bantwale diress

Droughts are common natural phenomenon in Ethiopia which has been affecting food insecurity and imposing other complex problems. Severe droughts happened once every 10 years in the north and north east Ethiopia, now becoming more frequent and covering areas that never experience drought before, in the southern parts of the country. According to IPCC droughts will become more intense, frequent and severe in the future due to the impact of climate change. This thesis presents the assessment of projected impact of climate change on hydrological drought in the Lake Tana basin in Ethiopia, which is the headwater for the Blue Nile River. The rainfall-runoff HBV model was calibrated and validated against historical data to obtain a reference situation to the possible impact of climate change on hydrological drought in four sub-basins and the Lake Tana basin. Datasets obtained from the EU- ATCH project for three General Circulation Models (CNCM3, IPSL and ECHAM) were used as an input to the HBV model, which was recalibrated for the same historic period to obtain an assessment to what local downscaled, bias-corrected GCM can be used as a forcing data for hydrological drought assessment. Next the GCM outputs with the recalibrated HBV model were usedto simulate future streamflow for two future time windows (2021-2050 and 2071-2100) and for one future emission scenario A2. The variable threshold level method combined with a 10-day moving average streamflow was used to detect hydrological drought characteristics.

According to IPCC (2007) developing countries like Ethiopia are more vulnerable to adverse impacts of climate change and variability due to their low adaptive capacity.  Agriculture accounts for nearly half of the country’s GDP, more than 80 percent of its export revenues, and roughly 85 percent of employment. The agriculture sector is mainly depend on rain feed agriculture which is highly sensitive to climate change and variability. Pastoralists and agro-pastoralist account about 13% of the total population. Climate change has direct effects on livestock productivity as well as indirectly through changes on the availability of fodder and pastures. According to IPCC (2007) developing countries like Ethiopia are more vulnerable to adverse impacts of climate change and variability due to their low adaptive capacity.  Agriculture accounts for nearly half of the country’s GDP, more than 80 percent of its export revenues, and roughly 85 percent of employment. The agriculture sector is mainly depend on rain feed agriculture which is highly sensitive to climate change and variability. Pastoralists and agro-pastoralist account about 13% of the total population. Climate change has direct effects on livestock productivity as well as indirectly through changes on the availability of fodder and pastures. A Statistical downscaling model was developed and validated using large-scale predictor variables derived from the National Centre for Environmental Prediction (NCEP) reanalysis data and observed station data that was achieved in order to establish a statistical relationship between large-scale NCEP reanalysis predictor variables and locally observed meteorological variables. The relationship obtained was then used to generate the possible future scenarios of meteorological variables such as temperature and precipitation using large-scale predictor variables obtained from the Global Climate Model, HadCM3 (Hadley Centre Coupled Model version3) outputs for A2 and B2 emission scenario. The downscaling was done for intermediate (2021-2050) and far future (2070-2099) periods. The validation results of the SDSM revealed a good agreement between simulated and observed values for temperate. But the model underestimates simulated precipitation. The impact assessment over the South Omo projects an increase in precipitation in both periods. Both the minimum and maximum temperature are projected to increase in a range of 0.5 0 C to 1.20 C for both intermediate and far future periods. For future period the potential evapotranspiration could also increase due to the rise of temperature that leads to more severe drought.  Enclosed range land management was proposed by study for climate change adaptation, for this a capacity building training was given for the pastoralist community on range land management. Developmental activities by the government on that part of the area could be a treat and an opportunity for the pastoralist community for adaptation of climate change.


Keywords: Climate change, SDSM, South Omo

This study used MM5 meso-scale modelling to analyse the influence of regional atmospheric circulation on flooding of the Ethiopian highlands from 26th-28th of July 2006. It had been found that the northern, south western and the central highlands of the country had showed large amount of precipitation and cloud cover in comparison to the lowland parts of the country, in the East and South east, due to the effect of topography and regional weather systems. Investigating the effect of topography on precipitation reveals that there was a clear reduction in the amount of precipitation and a shift in the pattern of precipitation, when topography height was reduced by 50%. While topography had increased by 50%, no clear pattern of precipitation had been revealed.  In general topography and regional weather systems play a great role in the amount and spatial pattern of precipitation in the region.
Key words: MM5, topography, Ethiopia, precipitation, cloud cover