Impact Assessment of Climate and Land Use Change on Tikur Wuha River

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Addis Ababa University


The Specific objectives of this study are to asses impact of land use and climate change on Tikur Wuha River located at Awassa Lake catchment. Hydrologic model, HEC-HMS model was used to asses’ impact of climate and land use change. Orthorectified Landsat MSS, TM and ETM+ images covering the study area was classified by supervised image classification using maximum likelihood classifier (MLC). The sample set for the classification was created using the combination of bands 7, 4, 2 (for Landsat TM and ETM+ images of year 1986 and 2000, 2005,) and bands 4, 2,1 (for Landsat MSS image of year 1973). Result of image classification showed 28.77% reduction in forest cover, 3.6% reduction in lake cover, 23.49% increase in agricultural land, 3.6% increase in swamp and 5.3% increase in grassland within the span of 32 years from 1973 to 2005. Hydrologic impact assessment indicated that with the land-cover changes that have occurred, there is a change on the catchment runoff. This study reveals that watersheds run off was lower by 5.79 % in period 1973, 0.27% in 1986 compared to period of 2005 as reference. Statistical Down-Scaling Model (SDSM) was used to derive local scale information from global climate scenarios generated by GCMs. Among four scenario families of Special Report on Emissions Scenarios (SRES), three of them (A1B, A2 and B1,) scenarios were used in this study. Historical weather data collected were used to calibrate and validate downscaling models. After calibration and validation, the downscaling model was used for computing future temperature and precipitation pattern. SDSM downscaled future precipitation was used in hydrologic model to asses impact of future climate change. The assessment showed that average mean flow increased in the future periods considered (2015 - 2035, 2040 - 2050 and 2080-2099). SDSM downscaling data resulted increase in the mean annual flow by minimum of 20.05 % and maximum of 51.67 % during time periods considered for three of emission scenarios considered. Impact assessment of land use change showed that the runoff volume of Tikur Wuha River increases over past 32 years. Climate change impact analysis also showed that the river flow would increase in future.



Statistical Down-Scaling Model (SDSM)