A predictive diatom-based model to assess the ecological status of streams and rivers of Northern Spain

•A new predictive model to assess the ecological status of rivers of Northern Spain.•4 river types identified were based on their diatom reference communities.•Logistic multinomial Model was used to assign test sites to a river type.•Ecological Quality Ratios estimated from floral similarity with type biological references.•Diatoms responded significantly to eutrophication and intensive agriculture.