In the last two decades, the negative impact of human activities on the environment has reared its ugly face in most parts of the world. Ethiopia’s Central Rift Valley lakes have not been spared either. Three inter-connected lakes in particular – Ziway, Abijata and Shalla – have perhaps bore the heaviest brunt.
These lakes form part of the seven Ethiopian Rift Valley lakes, the northernmost of the African Rift Valley Lakes system that extends from the Afar depression southwards to the Turkana depression on the Kenyan border. Located on the expanse savannah region about 200 kilometres south of Addis Ababa, the Ziway-Abijata-Shalla sub-basin is critical for the survival of the local communities and migratory birds.
Local communities use Ziway’s freshwaters for domestic use and to irrigate their smallholding farms mainly for food and to boost incomes, where possible. Other large water abstractors are foreign-owned commercial farms. These human activities have reduced water flow from Ziway to Abijata via River Bulbula posing a serious threat to the natural water system of the sub-basin.
Further, Abijata has been receding at an alarming rate due to direct abstraction of its waters for a soda ash extraction plant. In the 1980s, this alkaline lake with no outlet was more than 200 square kilometres; today it is less than half of that. Together with Shalla, the two were established as a national park in 1963 to conserve aquatic birds. With an area of 887 square kilometres, of which 482 square kilometres is the lake ecosystem while the remaining is terrestrial, Lake Abijata-Shalla National Park provides food and habitat for 108 migratory water bird species and hosts 91% of those that migrate through Ethiopia. The pink-plumed lesser flamingos feed on the blue-green algae found in Abijata. But as the lake shrinks, it becomes more saline, poisoning the algae. Inevitably, flamingo populations have diminished.
Other human threats such as livestock grazing, cutting trees for wood fuel and charcoal, and sand harvesting have also contributed to the Park and surrounding area’s degradation and water level reduction of Abijata in particular.