EXAMINING THE INFLUENCE OF LAND USE AND LAND COVER ON RIVER MORPHOLOGY: CASE OF LIKANGALA RIVER, ZOMBA, MALAWI

In the face of escalating environmental challenges, the changes in land use and land cover emerges as a persistent threat, profoundly impacting the stability of natural water systems. This study investigates the influence of land use and land cover (LULC) changes on river morphology, with a particular focus on the effects of urbanization, agriculture, and deforestation. Utilizing satellite imagery for years 1993, 2002, 2013 and 2022, GIS tools and Google Earth Pro, the research examines how different land uses impact river characteristics such as width, length, and sinuosity. Data were collected from different sources including the Earthexplorer.usgs.gov for Landsat images. LULC maps for the years 1993, 2002, 2013 and 2022 were generated incorporating the spectral indicators such as vegetation, water, built up area, bare land and barren land. The findings revealed that built up land from 1993 to 2022 underwent the most significant changes by increasing from 10.87km2 to 36.02km2 representing 69.82% followed by bare land which changed from 77.71 km2 to 109.81km2 representing 29.23% while vegetation decreased by 30.07 km2. Water on the other hand changed from 5.33 km2 to 5.86km2. The study also employed the analysis of hydro-meteorological data which was obtained from DCCMS and Ministry of Water and Sanitation in the water resources department for rainfall and streamflow data respectively. The results revealed a decreasing trend in both rainfall and streamflow. The river morphology changed as well with average length changing from 20.96 km to 10.56 km, sinuosity decreased from 1.87 to 1.5. The substantial correlations between LULC changes and alterations in river morphology were done. Specifically, urbanization and deforestation as a result of built up and bare land increase to the expense of vegetation, are linked to increased sedimentation and reduced river width, while rainfall revealed a strong relationship with rainfall contributing to significant changes in river sinuosity. These results underscore the importance of sustainable land management practices that consider the impacts on river characteristics and its ecosystems.

Utilizing satellite imagery for years 1993, 2002, 2013 and 2022, GIS tools and Google Earth Pro, the research examines how different land uses impact river characteristics such as width, length, and sinuosity. The findings revealed that built up land from 1993 to 2022 underwent the most significant changes by increasing from 10.87km2 to 36.02km2 representing 69.82% followed by bare land which changed from 77.71 km2 to 109.81km2 representing 29.23% while vegetation decreased by 30.07 km2. The study also employed the analysis of hydro-meteorological data which was obtained from DCCMS and Ministry of Water and Sanitation in the water resources department for rainfall and streamflow data respectively. Specifically, urbanization and deforestation as a result of built up and bare land increase to the expense of vegetation, are linked to increased sedimentation and reduced river width, while rainfall revealed a strong relationship with rainfall contributing to significant changes in river sinuosity.

The Likangala River, 15°22′-15°30′ S, 35°15′-35°37′ E, at 631 m to 1 603 m above sea level and with a catchment area of 756 km is about 50 km long (Chidya et al. 2011). The Likangala catchment is affected by increasing population which has resulted in urban sprawl with many new settlements in Zomba city and Thondwe town, the two major urban areas in Zomba District (Pullanikkatil, Palamuleni, & Ruhiiga, 2016). The according to (Pullanikkatil, Palamuleni, & Ruhiiga, 2016), Likangala catchment is 756 km2. And has several rivers including Mulunguzi which forms its sub catchments. However, this study combined sub catchents for rivers that flow through the city and empty its water into Likangala before Mkokangowo gauging site. The area of this sub catchment is found to be 232.15km2. The river is perennial, with a large difference in water discharge over the year, with a peak in wet season, which normally occurs around November until April. The rainfall distribution is fairly uniform and the climate is a tropical wet and dry or dry savanna. The study area contains a variety of land uses which include forest, residential, commercial and agriculture areas. Increased human activity has attributed to 6.59% population growth rate of Zomba city annually, which led to the population growing from 65,915 to 116,797 between 1998 and 2022 alone (National Statistical Office, 2023; Strachan et al., 2021, (UNIMA, 2024)

Traditional authority: TA Mwambo

District: Zomba

Coordinates: -15.4653, 35.5092