Structurally optimized modeling of non-linear effects of meteorological extreme events on water and solute dynamics

地下水和溪流水质受到多种过程的影响，这些过程在不同的尺度上起作用，并且经常以高度非线性的方式相互作用。因此，很难区分人为影响和自然变率的影响，例如年际气候变率和长期气候变化。通常，一些单一事件对系统行为的决定作用要比长期平均条件大得多。这使得对预期的气候变化（包括气象极端事件的频率和强度的变化）对水质的影响进行合理评估变得困难。自1986年以来，Lehstenbach流域一直是众多生物地球化学过程研究和广泛监测的焦点。所获得的数据为研究不同过程之间的相互作用，将上坡土壤和地下水与河岸湿地和溪流联系起来提供了理想的基础。利用非线性统计，开发了一种方法，并将其应用于数据，从而可以确定流域尺度上的主要过程。这一信息有助于优化基于物理的流域水流、溶质运移和周转量数值模型的模型结构（模型中明确包含的过程和数据），从而整合流域尺度上单一过程研究的结果。优化后的模型可用于研究近期气候变率对流域溶质周转的影响，从而为情景分析提供工具。因此，它可以帮助将Forschergruppe不同工作组的发现联系起来，形成对整个系统水流和溶质运移行为的整体描述。

Groundwater and stream water quality are affected by a multitude of processes that act at different scales and often interact in highly non-linear ways. As a consequence, the effects of anthropogenic impacts and natural variability, e.g. interanual climatic variability and longterm climate change are difficult to differentiate. Often, a few single events are much more decisive for the system's behavior than long-term mean conditions. That renders a sound assessment of the impacts of expected climate change, including changing frequencies and intensities of meteorological extreme events, on water quality difficult The Lehstenbach watershed has been the focus of numerous biogeochemical process studies and extensive monitoring since 1986. The obtained data provide an ideal basis for studying the interplay between different processes, linking upslope soil and groundwater bodies with riparian wetlands and streams. Using non-linear statistics, a methodology has been developed and applied to the data that allows an identification of prevailing processes at the watershed scale. This information shall be used to optimize model structure (processes and data explicitly included in the model) of a physically based, numerical watershed model for water flow, solute transport and turnover that would allow an integration of the findings of single process studies at the watershed scale. The optimized model can be used to study the effect of recent climatic variability on watershed solute turnover, and thus provide a tool for scenario analyses. As such it can help to link the findings of the different working groups of the Forschergruppe into an integral description of total system's water flow and solute transport behavior.