Riparian Vegetation as an Ecological Indicator of River Health: A Case Study of Isiukhu River, Kenya

Abstract

Riparian zones have significant impacts on the ecological health of rivers. However, it’s unclear whether riparian vegetation can be used as effective indicators of ecological health in Afro-tropical rivers. Therefore, this study assessed Isiukhu River health using riparian vegetation as a bio indicator in Kenya. The study was conducted between September 2023 to December 2023. To achieve this objective, water quality was determined using in-situ techniques while macroinvertebrates were collected using D-frame net and identified using appropriate keys. Sentinel – 2A images identified riparian types - natural forest, grassland, agriculture and urban settlements within the study area. Identified riparian types were confirmed through ground-truth visualization with the aid of transect walks. The condition of the identified riparian types was classified and rated respectively as very high (4), high (3), moderate (2), and low (1).  ANOVA and Pearson correlation coefficient were employed in data analysis. Statistical analysis revealed a significant variation in water quality across riparian cover types (F (5,19) = 11.39, ρ <0.05), physicochemical characteristics of river water was influenced by condition of riparian cover. 1,350 macroinvertebrates belonging to 12 orders, 30 families and 30 genera were collected. There was a significant positive correlation between the genera abundance and riparian cover types (r=0.9633; ρ < 0.05), suggesting that natural riparian vegetation supports higher species abundance due to resource availability and a complex natural habitat. Although other diversity indices showed positive but non-significant correlation with riparian covers (ρ > 0.05), the consistent direction of relationship implies riparian vegetation enhances riverine ecological integrity. The findings confirm that different riparian types influence site-specific water quality, macroinvertebrates abundance and diversity, highlighting their importance as reliable ecological indicators of river health.  Therefore, this reinforces the need for targeted riparian zone restoration to enhance water quality and biodiversity in the Isiukhu River and other world’s rivers.