Rapid invasion of Water Hyacinth plant threatens Ethiopia’s Lake Tana

The world’s fastest growing plant is harming the fishing industry, agriculture, and local tourism in northwestern Ethiopia, the source of the Blue Nile.

Story and Photos by Dagim Terefe
Editing and Visualizations by Annika McGinnis
Coordinated by Fredrick Mugira


  • Lake Tana in northwestern Ethiopia is infested with water hyacinth, a fast-growing invasive water weed native to South America.
  • The lake is one of Africa's most unique wetland ecosystems and the source of 50 percent of Ethiopia's freshwater. UNESCO designated Lake Tana as a World Heritage site for its unique ecological biosphere reserve in June 2015.
  • Since it was introduced to the lake in 2011, the weed has grown exponentially to cover about 40 thousand hectares. Agricultural pollution, urban pollution and degraded land due to free grazing are cited as major factors contributing to the weed's growth.
  • The weed is destroying the fishery industry, destroying maize, rice and 'Teff' crops, making cattle sick, clogging canals of hydroelectric power plants and creating serious environmental imbalance.
  • Universities, authorities and other concerned bodies have been mobilizing people all over Ethiopia to remove the weed by hand, though it is expensive and time consuming. A potentially better strategy is biological control - using natural enemies such as insect and animal species that fight the weed - though it has not been used extensively in Lake Tana.

Habte Tefera is a fisherman living at Amhara National Regional State, South Gonder Zone, Fogera Wereda, Nabega Kebele, on the shores of Lake Tana.

He has been fishing for over 20 years. He leads 9 family members.

"Fishing could make me to buy 2 motorboats, 2 milk cattle before," Habte said. "I am getting nothing today. The resource of Lake Tana has been destructed by the water hyacinth.","This invasive water hyacinth, ‘Enboch,’ is very dangerous. Even though it came here in recent years, it is highly affecting the communities’ lives right now," Habte said.

Today, in fact, Tana is critically infested with water hyacinth, Eichhornia crassipes, locally named as 'Enboch,' an exotic, free-floating invasive plant that is native to South America.

The invasion is putting the aquatic biodiversity of Lake Tana at extreme risk. The vast swathes of the water around the lakeside South Gondar Zone of Fogera Wereda are becoming a sea of green. Fish pens and navigation channels alike are clogged by an impenetrable mass of water hyacinth.

It is shocking when anyone sees the amount of water weed that has covered the wide area of Kebeles on the shores of Lake Tana.

Not only is the lake important as a water source for over 123 million people in the Nile Basin, it is also a source of food in the form of fish, livestock, and agriculture. But weeds are threatening this life-giving resource.

According to the researchers, the weed could cover the whole lake in a few years’ time if immediate control strategies are not in place.

They noted that it can destroy the fishery industry, create obstacles to navigation, clog canals of hydroelectric power plants and generally create serious environmental imbalance.

Visualization by Annika McGinnis of InfoNile

Visualization by Annika McGinnis of InfoNile


Photo by Dagim Terefe

Photo by Dagim Terefe

Studies show that the water hyacinth weed was first introduced into Africa through Egypt sometime between 1879 and 1882.

It has been recognized as the most damaging aquatic weed in Ethiopia since its first presence in 1965. Its presence has been recognized in Lake Tana since 2011.

Dr. Ayalew Wondie is an Associate Professor of Aquatic and Wetland Science at Bahir-Dar University. He was “shocked” when he found the weed in Lake Tana in 2011 and studied its "great impacts on Lake Tana wetlands and ecology," he said.

While the source of the weed in the lake is still unknown, some potential originators are migratory birds, used and contaminated fishing materials from neighboring countries, and the use of water hyacinth as an ornamental plant, Dr. Ayalew said.

Studies show that water hyacinth has a stupendous capacity and its rate of growth is said to be highest of any aquatic or terrestrial plant on earth.

