The Influence of Catchment Characteristics on the Water Chemistry of Mountain Lakes

Forty-four lakes in the Austrian Alps were studied to examine the influence of catchment characteristics on water chemistry. The lakes are located along an altitudinal gradient (1502-2309 m a.s.l.) in a small study area (35.5 km * 15.5 km) without glaciers. Longitude and latitude accounted for 21.4% of the variation in water chemistry. Bedrock mineralogy explained 14.5% of the variation. Vegetation accounted for 13.2% and slope for 5.5% of the variation in water chemistry. No correlations were found between exposure and water chemistry. Water chemistry appeared to be mainly determined by (1) chemical weathering of carbonate minerals and (2) in-lake productivity. Carbonate minerals were assumed to be present in all watersheds. Trees and shrubs enhanced chemical weathering. Concentrations of chemical parameters indicating physical weathering were high in lakes with large, steep catchments. Steep watersheds were correlated with enhanced nitrogen concentrations in the lakes. In-lake productivity obscured relationships between chemical parameters and catchment characteristics. Nonetheless, catchment characteristics explained 45% of the variation in water chemistry, stressing their importance for water chemistry in mountain lakes.