117
Other researchers have also linked the floods in the wetland catchments of
Lilongwe to urbanization. Wiyo et al. (2015) argue that anthropogenic activities on
land use have increased surface runoff, triggering a sequence of floods in Lilongwe
urban areas. Indeed, similar patterns have emerged in Likuni and Lingadzi catchments in the same district (Chikankheni 2009). Kambalame (2017) also establishes
that due to land use changes between 1999 and 2004, surface runoff coefficient
increased from 0.03 to 0.20 for Likuni and 0.08 to 0.24 in Lingadzi. This chapter
attempts to establish information on hydrological changes of Njewa wetland, in
order to provide basis for its management in the advent of rapid land use changes,
estimate land cover change, determine streamflow discharge, and estimate baseflow
and surface runoff coefficient.
2 Methodology and Study Area
2.1 Study Area
Malawi is located in Southern Africa and is part of the Southern Africa Development
Community (SADC). The study was conducted in Njewa catchment, located at latitude 13
°
58′28.46’S and longitude 33
°
42′23.77E in Lilongwe District. The catchment area is at an elevation ranging from 1103 m in the wetland to 1134 m at the
highest point. The area receives unimodal rainfall (mean annual rainfall of 980 mm),
with most rains falling between November and March. The land use is characterized
with a wetland now turned into warehouses and buildings constructed on agricultural land. The soil type is loam in the uplands and clay in the wetland (Fig. 1).
2.2 The Method
To establish the relationship between land use change and hydrological processes of
the wetland, geographical information system technologies were applied during
land use-related assessments while hydrological and meteorological analyses were
based on hydrographs analyzed in Microsoft Excel.
The first step in land cover assessment involved delineating the wetland catchment area using topographic maps and digital elevation modeling (DEM). GPS was
used to collect coordinates of the watershed line of the catchment, which were then
used in Quantum GIS version 2.18.20 (https://qgis.org/en/site/forusers/download.
html) to produce maps. The second step of land use assessment involved analyzing
Landsat images (http://www.earthexploerer.com) in ArcGIS version 10.6.
Hydrological parameters such as stage and streamflow discharge were monitored
for a period of 10 months (from July 1, 2017, to April 30, 2018) to cover both rainy
and dry seasons. A control section of 11 meters of the reach to culvert boxes located
A Hydrological Assessment of Wetlands in Lilongwe Peri-urban Areas: A Case…
Other researchers have also linked the floods in the wetland catchments of
Lilongwe to urbanization. Wiyo et al. (2015) argue that anthropogenic activities on
land use have increased surface runoff, triggering a sequence of floods in Lilongwe
urban areas. Indeed, similar patterns have emerged in Likuni and Lingadzi catchments in the same district (Chikankheni 2009). Kambalame (2017) also establishes
that due to land use changes between 1999 and 2004, surface runoff coefficient
increased from 0.03 to 0.20 for Likuni and 0.08 to 0.24 in Lingadzi. This chapter
attempts to establish information on hydrological changes of Njewa wetland, in
order to provide basis for its management in the advent of rapid land use changes,
estimate land cover change, determine streamflow discharge, and estimate baseflow
and surface runoff coefficient.
2 Methodology and Study Area
2.1 Study Area
Malawi is located in Southern Africa and is part of the Southern Africa Development
Community (SADC). The study was conducted in Njewa catchment, located at latitude 13
°
58′28.46’S and longitude 33
°
42′23.77E in Lilongwe District. The catchment area is at an elevation ranging from 1103 m in the wetland to 1134 m at the
highest point. The area receives unimodal rainfall (mean annual rainfall of 980 mm),
with most rains falling between November and March. The land use is characterized
with a wetland now turned into warehouses and buildings constructed on agricultural land. The soil type is loam in the uplands and clay in the wetland (Fig. 1).
2.2 The Method
To establish the relationship between land use change and hydrological processes of
the wetland, geographical information system technologies were applied during
land use-related assessments while hydrological and meteorological analyses were
based on hydrographs analyzed in Microsoft Excel.
The first step in land cover assessment involved delineating the wetland catchment area using topographic maps and digital elevation modeling (DEM). GPS was
used to collect coordinates of the watershed line of the catchment, which were then
used in Quantum GIS version 2.18.20 (https://qgis.org/en/site/forusers/download.
html) to produce maps. The second step of land use assessment involved analyzing
Landsat images (http://www.earthexploerer.com) in ArcGIS version 10.6.
Hydrological parameters such as stage and streamflow discharge were monitored
for a period of 10 months (from July 1, 2017, to April 30, 2018) to cover both rainy
and dry seasons. A control section of 11 meters of the reach to culvert boxes located
A Hydrological Assessment of Wetlands in Lilongwe Peri-urban Areas: A Case…