Water quality assessment of Ashmaq and Sawur streams using physicochemical and biological indicators, Kewote district, Central Ethiopia

Abstract

Abstract Tropical streams have distinct natural features that are heavily influenced by human activities, especially in developing regions. The impact of human activities is measured by exploring changes to the streams’ natural physicochemical properties and biological communities. However, information on the physicochemical and biological characteristics of smallest streams with great socioeconomical importance remains scarce in Ethiopia. Thus, this study assessed the physicochemical and biological characteristics of Ashmaq and Sawur Streams (Aug 2022–Apr 2023) to evaluate human impacts on stream ecology of the rural areas. The area of this region is generally semi-arid characterized by erratic rainfall patterns where June to August and December to April, are rainy and driest months, respectively. Water and macroinvertebrate samples were taken at two sampling sites of each stream at different water depths using sterilized plastic bottles and a D-frame net, respectively and gillnets and hooks were used to sample fish. Accordingly, a total of 1386 and 149, macroinvertebrates and fish, respectively were sampled. In the laboratory, water samples were analyzed using the American Public Health Association (APHA) standards. ANOVA was employed to show the significant difference in spatio-temporal patterns of stream water physicochemical parameters. In the present study, EC ranged between 187.90 ± 61.60 to 662.00 ± 6.56 µScm -1 , and highest values were recorded during the wet months. Temperature, pH, dissolved oxygen, chloride, and nutrients (NO 2- and PO 4 2- ) were major environmental variables that characterize distribution patterns of fish and macroinvertebrate communities. Almost all the in-situ examined physicochemical parameters revealed spatio-temporal significant differences in both streams. Corixidae was the dominant family of macroinvertebrates, while Labeobarbus intermedius accounted for 67.4% of the total collection of fishes identified. In conclusion, most physicochemical features of Ashmaq and Sawur streams were below the permissible limits set by international standards. However, our personal observation encountered that Ashmaq and Sawur streams are facing several ecological threats including poor agricultural practices, water abstraction, intensive grazing, and sand mining. Therefore, this baseline data on the tiny percentage of global freshwater ecosystems could help with management implications like habitat restoration and raising public awareness and educating people about the need to save water and their biodiversity.