Two plants can produce 1,200 plants in four months, and the weed can cover an area doubled its size in 12 days. It is estimated that 0.405-hectare may contain 650,000 plants with a bulk weight of 200 tons, according to aquatic researchers.

"The coverage of the water weed was estimated at less than 10 hectares in the year 2011 at the convulsion point of river 'Megech' with the lake. At same year, 15 Kebeles were immediately infested by the water weed. It reached to 20,000 hectare at the end of 2011," Dr. Ayalew said.

Pollutant chemicals from agricultural land and urban areas are a major factor aggravating the hyacinth's expansion in Lake Tana.

"There are intensive agricultural activities at 'Dembiya' and 'Fogera,' which rush out and drain the used pesticides and fertilizers to the buffer zone whereby water hyacinth gets its nutrient for growing," Dr. Ayalew said.

Urban pollution is another critical factor spreading water hyacinth in the lake.

"100% of municipal waste of Gonder city is discharging into 'Megech' river - Lake Tana without treatment. 80% of municipal waste of Bahir Dar city drains to the Nile River ('Abay') and 20% of it drains to Lake Tana. There is no green belt or buffer zone at Lake Tana to protect waste matters. It facilitates the spreading of water hyacinth. So we have to stop and think over it," Dr. Ayalew warned.

The degraded buffer zone land due to free grazing and recession agriculture also helps water hyacinth to flourish, according to Dr. Ayalew.

This Juxtapose compares satellite imagery from 2010 and 2018 to show the invasion of water hyacinth in Lake Tana in recent years. Drag the scroll bar to the left to see the change over the years. Created by Annika McGinnis

Even though a tremendous amount of human labor, time and money was dedicated by surrounding communities and the university to remove the weed, coverage continued to escalate and reached to 40 thousand hectares, especially between 2015 and 2017.

The specific amount of coverage decreases or increases based on the hydrological season: "The coverage would be reduced to 2,000 hectares during dry season and exceeds to 50,000 hectare during rainy season," Dr. Ayalew said, though Mezgebu Dagnew, director of ‘Enboch’ Weed Removal Directorate at Amhara Regional State Environment Bureau of Forest and Animal Resource said that the coverage is up to only 5,396 hectares.


Photo by Dagim Terefe

Photo by Dagim Terefe

Lake Tana is a shallow lake with an average depth of 8 meters.

Around, 40 rivers including the Blue Nile locally named as 'Tikur Abay' and streams flow into Lake Tana from its large surrounding watershed area of about 15,000 km.

The lake is one of Africa's most unique wetland ecosystems and the source of 50 percent of Ethiopia's freshwater, located in the Amhara Regional State of the northwestern part of the Ethiopian highland.

The lake has been listed in the top 250 lake regions of Global Importance for Biodiversity. It has 28 species of fish, of which 21 are endemic. Commercially, the lake’s most important fishes include the large African barbs, Nile tilapia and African catfish.

The annual commercial value of fish production at Lake Tana is estimated at about USD $1.1 million.

Recent studies show that the potential fish production of the lake is estimated to be 13,000 tons yearly- but its current fish production is less than 1,000 tons a year. It shows a serious decline in fish stocks due to the spread of the aquatic weed around fish spawning grounds.

"The water body is very cold which is covered by the water weed. Fish needs sunlight for breeding. While fishes move to the shores of the lake for breeding, the shores would not be conducive due to water hyacinth mats," Habte said.

Studies also noted that the weed mats sealed off breeding, nursing, feeding, and fishing grounds for various inshore fish species.

The water hyacinth mats have blocked light, severely reduced oxygen levels, and allowed poisonous gases, such as ammonia and hydrogen sulfide, to accumulate.

Water hyacinth mats have further invaded fishing grounds and blocked waterways in Lake Tana.

For fishermen, the hyacinth mats reduce their catch by covering grounds, delaying access to markets because of loss of output, increasing fishing costs because of the time and effort spent in clearing waterways, forcing translocation, and causing loss of nets.

