Modelling of suspended sediments in the Upper Danube with SWAT

Suspended sediments are nonpoint-source pollutants that threaten the good ecological status of the Danube River. The Soil and Water Assessment Tool (SWAT) integrated watershed model can be used to test management scenarios to reduce sediment loads and achieve water quality targets, such as those set in the European Water Framework Directive. The aim of this study was to calibrate and validate the SWAT sediment model to simulate suspended sediment loads in the Upper Danube, thus enabling management scenario assessment. The Upper Danube Basin, stretching from its sources down to the Gabickovo Reservoir, covers an area of approximately 132000 km2, subdivided in about 750 subcatchments. The simulation period was 1990-2009, inclusive of five years of model warm-up. The model set-up comprised land use map derived from CORINE 2000 and adjusted for crop statistics, the European Soil Map, and a Digital Elevation Model of 100 m pixel size. A regionalized calibration and validation of water quantity was conducted prior to sediment modelling to ensure that monthly water balance and discharge components were correctly represented. Soil erodibility was set to account for climate, stoniness, and topsoil texture. A two-step, multi-site, and spatially-split calibration and validation approach was pursued to improve the sediment budget assessment. In the first step, hillslope parameters (the MUSLE C and P factors) were calibrated so that sediment yields generally matched erosion measured in published soil loss data for temperate zones. In the second step, stream shear power and shear stress parameters were calibrated against monitored data at annual time steps matching suspended sediment concentration (mg/L) time-series. Data of 19 monitoring stations were used in the calibration zone (the Danube upstream of the Naab junction, the Inn, and the Morava River Basins), and 14 in the validation zone (the Naab, the Isar and the Danube downstream of the Naab junction). Results of this initial calibration of the Upper Danube yielded good estimates of hillslope erosion and of sediment concentrations at some gauging stations. However, further work is required to improve sediment concentration predictions. Inclusion of detailed spatial information to define reach conditions (vegetation, sediment characteristics, engineering interventions) is expected to improve SWAT pre-dictions further.

VIGIAK Olga;  MALAGO Anna;  BOURAOUI Faycal;  HABERSACK Helmut; 

2014-10-02

Deggendorf Institute of Technology

JRC91382

https://publications.jrc.ec.europa.eu/repository/handle/JRC91382,