Hydroclimatic control of sediment and metal export from a rural catchment in northwestern Spain

Abstract. This paper examines sediment and metal (Al, Fe, Mn, Cu, and Zn) exportation at different timescales (annual, seasonal and event) during a 3-year period (2005–2008) in the Mero River headwater, a rural catchment under humid temperate climate. Interannual differences were found both in annual loads and their distributions throughout the year. At annual scale, sediment and particulate metal loads followed the same trend as streamflow, while dissolved metals showed different patterns. Runoff events contributed to 63% of the total sediment load, whereas particulate and dissolved loads in events accounted for between 38–61 and 27–49%, respectively. Runoff events were characterized by high variability in sediment and metal loads, a few events representing a high percentage of the metal exported. Sediment loads were related to maximum and initial discharge. Particulate metal loads were highly correlated with sediment loads, runoff being the hydrological variable that best explains the load of these metals. Dissolved metal loads displayed different patterns. Dissolved Al, showed a great correlation with runoff, while dissolved Mn with maximum discharge.