Abstract:
This research is mainly concerned with determining the effects of changes in land cover
on stream flow and determining the extreme flows. Using the watershed region, QGIS
was used to build and extract land use and cover maps in 1995, 2005, 2015, and 2020.
Four QSWAT models were set up and ran using the four generated land cover maps to
examine the impacts of land use and land cover changes on the stream flow of the study
watershed. The SWAT cup software's performance has been evaluated through sensitivity
analysis, calibration, and validation. Eleven (11) flow characteristics were found to be
responsive to the research area's stream flow and were utilized to calibrate the model.
The model was calibrated using observed stream flow data from January 1, 1995 to
December 31, 2014, as well as a validation period from January 1, 2015 to May 29,
2020. Both the calibration and validation results showed a good agreement between
measured and simulated flows. During calibration, R
2
and Nash-Sutcliff efficiency were
0.65 and 0.64, respectively. While, during validation R
2
and Nash-Sutcliff efficiency, NSE
were 0.62 and 0.60, respectively. Generally, the average daily extreme high flow declined
from year to year, while the extreme low flow shows irregularities. The study revealed
that cultivated land has increased during the study period of 1995-2010 and beyond. In
recent years from 2010 to date, reforestation was observed.
Key words: LULC change, QSWAT, Stream flow, regionalization, parameters