of oxygen transfer from the air to the water surface; reduction of water quality; clogging of waterways hence hampering transport, hydropower, agriculture, fisheries, tourism and recreation; and an increase in pests and water borne vectors causing malaria, typhoid, dysentery, schistosomiasis, rift valley fever, E coli infection, bilharzia, and cholera. The blockage of waterways by the water hyacinth renders many areas infested by the weed prone to flooding.
First seen in Egypt in the 1890s the water hyacinth has spread along the full length of the River Nile Basin such that by the 1990s it had covered much of the coastline of Lake Victoria, Prof. Mwandosya says. Control measures against the water hyacinth have included: mechanical and manual removal of the weed; chemical control through use of herbicides; biological control through the introduction of weevil beetles (Neochetinaspp) and water hyacinth moth species.
The aforementioned measures have been applied towards the control of the weed in Lake Victoria through the the Kenyan National Discourse partner, Lake Victoria Environment Management Project (LVEMPII) under the support of the World Bank. An LVEMPII initiative through Lake Victoria Basin Commission undertakes the control of the weeds in the five East African states of Burundi, Kenya, Rwanda, Tanzania and Uganda. The term control is used to signify the difficulty of eradicating the weed. Its spread can be minimized at a particular place only to appear at another location later. A basin-wide approach to the control of the water hyacinth on a long term and sustained programme could be economically beneficial measure against the costs of dealing with the negative effects of the weed.
Water hyacinth can rapidly take over entire waterways. Under favorable conditions it can double its mass every 5 days, forming new plants on the end stolons. It grows from seed which can remain viable for 20 years or longer.
Water hyacinth was reported in Lake Victoria basin in Kenya in 1991 and has since become a menace in many beaches in Winam Gulf, Nyando, Yala, Nzoia and Gucha Rivers.
Efforts to address the hyacinth problem
To address the water hyacinth problem, the Lake Victoria Environmental Management Project II is undertaking both preventive measures targeting the watershed, waste treatment facilities from industries and towns, and curative measures targeting the lake and other water bodies within the basin. Curative measures intend to employ an integrated approach involving:- (i) biological control methods using weevils and mites; (ii) manual removal using communities adjacent to the infested beaches; and (iii) mechanical removal using motorized machinery at piers , water intake points and other beaches where the equipment can operate effectively.
A baseline survey undertaken in December 2010 estimated the water hyacinth mat in Lake Victoria and other key water bodies to be approximately 10,000 Ha. Several beaches across the lake are infested with water hyacinth weed.
The East African Community (EAC) Sectoral Council of Ministers sitting in Kisumu on January 2011 noted with concern the severe infestation of water hyacinth that is a source of environmental stress on the Lake and the inherent negative socio-economic impact at Kisumu pier and Winam Gulf in general. The council directed LVEMPII to activate earlier resolutions of the council in dealing with the water hyacinth menace in the Gulf.
The National Project Coordination Team (NPCT) prepared a strategy to implement the directive of the council of Ministers to manage the water hyacinth in the Winam Gulf as an emergency measure. The team identified Kisumu Port, Kendu Bay and Homa Bay piers, Kichinjio, Usoma, Kusa, Sangorota, Rakwaro, Ngegu and Koginga beaches as the most severally infested areas of the Gulf.
The author is Mr. Peres Wenje, the NBD National Technical Support Expert / Kenya