International Journal of Waste Resources

Abstract

Assessing the Impact of Existing and Future Water Demand on Economic and Environmental Aspects (Case Study from Rift Valley Lake Basin: Meki-Ziway Sub Basin), Ethiopia

Abebe Guadie Shumet and Kassa Tadele Mengistu

In the development of water resource projects there is an increase and extensive use of water resources, which causes exploitation of the existing systems and ecosystem of the natural environment. The Water Evaluation and Planning (WEAP) model is used to assess water demand by considering the existing development situation and future water resources development with scenarios analysis in the study area (Ziway Meki Sub Basin, Ethiopia). Three different development scenarios were developed to simulate water use at demand sites. In the simulations, the catchment was divided into 5 main sub-catchments where the supply and demand nodes were spatially located. The competing water sectors were irrigation development, domestic users, soda ash industry and environmental flow requirements. Hydro Meteorological data, net evaporation from Lake Reservoir, and monthly water demand from user sectors were the basic inputs to the model. The results of the reference scenario were validated using observed flows. Accordingly, the simulation result revealed that the total average annual inflow volume into the study area is declining significantly for reference scenarios and water availability is limited in the months of January (17 Mm3) and December (171 Mm3) while in the other months the availability is efficient and all users have 100% coverage. Except Langano irrigation site that have between 33.33% to 86.5% coverage in average during the month of Feb to May (2.57 Mm3) and April in Bulbula 95.2% coverage, others get full coverage. The minimum reliability observed mostly in the ongoing and likely future development scenarios at Bulbula irrigation demand sites which have 92.11% and 66.67% reliability in Langano irrigation demand sites throughout all development scenarios. On the other hand, in Sher-Ethiopia expansion, 51.75% reliability is observed in ongoing and likely future development scenarios and in demand site of Katar irrigation diversion and Meki irrigation from dam 51.75% is observed in likely future development scenarios.