Abstract:
Land use land cover change is an important landscape process capable of altering the fluxes of water,
sediment, contaminants and energy. SWAT model was used to assess the impact of the Land use
land cover changes on the stream flow and sediment yield of the Gojeb watershed, which is located
in the Omo gibe basin. The land use land cover change analyses were performed using erdas imagine
2014 which was used for further analysis of SWAT. Land use land cover changes for three different
years of 1989, 2000 and 2013 land use was used in different time series for estimation of stream
flow and sediment yield. During the study period most parts of the Forest land were changed to
cultivated land. An increase of cultivated land by 14.97% over 30 years period (1985 – 2015)
resulted an increase of stream flow and sediment yield by 8.6 m3
/s and 41.07ton/km2
respectively.
The Nash sutcliff efficiency(NSE), coefficient of determination (R2) and precent of bias(PBIAS)
were used for evaluating the model performance. The model results has showed a good agreement
with the observed data with NSE > 0.75, R2 > 0.78, and PBIAS < 0.5 values. Spatial variability of
sediment done using the validated sediment yield results of 2013 land use showed high potential
source areas were found at middle and downstream. Hence, for the critical sub- watersheds the
design and development of best management practices were performed. Three BMPs (best sediment
management scenarios) S1 (filter strip), S2 (terrace/ bund) and S3 (reforestation) were considered in
this study. The results has showed a decrease of sedimentation by 22.9%, 29.4% and 32.3% sediment
yield reductions implementing S1, S2 and S3 respectively. Therefore practicing BMP for Gojeb
watershed should be developed and encouraged for efficient sediment reductions.
