An Ecological Impact Assessment: is defined as a process of identifying, quantifying and evaluating the likely negative effects of a proposed project or development on ecosystems or their components. An aquatic EcIA can provide a scientifically defensible approach to ecosystem management and may be carried out as part of a formal environmental impact assessment (EIA) or to support other forms of environmental assessments or appraisals.
In particular, for hydropower generation a minimum ecological discharge must be provided that ensures good chemical and ecological potential of surface waters and that preserves the streambed and all riverine habitats. A minimum acceptable ecological flow must be provided that maintains aquatic and riparian ecosystem functioning and its species communities. PJSchmid Scientific Consulting conducts aquatic impact studies that provide ecological and statistical assessments of benthic stream communities, hydrophysical and chemical parameters prior and after hydropower dam constructions. These assessments are exemplified by ecological studies and long-term monitoring of the effects of a hydroelectric impoundment in the western Alps. These studies on possible alterations of downstream invertebrate communities after dam construction showed no statistically significant ecological changes. The stream systems sustained species-rich assemblages of benthic algae, protozoans and invertebrates also during periods of low water discharge. Moreover, the saprobic index based on species assemblage of benthic diatoms implied mostly oligosaprobic conditions in this river catchment, conditions that were not altered after dam construction.