Abstract:
Lake Ziway in Ethiopia is a fresh water lake supporting multitude uses, including irrigation,
f
ishing, water supply and recreation. However, the lake is being degraded primarily because
of various land- and water-use activities in its watershed. The purpose of this study is to
evaluate the impact of irrigation water use and evaporation on the water level of Lake
Ziway. This study was estimated the irrigation water requirements of five major crops using
a Cropwat 8.0 model. The annual water balance of Lake Ziway was determined from inflow
components (Rainfall, Katar and Meki rivers and runoff from un-gauged watersheds) and
outflow components (Evaporation, Bulbula river and water abstraction from the lake).
Evaporation loss from Lake Ziway was estimated by Penman method. The water
abstraction for irrigation from the lake was estimated from both existing and potential
irrigable land. The total mean annual inflow from rainfall and surface runoff into the Lake
was estimated 1,107.17Mm3 and outflow from the lake due to evaporation and abstraction
was estimated about 1,212.6 Mm3. Evaporation from the lake was the main component
which affects the Lake Ziway water balance which covers about 30.8% of the total water
balance of the lake. Water abstraction for irrigation use was the second main water losses
that affects the water level of Lake Ziway and it covers14.1% of initial volume of Lake
Ziway and it reduces 0.6m water level of the lake annually. There is a lack of sustainable
utilization and protection of the lake. So, it is recommended to look a solution for
minimization of the amount of outflow components (over utilization of water from this
lake) for its future sustainability. The lake and developments on the lake should implement
water sustainable adaptation measures like low volume irrigation methods, developed a
number of hand dug well, recycling of the used waters like on floriculture.
