Author(s): Ahmadul Hassan; Sameh A. Kantoush
Linked Author(s):
Keywords: SWAT model; Cascade dams on the Blue Nile; Renaissance dam in Ethiopia; Climate change; Hydrological modeling
Abstract: The present paper aims to develop an operational water balance model (based on an analysis of rainfall-runoff and basin characteristics) and schematics for each basin/subbasin of the Eastern Nile indicating the basic water balance (including diversions, losses, etc. ) from best available information and providing hydrologic inputs for the Eastern Nile Planning Model. The specific objectives of the paper are: To improve understanding on the hydrology and hydrological complexity and variability with respect to spatial and temporal aspects in the whole Eastern Nile Basin (ENB); To schematize and set up an operational (calibrated and validated) water balance model for the four sub -basins of the ENB; To develop and generate exogenous scenarios (climate change, draught) and endogenous scenarios (water management, infrastructure: dam, irrigation schemes) for the planning model. To achieve these three objectives a three-step methodology has been developed. The first step is to review and analyze relevant available documents, studies and databases to understand the hydrological complexity of the ENB. The Soil and Water Assessment Tool (SWAT), which is a semi distributed hydrological model, has been selected to be applied in the ENB. SWAT is simple, flexible and robust enough to be applied in a large basin like the ENB. In scenario analysis, a total of 20 scenarios have been developed and simulated and compared with the long term base scenario. In these 20 scenarios eight exogenous, three endogenous and nine combined scenarios have been simulated. The exogenous scenarios include two drought scenarios (Ex01: Drought: Repeat 1979 to 1984 hydrological condition and Ex02: Drought: Repeat 1984 condition for 3 years), two climate change scenarios (Ex 03: Climate change: A2 Emission scenario with 80 percentile ensemble 18 GCM results and Ex 04: Climate change: A2 Emission scenario with 20 percentile ensemble 18 GCM results) and a combination of drought and climate change. The endogenous scenarios include dam scenario, irrigation scenario, land use change scenario and sediment management scenarios. In the dam scenario four dams (Renaissance, Beko Abo, Karadobi and Mandaya) are included in the Abay-Blue Nile sub-basin. Land use change scenario and sediment management scenarios are not included in the present study. In this paper a conceptual climate change adaptation framework has been developed to see how it could work in the future. For example, an adaptation strategy could be the establishment of water reservoirs. Renaissance dam in Ethiopia construction could increase the water flow during dry season and decrease the flow in monsoon in a way that will minimize water shortage as well as increase water accessibility throughout the year and reduce risk from flooding.
Year: 2013