The water quality of Icelandic rivers is controlled by a number of natural and anthropogenic factors interacting at complex spatial and temporal scales. This article presents the findings of a study into the water quality of two Icelandic rivers; the Blanda and the Skjálfandafljót. The study investigated the impact of three of the factors influencing water quality in these rivers: impoundment for hydro-electric power generation; agricultural land use; and the presence of glacial and periglacial areas. The results indicate that impoundment within a reservoir was responsible for a significant reduction in turbidity and a significant drop in aluminium concentrations as the reservoir acted as a sediment trap and chemical sink. Agricultural land use was found to have no significant effect on the nitrate or phosphate concentrations. Increasing glacial influence was found to be associated with increased turbidity but decreased total dissolved solids. Finally, the presence of permafrost soils in the periglacial highlands of the Blanda was positively associated with aluminium concentrations.