"Since the water weed invaded Lake Tana, the production of fish has been decreased and the price has been inflated. The known taste of fish has also been changed. I have realized the different tastes in between where 'Enboch' occurs and not," Habte says.

The Faculty of Agriculture and Environmental Sciences, Department of Forestry, Debre Tabor University research finding has also proved that water hyacinth is perceived to affect fisheries through reduced levels of production, a reduction in species diversity, poor quality fish, and rising costs of operation resulting in lower income to fishers and higher prices to consumers.

Mr Birhanu Wubnhe lives in Gondar city. He has been working in fish trading for the last 12 years.

He has promoted modern fishing systems within five Woredas where water hyacinth is currently infested. He is a vibrant and strong environmentalist in advocating the regional government and research institutions to prioritize the communities’ cultural and indigenous knowledge in order to remove the weed.

"Water hyacinth has destroyed our ecology and thus fish resources. Wetlands have been dried," Birhanu says. "There was a trend of controlling 'Enboch' from the year 2011-2013. But due to the fact that absences of continuous follow up, the coverage has been reached from 4 Kebeles to 18 Kebeles starting in 2013 onwards."

Lake Tana was generating various employment opportunities for local residents, especially in the fishing industry in the town of Bahir Dar. Fishermen were selling to hotels, restaurants, lodges and more. However, now, the notorious weed has been shadowing the hope of the surrounding communities.

Visualization by Annika McGinnis

Visualization by Annika McGinnis


Photo by Dagim Terefe

Photo by Dagim Terefe

Worknhe Tsega is a farmer living at South Gonada Zone, Fogera Wereda, Nabega Kebele.

He also serves Nabega Giorgis Church as a priest. He expressed his sympathy over the impacts of the notorious water hyacinth on Lake Tana.

"We were harvesting maize, rice and 'Teff' crops before. But the whole shores of Tana have been covered by 'Enboch.' The farmers are getting nothing except their tiredness," Worknhe said.

"Farmers were getting high agricultural products before. We were delivering agricultural productions to the market. But starting the water hyacinth came over here we cannot even feed ourselves. The farmers are becoming poorest," Worknhe said.

Agriculture is the mainstay of the Lake Tana sub-basin economy. More than 80 percent of the cultivated land during the base-year is under a rain-fed system, and the remaining is cultivated using irrigation and residual moisture, respectively. The farming system is characterized by a crop-livestock mixed production system.

"When cattle eat the water weed they become pained and finally die," Habte said. "The government is not giving enough support to the farmers. This Wereda is known as 'Golden Fogera' in its productivity. Our cattle have been eating the water weed and thus dying. So the regional government should support the Kebele’s administration and farmers."

Deacon Alemu Belachew is an administrator of Nabega Kebele, Fogera Wereda in South Gondar. He called on the regional and federal governments’ support to remove the invasive weed.

“It is difficult to remove ‘Enboch’ just by human power. Even though we have been striving to remove the water weed by mobilizing the communities starting in 2017, the water weed is spreading at alarming rate.  So if the expansion continues, Nabega Kebele will not stay longer. If the government does not take an immediate measure, the whole communities estimated from 3-4 thousands in the Kebele will be affected, Alemu said.


Dam on the Blue Nile near Bahir Dar, Ethiopia. Sourced from Wikimedia Commons

Dam on the Blue Nile near Bahir Dar, Ethiopia. Sourced from Wikimedia Commons

Lake Tana has global importance, originating not only from a biodiversity perspective but from a hydropolitical point of view, being the source of the Blue Nile River.

The weed has the potential to clog canals of three irrigation dams known as 'Rib,' 'Megech' and 'Megech Serba' that supply power for Ethiopia and surrounding countries, according to researchers Goraw Goshu and Shimelis Aynalem.

"These projects are being implemented on the infested ecology. If the spreading speed of water hyacinth continues, we will lose a billion dollars’ projects," warned Birahnu Wubnhe, a local environmentalist.

