Nutrients and organic matter in a glacial river—floodplain system (Val Roseg, Switzerland)

Abstract

Nutrient and organic matter dynamics were evaluated for a glacial river—floodplain system in the Swiss Alps (Val Roseg). Glacial melt water was the primary source of particulate organic and inorganic matter; hillslope groundwater was richest in DOC and SiO2; and pulses in dissolved nitrogen were identified during spring snowmelt. Calculations of temporal coherency revealed that hydrological processes within the catchment—floodplain complex controlled nutrient and organic matter species along the main channel; however, local hydrological and/or biogeochemical processes played a major controlling role in most floodplain channels. DON and NO3−N were the only variables that were in average significantly correlated across all sampling sites. Comparisons of measured concentrations and concentrations based on a two end member mixing model indicated that the floodplain served as a major sink for particulate phosphorous and suspended matter but was never a source for nutrients or organic matter. Annual area‐specific export rates from the Val Roseg catchment were 7.6 kg ha−1 yr−1 for TOC (47% DOC), 4.3 kg for TP (98% particulate phosphorus), and 4.1 kg for TN (78% NO3−N).