Dominant controls on catchment water quality dynamics: A Germany-wide analysis using data-driven models

清洁水的供应是联合国2030年可持续发展的全球目标之一。在中欧和德国，向地表水、地下水和最终向海洋环境输入营养物质仍然是水生生态系统和供水的一条主线。在集水区范围内，众多相互关联的进程和投入途径阻碍了有效管理所需的机械性理解和明确的因果关系。在过去的几十年里，人们在改善废水处理方面做出了很大的努力，以减少向地表水输入的点源磷和氮。然而，由于运输时间滞后和遗留影响，来自农业来源的分散投入仍然很重要，很难管理。因此，减少农业氮素过剩的措施对下游水质的影响往往很难预测。这项建议利用了德国全国唯一的水质和水量数据集。这一数据是基于德国联邦各州的定期水质监测，由UFZ编制。通过数据驱动的分析，使用浓度和浓度-流量关系的模式来总结流域尺度上的主要过程和输入路径。该提案侧重于三个目标：(A)根据过去几年(2010年以前)的养分出口制度对流域进行分类。(B)随着输入途径的变化，较长时间序列中氮磷比的时间发展。(C)从集水区输出养分的长期轨迹，以及朝着化学稳定条件的可能发展。创新的数据驱动方法和独特的数据集使人们能够以新的视角看待人类改造景观的中欧环境中养分出口的主导控制。这一结果将为流域尺度的降低复杂程度的水质模型提供一个起点。此外，结果将对更广泛的学科感兴趣，如水生生态学和环境管理。

The availability of clean water is one of the United Nations global goal for sustainable development 2030. In Central Europe and Germany elevated inputs of nutrients to surface water, groundwater and finally to marine environments is still a thread for aquatic ecosystems and water supply. At catchment scale the multitude of interrelated processes and input pathways hinder a mechanistic understanding and a clear cause-effect relationship that is needed for effective management. In the last decades great efforts have been put into the improvement of wastewater treatment to reduce point source inputs of phosphorus and nitrogen into surface waters. However, diffuse inputs from agricultural sources are still important and hard to manage as a result of long transport time lags and legacy effects. Consequently, the effects of measures to reduce nitrogen surplus from agriculture on the downstream water quality are often hard to predict. This proposal utilizes a unique dataset of water quality and water quantity across Germany. This data is based on the regular water quality monitoring of Germany's federal states and was compiled by the UFZ. By means of a data-driven analysis, patterns in the concentration and concentration-discharge relationships are used to conclude on dominant processes and input pathways at catchment scale. The proposal focusses on three aims: (a) The classification of the catchments with regards to nutrient export regimes for the last years (younger than 2010). (b) The temporal development of nitrogen:phosphorus ratios for longer time series with changing input pathways. (c) The long-term trajectories of nutrient exports from catchments and the possible development towards chemostatic conditions. The innovative data-driven methods and the unique dataset allow a new view of dominant controls of nutrient exports in the Central-European settings of anthropogenically modified landscapes. The results will be a starting point for complexity reduced water quality model at catchment scale. Moreover, results will be of interest to a broader range of disciplines such as aquatic ecology and environmental management.