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5H - Catchment area mgnt (WEP/214) River load estimations for substance fluxes analysis: Accuracy of estimation methods in dynamic situations. Gallé, Tom1, Kurtenbach, Andreas2, Welfring, Joelle1, Weidenhaupt, André1, 1 Resource Centre for Environmental Technologies CRP- Henri Tudor, Esch/Alzette, Luxembourg, Luxembourg2 Dept. of Hydrology University of Trier, Trier, Germany, Germany ABSTRACT- Substance fluxes analysis is an important tool in catchment area management. Proper estimation of the actual river loads often suffers from limited resources to do frequent sampling.The compromise consists in most cases in taking weekly or biweekly samples and relying on a stochastic probability that all hydrological and life-cycle situations have been measured. Load calculations can be performed from this dataset either by extrapolation with discharge, which is often available at high resolution, or by interpolation techniques with different weightings. While low-flow situation can be characterized quite easily because of little variation, floodwaves vary substantially in their loads, especially for particle-bound substances. Sources for particulate material are limited and are strongly dependent on pre-wave conditions. This weakens the discharge-concentration relationships considerably. We′re conducting a sampling campaign that is relying on the stochastic principle of weekly samplings but additionally monitors the river online for turbidity and conductivity and uses automatically triggered autosamplers for high-frequency sampling of floodwaves. Parameters that are measured cover suspended matter, particulate (POC) and dissolved (DOC) organic carbon, nutrients, dissolved and acid available metals (AAP) as well as particle size measurements with a CIS Laser counter. We use different approaches to calculate fluxes, like extrapolation from discharge, conductivity and turbidity and test these with datasets of different resolutions (weekly sampling data, specific autosampled events). One question that will be highlighted is for instance the transferability of calibration data for suspended matter calculation from turbidimetric measurements from one flood event to another. Other topics include variation in metal content of suspended matter over the flood event as well as its link to POC and particle size data. Accuracy and precision of different load estimation methods in dynamic situations will be discussed. Key words: metals, load, suspended matter, extrapolation |
