This report provides an overall synthesis of Northern River Basins Study research on how developments within the Peace, Athabasca, and Slave river basins have had cumulative impacts on the mainstem and main tributary aquatic ecosystems in the study area. Specifically, the report reviews the key scientific findings in the context of the Study's guiding questions and eight research components: water quality, contaminant distribution, fate and effects, benthos, fish and fish habitat, riparian vegetation and wildlife, hydrology and hydraulics, drinking water quality, nutrients, dissolved oxygen, traditional knowledge, and use of aquatic resources. It also provides an integrated interpretation of the key findings in the context of cumulative effects and contains recommendations related to future aquatic ecosystem management.