Oral Presentation World Lake Conference 2025

Development of a water hyacinth management system in Lake Tana, head waters of the Blue Nile, Ethiopia (#47)

Kanako Ishikawa 1 , Ji Cai 1 , Chunmeng Jiao 1 , Yoichiro Sakai 1 , Mulatie Mekonon 2 , Solomon Addisu 3 , Hiroki Imamura 3 , Diego Alberto 3 , Victor S Kuwahara 2 , Getachew Bayable 3 , Ashenafi R Milashu 3 , Shinjiro Sato 4 , Mezgebu Dagnaw 4 , Ayalew Wondie 4
  1. Lake Biwa Environmental Research Institute, Otsu, SHIGA, Japan
  2. Bahir Dar University, Bahir Dar, Amhara, Ethiopia
  3. Soka University, Hachioji, Tokyo, Japan
  4. Lake Tana and Other Water Bodies Protection and Development Agency, Bahir Dar, Amhara, Ethiopia

Introduction

The excessive spread of aquatic vegetation is a global issue affecting many lakes, and Lake Tana, the largest freshwater lake in Ethiopia and the headwaters of the Blue Nile, is no exception. Covering approximately 3,000 km² with a maximum depth of 15 meters, the lake has been experiencing accelerated eutrophication due to deforestation-induced soil runoff and increasing domestic wastewater. Since its invasion in 2011, water hyacinth (Eichhornia crassipes) has rapidly expanded, covering over 25 km² by the end of 2020 and affecting one-third of the shoreline. This has severely impacted agriculture, fisheries, and biodiversity conservation.
Despite efforts using harvester boats and manual removal, the absence of systematic management, inadequate planning, and uncoordinated responses have proven insufficient to address the issue effectively.

Development of the Lake Tana Water Hyacinth Management System

To control the excessive proliferation of water hyacinth, our project is developing the Lake Tana Water Hyacinth Management System. This initiative integrates local communities and government agencies in coordinated management efforts. The system leverages ICT and AI technologies to monitor and map hyacinth distribution (Figure 1-①②), establish a web-based platform for environmental data collection (Figure 1-③④⑤), and predict growth trends (Figure 1-⑥⑦). These data will enable authorities to devise strategic removal plans that minimize ecological impact (Figure 1-⑧) while allowing communities to carry out efficient harvesting and resource utilization (Figure 1-⑨).

Key Findings
Due to local conflicts, field investigations have become unsafe, making satellite observations crucial. Long-term satellite data analysis indicates that Lake Tana’s water hyacinth coverage follows a logistic growth curve and has already reached its environmental carrying capacity. Seasonal variations show expansion during the rainy season and reduction in the dry season. Furthermore, analysis of meteorological and environmental factors confirms that water level fluctuations significantly influence hyacinth expansion.

Lake Tana’s water management is a politically sensitive issue for downstream nations such as Sudan and Egypt. The Grand Ethiopian Renaissance Dam (GERD), under construction since 2011, began reservoir filling in 2020 and is now generating power. For local governments and communities managing Lake Tana’s ecosystem, real-time monitoring and data-driven decision-making will be increasingly important for sustainable management.

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