By the 1990s, the Segura had become one of the most polluted rivers in Europe, due to the canning industry and urban and agricultural residues originating in the densely populated area in the medium and lower areas of the basin. This fact combined with low or extreme low flows in the same areas –the agricultural use of water and summer drought could reduce the mean discharge to just around 2 to 3 m/s in Murcia city– made more difficult to dilute pollutants.