A Hydrological Assessment of Wetlands in Lilongwe Peri-urban Areas: A Case of Njewa Catchment, Lilongwe, Malawi
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Assessment of wetlands and evaluation of related anthropic factors are crucial to monitoring impacts of land use changes on hydrological processes. The objective of this research was to assess the hydrological changes of Njewa wetland as it transforms from virgin wetland to industrial settlement. ArcGIS 10.6 was used to analyze the changes in land cover. Global positioning system (GPS) was used to collect geospatial data. Geographic information system (GIS) technologies such as digital elevation model (DEM) were used to delineate the wetland catchment area and produce maps. Velocity-area method was used to monitor streamflow discharge for 10 months, resulting in a seasonal hydrograph. Velocity was estimated using flotation method. The hydrograph was used to estimate baseflow (BF) and surface runoff volume, depth, and coefficient.
The land cover changes indicate that Njewa wetland has transformed from a virgin vegetative cover and farm land into a peri-urban center with lots of industrial buildings. Consequently, surface runoff coefficient has increased from 0.24 to 0.65, and the river flow was characterized with a low baseflow (close to zero). These results underscore that land use changes lead to changes in hydrology of rivers in Njewa wetland, leading to flooding in urban areas.
KeywordsWetland Streamflow discharge Land use Runoff coefficient Catchment Hydrograph
Grateful acknowledgment is made to the Environmental Science and Management Department at LUANAR for the partial funding of this research.
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