Water and habitat quality assessment in the Honi and Naro Moru rivers, Kenya, using benthic macroinvertebrate assemblages and qualitative habitat scores

摘要

An assessment of water and habitat quality, based on macroinvertebrate assemblage indices and qualitative habitat scores (QHS), was undertaken in the Honi and Naro Moru rivers, Kenya, in 2011. The two rivers are important as water sources for the local communities and as habitat for organisms such as invertebrates in the national parks there. The Naro Moru upstream site (QHS: 83%) is unmodified, with minimal human influence. The Honi downstream site and the Naro Moru midstream and downstream sites experienced moderate to large modifications in habitat and biota (QHS: 40-80%). South African scoring system (SASS) scores ranged from 43 (Naro Moru downstream) to 165 (Honi upstream), and there was a decrease in SASS scores with distance downstream. Based on the multimetric index (MI), the Honi and Naro Moru upstream and midstream sites have good water quality (MI: 0.6-0.8), whereas the Honi midstream and downstream sites, and the Naro Moru downstream site, have moderate water quality (MI: 0.4-0.6). Human activities had a negative effect on water quality and habitats. Preventive and conservation measures should be taken in the usage of the Naro Moru and Honi rivers.