Abstract
The available water volume of Lake Ziway in Ethiopia is declining at an alarming rate which hinders the lake services for a wide variety of sectors. However, there is a lack of systematic study to evaluate the contribution of water withdrawal by various sectors to the decline in the lake actual storage. In the present study, we conducted a Water Abstraction Survey (WAS) to estimate actual water withdrawal from the lake and a water balance model to evaluate the isolated impact of water withdrawal on the lake water volume and level. The likely impact of three development pathways on the lake storage and water level was assessed. Results indicate that the existing water withdrawal for irrigation has significantly contributed to the change in the actual storage of Lake Ziway. When the future development plans are fully implemented, the annual amount of irrigation water withdrawal from the lake will be 94 Mm3. This will cause the lake water level to drop by 0.94 m, which translates to 38 km2 reduction in the lake surface area. Consequently, the lake will lose 26% of its actual storage volume. Hence, the current impact of water resources development around the lake is substantially large and will exacerbate in the future. This calls serious action on the management of water abstraction from the lake.
Highlights
Lake Ziway provides a wide variety of ecosystem services with significant contributions in the livelihoods of many people in the area
We evaluated the actual water withdrawal from the lake and its impact on the water level using a water balance modelling approach
The study was unique as we applied field water abstraction survey coupling calibrated hydrological model output and water balance model
Summary
Lake Ziway provides a wide variety of ecosystem services with significant contributions in the livelihoods of many people in the area. Recent expansion of intensive water abstraction activities from the lake are leading water level drops. This will damage the hydrological and ecological integrity of the lake [1]. Seyoum et al [2] showed that water level of Lake Abiyata significantly changed as a result of human activities. They reported 70% (4.5 m) reduction in lake height between 1985 and 2006. Jansen et al [1] indicated annual average water level of Lake Ziway approximately decreased by 0.5 m as a result of recent expansion of irrigation activities around the lake and its tributaries.
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