Monitoring and assessment of macroinvertebrate communities in support of river management in northern Vietnam

The thesis aimed to develop a water quality biological monitoring and assessment based on macro-invertebrates to analyse the status of watercourses and to select sustainable restoration measures in order to support river. The research was carried in the Du river basin in northern Vietnam. Spatial and temporal analysis showed that macro-invertebrate community compositions in the Du river were not only driven by morphological characteristics but also by water quality issues. A relatively small temporal variation was detected that requires no remarkable modifications in the development of a bio-assessment methodology for watercourses in the specific river. Multivariate analyses using CCA and Bray-Curtis cluster analysis provided a similar discrimination between pristine and impacted sites in the Du river basin. Qualitative biotic indices including the BMWP-Viet proved to be appropriate for use in the studied watercourses in Vietnam. The BMWP-Viet could differentiate study sites into classes ranging from very good to very poor ecological conditions. The current BMWP-Viet approach can be useful at an early stage of bio-assessment application in Vietnam. However, this method should be improved by optimising the scoring system for common taxa and development of more robust assessment approaches such as multi-metric indices. Data mining techniques including classification trees and support vector machines were applied to develop predictive models for BMWP-Viet as well as presence/absence of macro-invertebrate taxa (ecological indicators). Optimised models indicate the major environmental variables influencing the presence/absence of macro-invertebrates, which in the mean time also reflect the river characteristics that river managers have to consider in their policy plans. A decision support system, the WFD-Explorer was combined with classification trees to link human activities with the ecological river conditions and analyse the relevance of several restoration options