About this Map: The growth of the invasive water hyacinth plant has expanded drastically in recent years in Lake Tana. Urban pollution is a major factor, with 100% of municipal waste from Gondar city in the north and 20% of waste from Bahir Dar city in the south draining to the lake. Intensive agricultural activities at Dembiya and Fogera also drain used pesticides and fertilizers to the lake's buffer zone, which quickens the growth of the hyacinth.

As Lake Tana is the source of the Blue Nile - which supplies about 60% of water in the entire Nile River - the weed also has the potential to clog canals of three irrigation power projects known as ‘Rib,’ ‘Megech’ and ‘Megech Serba’ that supply power for Ethiopia and surrounding countries. Map created by Annika McGinnis.

“We are observing lack of integration, accountability, and business as usual works among the government- especially, there is lack of capacity in the regional Environment Protection Bureau. They do not know the lake properly. They don’t have open ears. They cannot take recommendations positively which may bring tangible solutions on the ground," Birhanu said.

Some experts question what the federal government is waiting for.

The Grand Ethiopian Renaissance Dam is being built with the full participation of the Ethiopian people.

'Why do we construct the dam if 'Emboch,' which is a water thirsty plant, is diminishing the water flow to the dam?' is a critical question of various experts.

Some environmentalists warn that water hyacinth does not respect man-made boundaries and hence primarily it should be the responsibility of the Ethiopian federal government, and second the downstream countries.

In particular, since the plant may spread to downstream countries, Sudan and Egypt should be consulted to see if they can contribute something to help the Nile’s water flow smoothly.

"This plant is water thirsty, hence first it minimized and later it depleted the flow of the Nile water. If the problem persists, GERD and Nasir dam will be empty!" environmentalists warn.


Photo by Dagim Terefe

Photo by Dagim Terefe

Lake Tana has a unique religious, historical and aesthetic value with 37 highlands and many monasteries and churches dating back to the 13th century.

Visitors to the monasteries of the Ethiopian Orthodox Tewahedo Church also make up a huge source of revenue in tourism for locals and government.

The lake is also believed to be a source of knowledge and ancient Ethiopian wisdom and glory. These churches and monasteries contain valuable treasures of the Ethiopian Christian faith.

Historians label Lake Tana a mystical place where time and history run deep.

Some of these churches have managed to protect a few patches of original forest vegetation.

These remnant church forests are islands of biodiversity, providing refuge for over 100 tree and plant species, many of them indigenous and rare. These sites are invaluable pools of genetic resources, for example of wild coffee and field crop varieties.

The United Nations Educational, Scientific and Cultural Organization (UNESCO) designated Lake Tana as a World Heritage site for its unique ecological biosphere reserve in June 2015.

The water hyacinth invasion is a major threat to sustaining the lake’s biodiversity.


Photo by Dagim Terefe

Photo by Dagim Terefe

Though a water hyacinth infestation is very difficult to get rid of, Dr. Ayalew Wondie and other wetland scientists noticed that globally, there are three ways to do this: removal (manual and mechanical), chemical spraying (using herbicides) and biological control methods.

Manually removing the hyacinth is advisable when the scale of infestation is at minimal level, but it doesn’t work in Lake Tana where the coverage is so widespread, according to Dr. Ayalew.

He said removing the weed using chemicals is also unadvisable because "people drink the water, use it for sanitation, and livestock."

Biological control, which uses natural enemies such as insect and animal species that fight the weed, has been more widely used.

It is low-cost and usually has no negative environmental impact, making it a more effective approach to manage water hyacinth in the long term, according to experts.

Two weevil – or beetle – species, Neochetina eichhorniae and Neochetina bruchi, have been widely used against water hyacinth with success, studies indicate.

In the world, 33 countries have shrunk the coverage of the weed and controlled its spread by using biological control methods, including the United States, Uganda, Nigeria, Ghana, India and Australia.

But this method takes years of work by the insect to clear the weed. For instance, the weevils took two years to control the weed at Lake Victoria in Uganda.

