Impact of Land Use Land Cover Change on Hydrology of Borkena Watershed, Ethiopia
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Date
2019-10
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Addis Ababa University
Abstract
Land use and land cover change (LULCC) has been a key research priority throughout the world
with multi-directional impacts on both human and natural systems. The objective of this study is
to assess the effect of land use land cover change on stream flow of Borkena watershed. The
study was examined by Arc GIS10.3. SWAT model used with GIS to assess the impact of land
use and land cover change on stream flow. Specifically, the study analyzed the temporal changes
of land use land cover change using 1986, 2000 and 2011 land use and land cover maps. The
model was set up using readily available temporal data, and calibrated using the measured
discharge. Land cover change analysis shown that the cultivated land increased from 8.58% to
14.25%,agricultural land increased from 9.88% to 34.82% as well as urban areas from 1.16% to
9.94% between 1986 and 2011. While shrub land decreased from 11.04% to 8.39%, Forest
decreased from 57.33% to 23.77%, grassland decreased from 10.74% to 8.74%, wetland
decreased from1.26% to 0.09% between 1986 and 2011.CN2, ALPHA_BF, CH_K2 and SOL_Z
were the most sensitive parameters identified for the stream flow of the study area and used for
calibration of the model. The model calibration was carried out using observed stream flow data
from 01 January 1998 to 31 December 2001 and a validation period from 01 January 2002 to 31
December 2003. Both the calibration and validation results showed a good agreement between
measured and simulated stream flow with the coefficient of determination (R
) of 0.93 and NashSutcliffe
efficiency
(ENS) of 0.89 for the calibration, and R
2
of 0.98 and ENS of 0.95 for the
validation periods. Within the calibration and validation period the rainfall and surface runoff
pattern is the same with percentage of fit 90%. Evaluation of SWAT model showed that, annual
surface runoff for land use land cover period of 1986, 2000, and 2011 is 152.37mm, 193.44mm
and 198.8mm respectively. Therefore annual surface runoff increased by +46.43mm and ground
water flow declined by -31.97mm between 1986 and 2011.Therfore, the model results showed
that the stream flow characteristics changed due to the land use/cover changes during the study
periods. This study plays a role to build the ability of planners, researchers and other stake
holders to formulate and implement sound policies to minimize undesirable land use and land
cover impacts on stream flow.
2
Description
Keywords
Stream flow, SWAT model, Land Use land cover change, Borkena watershed