Hydrological modifications drive other ecological stressors of freshwater ecosystems and interact with them. The present paper examines the relevance of hydrological disturbances resulting from global change by presenting the case of the Llobregat River, a highly disturbed system in NE Spain. The Llobregat is a clear example of a Mediterranean river suffering from multiple stressors. Both the distribution and abundance of organisms and ecosystem functioning as a whole are greatly determined by water scarcity, water salinity, nutrient concentration, and organic (and inorganic) pollution. Structural drought exacerbates these problems, as the capacity to dilute pollutants is ompromised. Controlling water abstraction and limiting nutrient and pollutant inputs downstream are essential to the structural and functional recovery of biological communities and to maximizing the ecosystem services provided by the Llobregat River.