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Calculation of Emissions into Rivers in Germany using the MONERIS Model
This report illustrates the results of two research projects of the German Federal Environmental Agency that ran parallel: • FKZ 204 24 218: Model-based quantification and internet-based visualisation of emissions into Germany’s rivers („Prioritary substances“) • FKZ 205 24 204: Development of a management tool on emissions into surface waters within the framework of the international reporting commitment („Nutrients“) The aim of both projects was a methodological development of the MONERIS model to quantify emissions from point and diffuse sources into Germany’s surface waters. The following substances were considered: nitrogen (TN) and phosphorus (TP) as nutrients as well as the 7 heavy metals cadmium (Cd), chrome (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) as well as polycyclic aromatic hydrocarbons (PAH). Both projects are based on consistent sub-basins and the according basic data as well as homogenous calculation algorithms that are adapted to the specifications of each substance group. The research encompasses Germany’s large river basins as well as their catchment areas outside Germany and in total covers an area of 650,000 km². This was divided into 3456 analytical units (2759 of those in Germany), the average catchment areas being 190 km² (135 km² in Germany). The modelling was performed in individual annual steps for the period between 1983-2005. For the evaluation of the temporal trends the data was aggregated for the periods 1983-1987 („1985“), 1993-1997 („1995“), 1998-2002 („2000“) and 2003-2005 („2005“) to soften the impact of hydrological influences. All input data was collected and preprocessed with the highest spatial and temporal resolution possible based on the detailed topology. This especially concerns the point sources of communal wastewater treatment plants, mining activities and direct industrial discharges, the use of statistical microdata on wastewater discharge and its treatment, population density, the residence time of groundwater, the calculation of soil erosion based on a de-tailed elevation model, after setting a standard procedure for the complete area as well as river discharge and quality data to calibrate the runoff and test the plausibility of the calculated emissions. The basic data and model results for all sub-basins, years and substance groups of both projects were merged into one database. Additionally, a web-based graphical user interface was developed to visualise the emissions for any area aggregation can be visualised. The completion of both R+D-projects „Nutrients“ and „Prioritary substances“ delivered for the first time ever homogenous instruments that can identify the most important sources and contamination hotspots for different relevant substance groups in larger river basins which can then serve as a basis for further analyses to achieve efficient measures to reduce pollution. Apart from further developing the quantification approaches both projects significantly contributed towards improving the database, which now has a much higher spatial and temporal resolution. According to the detailed topology the emissions are available for each individual sub-basin. However, not all local characteristics of smaller river basins could be integrated adequately when quantifying the emissions due to an incomplete data basis as well as the scale that had to be covered. Furthermore, emissions from sub-basins are subject to a much higher temporal variability, which cannot be adequately retrieved with the help of balance equations for every single year. Accordingly, small areas have a higher deviation between the calculated emissions and the balanced river loads. The model results for small sub-basins are therefore not to be seen as absolute values and predominantly serve as a visualisation of the regional distribution of emissions. These restrictions even more apply to heavy metals and PAH as opposed to nutrients there is only a limited amount of valid measurement data in an adequate resolution for these substances. Pollutants are measured to monitor the compliance to threshold values. In the process some analysis methods use limits of quantification that are too high which is why this data is useless for calculating emissions and immissions. The target-oriented monitoring programmes have to be adapted to current issues under defined and comparable conditions, allowing the monitoring results to be transferred. These programmes are essential for monitoring the effectiveness of the measures taken as well as for emission calculations in medium-sized to small sub-basins.
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