The Invasion of Lake Tana

5 min readJul 31, 2020

By: Elbat Mesfin & Kabba Gizaw

Africa is a continent with many hidden jewels. The beauty nature has given the continent is remarkable. From the sand dunes in Morocco, the safaris in Kenya, and the national parks in Botswana, to the breathtaking views from the top of Mt.Kilimanjaro, there will always be amazing experiences awaiting visitors.

Lake Tana is one of these gems in Africa. Located in the Amhara region of Ethiopia, it is the largest lake in the country. It’s home to 50% of the country’s fresh water and contributes 60% to the Nile’s water. Its importance to the country and Africa is unquestionable. Lake Tana is the source of the Blue Nile, which is responsible for 70% of its floodwater at Khartoum.

The lake has a great importance from a social and economic perspective as well. It is a source of food to the surrounding community. The local economy heavily relies on fish production, specifically African barbs, Nile tilapia, and African catfish. Fish production from Lake Tana results in $1.1 million USD annually. Resorts surround the lake, taking advantage of its landscape and captivating beauty.

Lake Tana: taken by John Cowley (instagram: jsgcowley)

What’s wrong?

Unfortunately, Lake Tana has fallen victim to an invasive species — Water Hyacinths, indigenious to South America. Researchers aren’t exactly sure how they came to Africa, but human activity is most likely responsible.

This plant grows and spreads very quickly, restricting water flow. It creates an impenetrable barrier making navigation difficult. It also blocks sunlight, essentially suffocating any aquatic life. This negatively impacts the fishing industry, irrigation, and power generation. To prevent irreparable harm, the plant’s spread should be stopped before it covers the entire surface of the lake. Agricultural Researcher, Dereje Tewabe, explains that water hyacinth started from the Mitreha Abawarka Kebele of Gondar zuria with an estimated coverage of 3 hectares and the highest infestation of this invasive species covered approximately 80 to 100 hectares. Mr. Tewabe also notes that water hyacinth in Lake Tana is still in its infant stage; he warns that once it matures, it can spread even more quickly.

Water Hyacinth by Maya A. P from Pixabay

How to fix it?

Many methods have been researched and have proven to help eradicate and/or control water hyacinth.

1)Mechanical Control

One plausible solution is using machinery to physically remove water hyacinth out of infected areas in Lake Tana. While high-quality scientific instruments are quite expensive, these tools can quickly eradicate this invasive species without negatively impacting the surrounding wildlife and community.

However, it might be difficult to use such heavy machinery to reach broader areas of the lake where the water hyacinth spread. Most machinery might develop sensor related issues when used too far off the land, making it less effective.

This control is also labor intensive, adding to the total cost. According to Professor Michael J. Mara at the University of Georgia, the estimated annual cost of using mechanical control for a 400-acre lake was $13,500. As such, machinery should be employed sooner rather than later — the more this weed spreads, the more expensive it will be to combat.

2)Chemical Control

This method involves applying herbicides around the areas that are infected with this invasive species. Herbicides are used to execute displeasing vegetation through its toxicity. For example, glyphosate can effectively kill hyacinth weeds, while other herbicides such as sulfentrazone can control the spread of this invasive species. In order to eliminate ineffective solutions that might be more hazardous to Lake Tana and its surrounding community, the table below assesses the strengths and weaknesses of chemical control as a possible solution:

Table 1: The advantages and disadvantages of chemical control to eradicate water hyacinth.

While the use of chemical control to reduce the spread and growth of water hyacinth is a less labor intensive and more cost effective method, this herbicide will have long-term consequences on the overall health of the lake and the communities that depend on it for their livelihood. Therefore, the disadvantages out weigh the advantages because of the long-standing effects.

3)Biological Control

Biological control involves using other species, such as insects, to eliminate or manage the growth of water hyacinth. For example, using plant pathogens and allelopathic plants can help reduce the plant population of water hyacinth.

Table 2: The strengths and weaknesses of biological control to combat water hyacinth.

Biological controls may be the most environmentally conscious solution. However, it might not effectively reduce all water hyacinth when used alone. As such, it should be used before mechanical or chemical treatments, as that supplement would help eradicate the majority of this weed.

4)Using biochar to control the spread of water hyacinth

Intensive control can also be an effective solution. This consists of making biochar from water hyacinth that can be used to enhance soil fertility. Biochar is a sustainable weed that is important for the carbon storage in the soil. The conversion of water hyacinth to biochar is not only environmentally friendly, but also beneficial for soil fertility and quality.

Since water hyacinth spreads extremely fast, it can help increase the energy and carbon potential in these soils. While there are more advantages than disadvantages to this technique, the most constraining factor might be the fear of water hyacinth potentially spreading to yet another water base if it is close to one. This can lead to the water hyacinth growing more rapidly to then close several drainage systems. However, it might be the most sustainable in the future in terms of effectively disposing the water hyacinth from Lake Tana to somewhere useful.

Conclusion:

There are several solutions to combat the spread of water hyacinth in Lake Tana; however, from the analysis above, it is clear that these solutions come with their own strengths and weaknesses. Hence, it is best to use a combination of these strategies.

How to help?

It’s easy. You can:

Donate to the workers who are currently physically removing the plants. Link to donations: gf.me/u/yi2uap
Raise awareness of the issue by sharing this article on your social media or to family and friends.
Share a youtube video on this topic. Link to youtube video: https://youtu.be/9rfKYN7_1b4
Educate yourself on this topic. Below is a list of sources to check out to help understand the issue better.

Sources

https://www.lakerestoration.com/p-159-cattail-and-waterlily-control.aspx

https://doi.org/10.1016/B978-1-4832-8438-5.50062-5

http://dx.doi.org/10.26814/cps2019021

https://cpsjournal.org/2019/12/04/cps2019021/

https://doi.org/10.1080/09670878809371254

https://doi.org/10.1016/0167-8809(91)90149-R

https://www.invasive.org/biocontrol/4WaterHyacinth.cfm

https://doi.org/10.1016/j.catena.2013.06.025

https://doi.org/10.2112/SI86-033.1

http://www.sapub.org/global/showpaperpdf.aspx?doi=10.5923/j.ijaf.20180801.02

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=22839