Coordination Funds

下雨的时候水去了哪里？洪水是在哪里产生的，又是如何产生的？赛事期间，什么因素控制溪流水质？这些问题对许多领域都很重要，从工程和防洪到水和生态系统管理以及全球变化影响的预测。在这些问题背后的过程集合中，最难以捉摸的过程是地下风暴流（SSF），它是由侧向地下流触发的快速事件响应。SSF是普遍存在的，并且比一般认为的更重要，因为基于跨尺度和站点的系统研究的基本理解仍然缺乏。然而，只有通过系统的研究，才有可能通过发现SSF功能的一般原理来真正推进我们的理解，并为其评估提供实验和建模方面的协议和最佳实践。在许多自然景观中，SSF，即响应降水事件而发生的任何地下流，在径流生成中起着重要作用：要么直接促成溪流流量，要么产生饱和区域或回流，这是饱和过量陆地流的潜在原因。因此，我们在水文曲线中看到的大部分事件响应可能是SSF的直接或间接结果。SSF的放电信号，包括河流中间接触发的响应，很可能比我们通常假设的要大。虽然它的重要性可能在源头最大，但源头占水系网络的70%，并极大地影响下游水和溶质的供应和运输。然而，由于以下几个原因，SSF难以捉摸且难以解释，测量困难：地下不可接近，空间变异性和异质性大，来源可变，以及它是一个阈值驱动的过程，仅在某些事件中发生。因此，缺乏对SSF的系统研究，主要原因是难以量化。我们建议在不同的环境中，跨尺度地对SSF进行这样的系统研究，并使用精心设计和复制的方法选择，包括新方法。随后将对各种方法和可能的代理进行系统评价，并对模型进行相互比较、评价和改进。因此，我们将重点关注4个挑战：1)开发新的实验方法；2)SSF的空间格局；3)SSF的阈值和级联效应；4)SSF的影响。标准的单一研究项目在一个特定的地点调查这个谜题的一部分，而这个研究单元提供了一个独特的机会，把大量的谜题拼凑在一起。该研究单位将着重强调在四个不同的测试集水区进行的实验工作，然后直接将其纳入协作建模工作，从而在迭代过程中影响实验设计。

Where does water go when it rains? Where are floods generated and how? What controls stream water quality during events? These questions are important to many fields from engineering and flood protection to water and ecosystem management and prediction of impacts of global change. The most elusive processes in the process-ensemble underlying these questions is subsurface stormflow (SSF), the fast event response triggered by lateral subsurface flow. SSF is prevalent and a more important process than generally accounted for because a basic understanding based on systematic studies across scales and sites is still lacking. However, only with systematic studies will it be possible to really advance our understanding by discovering general principles of SSF functioning and to provide protocols and best practices for its assessment, both experimentally and with respect to modelling. In many natural landscapes, SSF, i.e. any subsurface flow that occurs in response to a precipitation event, plays a major role in runoff generation: either by contributing directly to streamflow or by producing saturated areas or return flow, which then is the underlying cause of saturation excess overland flow. Therefore, much of what we see as event response in the hydrograph might be the direct or indirect result of SSF. It is likely that the discharge signal of SSF, including the indirectly triggered response in the stream, is larger than we generally assume. While its importance is probably largest in the headwaters, headwaters make up 70% of the stream network and greatly influence the supply and transport of water and solutes downstream. However, SSF is elusive and poorly accounted for as measurements are difficult for several reasons: the inaccessibility of the subsurface, the large spatial variability and heterogeneity, the variable sources and the fact that it is a threshold-driven process that only occurs during certain events. Thus, systematic studies of SSF are lacking, mainly due to difficulties of quantification. We suggest such a systematic study of SSF in different environments, across scales, and using a well-designed and replicated selection of approaches including novel approaches. This will be followed by a systematic evaluation of methods and possible proxies as well as model intercomparison, evaluation and improvement. Thereby, we will focus on 4 challenges: 1) Development of novel experimental methods,2) Spatial patterns of SSF, 3) Thresholds and cascading effects of SSF, 4) Impacts of SSF.Whereas standard single research projects investigate part of this puzzle at a specific location, this Research Unit provides the unique opportunity of fitting a large number of puzzle pieces together. This Research Unit will have a strong emphasis on experimental work in four different test catchments that then directly feeds into a collaborative modelling effort, which in turn influences experimental design in an iterative process.