Impact of Land Use/Cover Change on Soil Erosion and Surface Water Quality: A Case of Upper Lilongwe River Catchment, Central, Malawi.
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Date
2020-07-08
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Addis Ababa University
Abstract
Safe drinking water, hygiene and good sanitation are important for good health, human survival and development. However anthropogenic activities such as land use have affected water quality in many river catchments worldwide. The adverse effect of water pollution has attracted management attention and research interest in both developed and developing countries. However, there is very limited knowledge on the influence of land use and land cover on water quality in Malawi’s catchments. Therefore, this paper aimed at assessing the impact of Land use on Soil erosion and Water quality in upper Lilongwe river which is very important for drinking, irrigation and recreation of Malawi’s capital city. The study first assessed the land use patterns between 1989 and 2019 and results showed that forest land has decreased from 66727 ha to 33594 ha from 1989 to 2019 indicating a forest loss of 46.65%. Grass/shrubs/bare land has also declined by 11.49% and water body by 25.32% within the same period. On the other hand, cultivated land has increased by 26.06% and built up by 56.68%. The land use maps indicate that Lilongwe River catchment has experienced declines in forest land with conversion into shrubs and grasslands then cultivated and built-up. Water bodies such as wetlands have also been converted into cultivated lands. The impact has been water resources depletion and watershed degradation that include accelerated rate of soil erosion and water quality degradation. Soil erosion was assessed by using MUSLE model and revealed that about 83% of the area was classified to not have any soil erosion risk (< 1 ton/ha/yr) and 16 % light risk (1-10 tons/ha/yr). For assessment of water quality, nine water monitoring points across the upper, middle and lower catchment were sampled during the rainy season in February 2020. Turbidity, SS, TDS, EC, nitrates, phosphates, pH and faecal coliform were analysed according to standard methods and compared with MBS drinking water standards. The results showed significant (p>0.05) spatial variability of nitrates, phosphate and faecal coliform between the upper section and the middle and lower section. Furthermore, the study found a positive correlation between cultivated land, Built-up with nitrate and phosphate while forest and grassland had an inverse relationship with nitrate and phosphate. This study suggests that the implementation of integrated watershed management, promoting afforestation, enforcement of buffer zones along the river banks can assist in improving the state of the catchment and improving water quality and quantity within the catchment.
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Catchment, Land Use Napping, MBS, MUSLE