Effects of channelization on macroinvertebrate assemblages in a small stream: The case of Awetu in Jimma City, Ethiopia

Abstract

Freshwater ecosystems are increasingly modified worldwide by anthropogenic activities. Land use change is one of the leading factors responsible for stream ecosystem degradation. Physical habitat disturbance due to channelization is among the factors responsible for the loss of biodiversity and degradation of river water quality worldwide. Since 2020, Jimma City municipality has been beautifying the city and one of the activities is channelizing using concrete embankment, a part of the Awetu stream that runs through the city. The main aim of this study is to assess the effect of channelization on macroinvertebrate assemblages and the water quality of the Awetu stream. A cross-sectional study was conducted in April 2022. Macroinvertebrates, water samples, and habitat data were collected from 21 sampling sites along the three segments of the stream (upstream, channelized, and downstream). Data were analyzed for different macroinvertebrate metrics and water quality parameters. Canonical Correspondence Analysis was used to examine the overall relationship between macroinvertebrate assemblages and water quality parameters. The upstream site has better macroinvertebrate assemblages than channelized and downstream sites (p < 0.05). The downstream site showed better assemblage compared to the channelized site, though it was not significant. Regarding water quality parameters, a significant variation was observed between channelized and, un-channelized sites (upstream and downstream) (p < 0.05). The habitat condition score varied from 47 (poor) at channelization to 150 (suboptimal) upstream. Upstream sites were found to have relatively better macroinvertebrate assemblages, better water quality, and good habitat conditions. The downstream sites had lower macroinvertebrate assemblages, poor habitat conditions, and degraded water quality compared to the upstream sites. The channelized segment had the poorest habitat, with poor macroinvertebrate assemblages and water quality. Thus, the conservation of habitat conditions along the channelized segments of the Awetu stream is recommended to improve the water quality and macroinvertebrate assemblage.

Keywords: Channelization; Habitat condition; Macroinvertebrates; Urban stream; Water quality.

Fig. 1

Map of the study area with sampling sites along the segments of Awetu stream in Jimma City, April 2022.

Fig. 2

Boxplots show the water quality parameters; a) total hardness, b) EC, c) turbidity, d) temperature, e) DO, f) PO₄³⁻ g) chloride, h) BOD₅, i) pH and j) TSS along the different stream segments of the Awetu stream, April 2022.

Fig. 2

Boxplots show the water quality parameters; a) total hardness, b) EC, c) turbidity, d) temperature, e) DO, f) PO₄³⁻ g) chloride, h) BOD₅, i) pH and j) TSS along the different stream segments of the Awetu stream, April 2022.

Fig. 3

Mean and standard deviation (SD) of habitat conditions assessment score along the different stream segments of the Awetu stream, April 2022.

Fig. 4

Canonical correspondence analysis (CCA) of macroinvertebrate taxa and environmental variables based on the first and second axis along the Awetu stream, April 2022.