Assessing the Impacts of Land Use and Land Cover Changes on Hydrology of the Mbarali River Sub-Catchment. The Case of Upper Great Ruaha Sub-Basin, Tanzania.
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Date
2018
Journal Title
Journal ISSN
Volume Title
Publisher
Scientific Research Publishing Inc.
Abstract
Intensification of agricultural land use and population growth from
1990-2017 has caused changes in land cover and land use of the Mbarali River
sub-catchment which is located in the Upper Great Ruaha Sub basin, Tanzania. This has affected the magnitude of the surface runoff, total water yield
and the groundwater flow. This study assesses the impacts of the land cover
and land use changes on the stream flows and hydrological water balance
components (surface runoff, water yield, percolation and actual evapotranspiration). The land use and land cover (LULC) maps for three window period
snapshots, 1990, 2006 and 2017 were created from Landsat TM and
OLI_TIRS with the help of QGIS version 2.6. Supervised classification was
used to generate LULC maps using the Maximum Likelihood Algorithm and
Kappa statistics for assessment of accuracy. SWAT was set up and run to simulate stream flows and hydrological water balance components. The assessment of the impacts of land use and land cover changes on stream flows
and hydrological water balance component was performed by comparing hydrological parameters simulated by SWAT using land use scenarios of 2006
and 2017 against the baseline land use scenario of 1990. Accuracy of LULC
classification was good with Kappa statistics ranging between 0.9 and 0.99.
There was a drastic increase in areal coverage of cultivated land, for periods
1990-2006 (5.84%) and 2006-2017 (12.05%) compared to other LULC. During 2006 and 2017 surface runoff increased by 4% and 9% respectively; however, water yield increased by only 0.5% compared to 1990 baseline period.
This was attributed to increased proportion of cultivated land in the sub-catchment which has a high curve number (59.60) that indicates a higher
runoff response and low infiltration rate.
Description
Keywords
Geographic Information System (GIS), Mbarali River Sub-Catchment, Land Use and Cover Change, Soil and Water Assessment Tool (SWAT), Water Balance, Stream Flow