2), using the proportion calculated by MONERIS, which was vice versa used to estimate the historical river loads. MONERIS allows simulation and tracking of nutrients from the emission source through the environment to the river mouth. It is based on a geographical information system (GIS), which includes various digital maps and extensive statistical information. MONERIS is applied to calculate riverine nutrient emissions from the German Baltic river

basin, considering also nutrient retention in the river and providing monthly loads at the river mouth. Behrendt and Dannowski [3] and Venohr et al. [53] present details about the model. A comparison between observed and model simulated N and P loads for the period 1983–2005 is documented in Venohr et al. [52]. MONERIS model simulations SB203580 in vivo for the years around 1880 were based on historical statistic data sets and compiled literature data. The German Baltic river basins cover an area of 28,600 km2 or about 2% of the Baltic Sea catchment [23]. In 1880, arable land covered 55%, forests 18% and grassland 15% of the catchment. Agriculture Tacrolimus mouse already covered an area comparable to the present situation, but was still not intensified with only limited application of manure. The nitrogen surplus (difference between

fertilizer application and removal with harvest) was still close to zero. Tile drainage and sewer systems were already in Teicoplanin place. The total human population in the catchment was 1.4 million, roughly 50% less than today. Details about approach and results are described in [27]. Two ERGOM-MOM model simulations were carried out. The first covered the present situation between 1970 and 2008. The average annual German Baltic riverine loads, for example, for the years 2000 until 2008 were about 21,100 t total nitrogen (TN) and 474 t total phosphorous (TP) with an N to P relationship of 39. The second simulation covered the historical situation, using the loads provided by MONERIS for the years around 1880. The historic annual German Baltic riverine loads were 5127 t TN and 227 t

TP (molar N/P=44). The historic run covered the years 1875 until 1885. In subsequent calculations, the simulation results were averaged over the period 2000 until 2008 resp. 1881 until 1885 to reduce the effects of interannual variability and the model dependency on initial starting conditions. To calculate maximum allowable German nutrient inputs and subsequent target concentrations for German rivers, a simplified, spatially integrated approach was used, that allows a direct comparison to existing MAI and the BSAP. The annual DIN and DIP loads and average chl.a concentrations were extracted from model simulations for an area, which is known to influence water quality in the German Baltic Sea (9.5°–14.8°east, 53.6°–55.35°north). To extend the data set, earlier ERGOM-MOM simulations [20] and [31] were additionally considered. Chl.