During flood events, the water flow through the weir is increased to lower the water level in the lake (the maximum discharge set in the jointly agreed operation rules is 15 mVs), conversely, the weir is more or less closed in times of drought, in order to maintain the water level. The overall trophic situation of the shallow lake is mcso-eutrophic. Lake Neusiedl had a good ecological and chemical status in 2009, according to the requirements of the WFD. Since the 1990s and the early 2000s, the diffuse nutrient load (e.g., nitrate-nitrogen) has markedly decreased.