Assessing the impact of watershed land use on Kebena river water quality in Addis Ababa, Ethiopia

Abstract

Background The impact of watershed land-use on surface water quality is one of the under researched areas in mega cities of the developing countries like Addis Ababa. The study examined the impact of watershed land uses on the Kebena river water quality within its seasonal and spatial variation and assessed the relationship between river water pollution and dominant land-use types in the sub-watersheds. Method The main land use types in the sub-watersheds were digitized from aerial photograph of 2016, and quantified for water quality impact analysis. Water samples were collected from the main Kebena river and the three sub-watersheds source and outlet points. A total of 128 samples were collected during the dry and wet seasons of 2016 and 2017 and analyzed for various water quality parameters. The study employed ANOVA, independent t-tests and multiple regression analysis to examine variations in water quality and assess the influence of the different land uses on water quality. Results Forest, built-up area and cultivated lands are the three major land use types in the Kebena watershed accounting for 39.14, 32.51 and 27.25% of the total area, respectively. Kebena catchment is drained by three sub-watersheds namely, Denkaka (44.9% cultivated land), Little-Kebena (60.87% forested) and Ginfle (90.44% urban land). The concentration of pollutants in the Kebena river was significantly higher (P < 0.001) in the dry season than in the wet season. However, when compared to surface water quality standards, both the dry and wet season water quality records are exceptionally high. The urban and forest dominated sub-watersheds contribute significantly high amount of (P < 0.001) pollutant loads to the river which is associated with high runoff from impervious surfaces and sewerage discharge to the river from nearby urban settlements. Conclusion Integrating watershed planning with land use planning is of paramount importance to address water quality problems in urban areas. Thus, in the urban dominated sub-catchment, land-use planning should aim to relocating river front communities, providing sufficient river buffer-zones and forwarding appropriate storm water management schemes. In the forested sub-catchment, planning should protect, retain and enhance the existing natural green spaces through open space planning, and management schemes while providing wide river-buffer with natural vegetation cover to minimize pollution load to urban rivers from agriculture dominated sub-watershed.

Analysis of the Effects of Local Regulations on the Preservation of Water Resources Using the CA-Markov Model

“…However, the analysis suggests that the result was mainly affected by the fact that water pollutant loads generated by other types of LULCs had insignificant effects on the changes observed in terms of pollutant loading. As a previous study of water quality change due to LUCC, Kalkidan et al [59] reported a significant contribution to water pollution loads from urban areas and forests for deteriorating water quality. Nafi'Shehab et al [60] analyzed the causes of water quality deterioration in the Bentong River in Malaysia and reported that urban and agricultural areas affect water quality deterioration and forests affect water quality improvement.…”

Integrating river restoration goals with urban planning practices: the case of Kebena river, Addis Ababa

“…Settlements around the river has grown fast in the past few years resulting in a large number of informal settlements developed very close to the river and in the surrounding areas ( AACASPO, 2017 ). The lower catchment of Kebena River is predominantly built-up area, whereby some nearby residents use the polluted river water to irrigate urban vegetable farms ( Asnake et al., 2021 ).…”

“…Kebena river is one of the three major rivers flowing through the city and heavily impacted by rapid urbanization (Beyene et al, 2009). The lack of proper planning and growth regulations has exposed the city's rivers and their buffer zones to informal settlements (Asnake et al, 2021). Similar to the other rivers in Addis Ababa, Kebena river buffers have become de facto dumping sites for urban waste (Seyoum et al 2017).…”

“…The lack of proper planning and growth regulations has exposed the city's rivers and their buffer zones to informal settlements ( Asnake et al., 2021 ). Similar to the other rivers in Addis Ababa, Kebena river buffers have become de facto dumping sites for urban waste ( Seyoum et al.…”

Factors Affecting People’s Environmental Awareness In The Urban Areas: A Case of Addis Ababa, Ethiopia

“…Despite the importance of the topic, empirical studies hardly examined environmental awareness in Addis Ababa. Existing studies focused on the human impact, urban rivers, watershed land use, surface water pollution, and flood vulnerability (Akalu et al, 2011;Asnake et al, 2021;Eriksson and Sigvant, 2019;Mohamed and Worku, 2020). Several studies conducted on solid waste (Beyene and Banerjee, 2011;Destaw et al, 2013;T.…”