Author(s)

DEMELASH WONDIMAGEGNEHU GOSHIME, RAFIK ABSI, BÉATRICE LEDÉSERT, FLORENCE DUFOUR, ALEMSEGED TAMIRU HAILE

Abstract

Significant change has been observed in the water level of Lake Ziway in Ethiopia which hinders its services for a wide variety of ecosystems. However, the contribution of water withdrawal and its impact on the lake water level variation has not been quantified yet. In this study, we conducted a water abstraction survey (WAS) to estimate actual water withdrawal from the lake. Then, we applied a water balance model coupling with simulated river inflow from rainfall-runoff model output data to evaluate the isolated impact of water withdrawal on the lake water level from 1986–2000 at monthly time steps. The amount of water withdrawal from the lake for irrigation water use is 37 × 10⁶ m³ per year. This led to 0.36 m drop in the lake level which corresponded to 18 km2 reductions in the lake surface area. This consequently resulted in a reduction of mean annual lake volume by 162 × 10⁶ m³ from 1986–2000, which accounts for 23% of the total lake inflow from rivers.The results indicate that abstraction from the lake is a significant contributor to the drop in water level of Lake Ziway. This calls for serious action on the management of water abstraction from the lake.

Keywords

Lake Ziway, water level, irrigation water abstraction, impact, surface area.