Several practical concepts and software systems have been recently developed in the issue of environmental decision support. However, the application of ecological modelling approaches that integrate hydrodynamic, physical-chemical, and biological components sub-models for predicting macroinvertebrates in rivers, is rather limited and hardly described in literature. The Cauca river is one of most severe cases of contamination for domestic and industrial wastewater discharges in Colombia. One of the most sensitive problems in the Cauca river is the decrease of dissolved oxygen with concentrations near to zero (0) mg/l in some monitoring stations especially during dry season (low flows). Low DO levels affect the ecosystem equilibrium and the functioning and survival of biological communities. In this research an integration of habitat suitability models with the hydrodynamic and physical-chemical water quality model MIKE11 was performed. Ecological models (statistical models) that allow predicting the occurrence and the abundance of macroinvertebrates (Ephemeroptera, Trichoptera and Haplotaxida) in this river under different conditions were built. The integrated ecological model allows to model and to assess the ecological impact of wastewater discharges into the Cauca river and can help to calculate the needed reductions in discharges of organic matter to meet biological quality criteria in this river
