Community pulls water-thirsty invasive weeds from Ethiopia’s Lake Tana

Community pulls water-thirsty invasive weeds from Ethiopia’s Lake Tana


  • Lake Tana is Ethiopia’s largest lake, and feeds the Blue Nile.
  • At several points where tributaries flow into the lake, invasive water hyacinth is soaking up water and choking the shoreline.
  • A 2012 study found that there were 20,000 hectares of water hyacinth on Lake Tana. In five years, that number doubled.(news.mongabay)—Last week thousands of people in northwest Ethiopia marched to Abay River and Lake Tana as part of the “Save Lake Tana” movement to remove invasive water hyacinth by hand. The free-floating, water-thirsty perennial can grow up to three feet tall and is swallowing the northeast shores of Lake Tana, impacting both aquatic habitat health and local fishermen.

    Lake Tana is the source of the Blue Nile and the largest lake in Ethiopia. The lake is frequently used for transport, tourism, hydroelectric power generation, ecological conservation and fishery operations. It is home to 28 fish species, out of which 16 are endemic.

    A team of university researchers discovered in 2012 that 20,000 hectares of the lake’s body was covered by invasive water hyacinth (Eichhornia Crassipes). Since then, it’s gone to a peak infestation of 40,000 hectares. At first, the hyacinth was mainly found in an area with three tributaries to Lake Tana.

    Farmers march to Abay River to participate in manual removal of the weeds. Maheder Haileselassie Tadese/Mongabay

    Although numerous attempts have been made to eradicate the weed by hand over the last several years, the hyacinth continues to come back. The plant has the ability to spread rapidly 4,000-5,000 seeds each. Each seed can stay dormant for 28-30 years. The local people say the invasive aquatic plant because it just keeps coming back, no matter how many times they remove it from the water.

    According to the area’s Water Hyacinth Eradication Program Coordinator, 71 hectares of the aquatic invasive plant is found on Abay River and an estimated 24,000 hectares has been measured in several nearby areas just this year.

    Farmers frequently engage in eradication work. In the past five years, manual labor invested in an effort to eradicate the weed is valued at more than $1.5 million.

    People come up with different strategies to remove as many weeds as they can. One of those is to stand in line and push segments of weeds together. Maheder Haileselassie Tadese/Mongabay

    So far, farmers and the fishermen have been the mainstay in the labor intensive removal work, but this year, local authorities report that youth is joining in the movement to save the lake and its tributaries from the plant.

    Among the organizations involved in saving Laka Tana is anew non-profit, Tana and its Environs Protection and Rehabilitation Association. It was established this year by 70 youth from Ethiopia’s capital Addis Ababa, and 21 from another city.

    According to the organization’s president, Kalkidan Tsena, most of the founding members came to know each other on social media, where the idea of coming together was first born. The organization has done two marches to the lake so far and aims to do more than just eradicate the water hyacinth.

    The weeds after they are removed from Abay River and placed nearby before being burned, even though once out of the water, they die. Maheder Haileselassie Tadese/Mongabay

    “Tana is a past, a present and a future for us. It is more than just a water body. It’s a source of joy and a source of identity for us,” said Christian Tadele, temporary director of the Addis Ababa city branch of the association.

    Currently, different solutions are being investigated by Ethiopia’s Environment, Forest and Wildlife Protection and Development Authority to eradicate the pant.

    One measure that has not been looked at in-depth is prevention. Lake Tana basin is known to have high levels of nitrogen and phosphorus that are vital for the existence of water hyacinth. Some experts argue that prevention can start from addressing the source of these nutrients which could possibly be the result of poor waste water management in the area.

    In light of managing established water hyacinths, mechanical and biological methods are being investigated by different institutions and universities. As part of a mechanical control measure, Ethiopia’s Gonder University has been engaged in making a water hyacinth harvesting machine that is expected to become functional soon. At Bahirdar University, they are working on biological solutions involving the mass rearing of weevils to reduce the infestation in a much more effective way.

    As challenging as it is, if successful, authorities plan to eradicate the water hyacinth from the water bodies in the coming calendar year by implementing possible strategies, including a trust fund in the name of the cause.