Integrated assessment of irrigation channel ecosystem quality in a tropical agroecosystem: linking riparian vegetation, physicochemical gradients, and benthic macroinvertebrate responses

Beyond water conveyance, irrigation channels act as aquatic habitats whose ecological quality is shaped by riparian conditions. However, integrative assessments remain scarce in tropical systems, motivating this study of riparian and non-riparian irrigation channels in Malang, Indonesia. Field sampling was conducted during a single cultivation season using replicated measurements of water and air temperature, pH, electrical conductivity (EC), turbidity, and total dissolved solids (TDS), alongside assessments of riparian vegetation and benthic macroinvertebrate communities. Ecological condition was evaluated using the Shannon–Wiener index (H′), taxa richness (R), importance value index (IVI), and family biotic index (FBI). Irrigation channels with intact riparian vegetation reflected improved physicochemical regulation, evidenced by lower turbidity and reduced ionic enrichment, which coincided with higher macroinvertebrate diversity (H′ up to 2.78). Conversely, non-riparian channels exhibited reduced diversity (H′ as low as 1.56) and were dominated by pollution-tolerant taxa. FBI values corroborated physicochemical and community patterns, shifting from poor–fairly poor conditions in non-riparian channels to fairly poor–fair conditions in riparian channels. Multivariate and principal component analyses consistently revealed strong coupling between physicochemical and biological responses, clearly discriminating riparian from non-riparian channels along an environmental degradation and emphasizing riparian vegetation as a critical structural and functional buffer that enhances ecological and irrigation quality in tropical agroecosystems.