Impacts of Land Use and Land Cover Types on Water Quality and Benthic Macroinvertebrates in Great Akaki River Catchment
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Date
2024-06
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Addis Ababa University
Abstract
Limited access to clean water, exacerbated by urbanization, industrialization, and agricultural practices, brings significant challenges to human and ecosystem health. A decline in surface water quality is linked to land use/land cover changes worldwide, necessitating the use of such bio-indicators as macroinvertebrates for biomonitoring. However, efforts made to detect and understand land cover/land use changes and link them to changes in water quality parameters and macroinvertebrate communities structure are limited in Great Akaki River. As to address this limitation, this study aimed to assess the impact of land use land cover changes in the Great Akaki River catchment on water quality and macroinvertebrate community structures. This study was conducted in June and November 2023 at six sampling sites. Temperature, pH, dissolved oxygen, electrical conductivity, total dissolved solids, and turbidity were measured in-situ, while nutrients were analyzed in the Laboratory. Macroinvertebrates were collected from 4 representative biotopes using a square frame hand net and identified to family level. Habitat quality assessment was conducted using the Rapid Bioassessment Protocol. River water quality was classified using SASS 5 and ETHbios methods. Land use land cover was assessed using GIS tools for the years 2008, 2016, 2023. Considering the fact that data were not normally distributed, non-parametric tests, Kruskall-Wallis and Mann-Whitney U tests, were used to assess spatial and temporal variation of water quality parameters, respectively. SPSS and XLSTAT were used for data analysis and filling missing data values, respectively. Principal component analysis was conducted to explore the relationship between land use types and water quality parameters and Redundancy analysis was used to evaluate the relationship between water quality and macroinvertebrates community structure. ANOSIM and SIMPER were used to assess the influence of land use type on macroinvertebrates. Results of the study showed that the main land use types in the catchment area were agriculture, urban land, bare land, vegetation and water body. Agricultural land was the dominant LULC types covering approximately 61.37% in 2008, 60.68% in 2016, and 41.78% in 2023. The analysis of land use change between 2008 and 2023 showed a significant rise in urban area (29.91%), while other land use types decreased. Urban area was strongly and positively correlated with SRP, pH, temperature and TDS indicating the deterioration of water quality with the expansion of urbanization. Agriculture was strongly and positively correlated with SRP while Bare land was strongly and positively correlated with EC and TDS. Examination of the influence of different land use types on macroinvertebrates assemblages revealed that urban area had the highest impact and Order Ephemeroptera contributed the highest variability between land use types. Analysis of water quality-macroinvertebrates relationship revealed positive correlation between several sensitive and moderately sensitive macroinvertebrates families with DO and habitat assessment. The downstream study sites that demonstrated severe ecological impairment since highly tolerant taxa were abundant and had strong correlations with TDS, SRP; and TP, NO3, turbidity levels. The results of the present study will provide valuable information for environmentalists and policy makers in their endeavours directed to sustainable river management.
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Keywords
Akaki River, Benthic Macroinvertebrates, Bioindicator, Land Use/Land Cover, Water Quality