Do land-cover mosaics affect the variability of suspended sediments in rivers? The case of large river basins in Germany

Abstract

Investigating the influence of land-cover mosaics on water quality is vital for effective management aimed at mitigating the hazard of exceeding regulatory water quality thresholds. In particular, suspended sediments in rivers can easily jeopardize aquatic ecological functions, by transporting significant amounts of pollutants along flow paths. Nonetheless, a relationship between land-cover mosaics and suspended sediment dynamics remains unclear due to the complexity of interactions and feedbacks between geomorphological and hydrometeorological conditions in diverse river basins. Here, we aim to analyse the linkages of landscape metrics describing the spatial patterns of land-cover with the (power-law) rating exponent of suspended sediment concentration SSC and river discharge Q (i.e. SSC = aQb), as an integral property of sediment dynamics. For three major river basins in Germany (Elbe, Rhine, and Weser covering about 66 % of total German territory), the sediment rating parameters are extracted at high flows. Moreover, thoroughly selected descriptors are computed to characterize the composition and spatial configuration of land cover as well as topographic and hydrogeological conditions (e.g., temporal variability in Q and flashiness index). Preliminary results show the existence of correlations between the spatial organization of land cover along the river network and the rating exponent b at high flow regime. In particular, they indicate that high increase in suspended sediments at high flows is generated in catchments with more homogeneous land cover and sediment sources distributed near large streams. Our findings can aid policymakers and watershed managers in making informed decisions and taking necessary actions to improve current and future river water quality issues caused by suspended sediments.