In Lake Tana, controlling the weed through such means is also difficult because "water hyacinth did not come here with its natural enemy," Dr. Ayalew said.

Further, removing the weed by hand or with machines is expensive and time-consuming.

Universities, authorities and other concerned bodies have been mobilizing people all over Ethiopia to remove the weed by hand, especially starting at the end of last year when the problem get coverage on social media. But this happens only when the lake shores are accessible and when farmers have time and are given incentives by the government.

Even though Dr. Ayalew believes that biological method is the most effective, he fiercely recommended removing the weed manually in order to avert the extreme expansion of the weed and its negative impacts on many economic, social, and ecological resources.

"As long as I live on the shores of the lake and know the problem, it is possible to remove the weed by using fishing mats and boats," Wubnhe said.

But according to environmentalist Birhanu Wubinhe, there are two main challenges with this strategy.

"One-the Regional Bureau of Environment, Forest and Animal Resource is not interested to use our cultural knowledge. Second- the removal works of water weed are being done by volunteer farmers. But the Bureau doesn’t pay incentives for motivation," Wubinhe said.

However, according to Mr. Mezgebu, as of yet there is no tested and functional method to control the weed based on indigenous knowledge.


Photo by Dagim Terefe

Photo by Dagim Terefe

Dr Ayalew Wondie has been conducting research works on methods of controlling the water hyacinth.

In this respect, he focused on synthesizing the fragmented local communities’ cultural or indigenous knowledge.

"I observed [that] a farmer fences his farmland by Cypress plant in order to protect the crop land from the infestation of the water weed. This tells me that if we apply such method, we can control at least further spreading of the water weed instead of eliminating or removing the weed," he said.

“As a pilot project, I took a degraded site and planted Papyrus tree. Papyrus grows in structural unit within 3 months and is able to protect the expansion of water hyacinth,’’ Dr Ayalew said.

However, according to Dr. Ayalew, governmental extension groups were not willing to take these pilots into their day-to-day activities.

"I have prepared guiding manual which could support the extension workers and communities. It compiled the whole biological features of the water weed so as to control the spreading of the water weed," Dr. Ayalew said, warning that "if we failed to control the water weed, the lake which 2/3 of it is a wetland may be aged and change to terrestrial land."

Even though various research institutes and researchers have been conducting research works to control the water weed, we have not disclosed the results due to they are still in testing phases," said Mezgebu Dagnew, director of 'Enboch' Weed Removal Directorate at Amhara Regional State Environment Bureau of Forest and Animal Resource.

He stressed that it is important to make the community aware of strategies to control the weed in order to make them create their own fencing using the papyrus plant.

Instead of focusing on removing the weed using harvesting machines, Dr. Ayalew recommended that the government should exploit the communities’ cultural or indigenous knowledge through giving them incentives.

"The local communities are suffering in the lake while they are struggling to remove the water weed. They are infested by snakes, hippos, and so many other dangerous insects like leech. Mass mobilization without incentive, orientation, preparation, and actual removing schedule is ineffective," he said.

"The regional government and relevant stakeholders have to think to bring alternatives. We can develop tourism, fishery and animal forge on the ecology as alternatives.

"There should be proper land use management. Free grazing makes the footprint of the cattle bury the seed of water hyacinth inside the sediment, which could give a chance for the water weed to stay over 20 years in the sediment and then grow again,’’ Dr. Ayalew said.

Birhanu Wubnhe, an environmentalist, said that it is important to take out the issue of water hyacinth from political and business interests and give the issue to the proper person who knows the problem and can genuinely work to avert it.

"There should be an independent project office which will be lead [by the] regional government and strongly work on controlling the water weed, instead of giving multi-tasks to regional Bureau of the Environment, Forest and Animal Resource," Dr. Ayalew said.

"The issue of Lake Tana is number one in the region," he said. "If so, it should be lead by regional number one head. It should also be given to the actual professionals than politicians only."

This project was made possible with support from InfoNile and Internews' Earth Journalism Network. © InfoNile July 2018.