Development and testing of a new time variant approach for streamwater transit times

水和污染物在环境中的传输是水文学领域的主要研究挑战。这些过程往往很难或不可能观察到，因为大部分的流动和运输是在地下。由于同位素示踪剂的出现，人们现在可以（在不同的时间）对溪流进行采样，并量化整个流域的过境时间。实际上，水通过集水区的地下到达河流网络所花费的时间（即，集水渡越时间（TT）基本上描述了集水区内的储水量、水流通道异质性和水源。过境时间（TTD）的分布反映了流域如何保留和释放水和溶质，反过来又设置生态地球化学条件，影响污染物的释放或持久性。因此，量化的过境时间分布提供了一个重要的有价值的限制水和污染物的传输对生态地球化学过程和集水区的敏感性，人为输入和土地利用变化。今天，仍然有几个主要的研究挑战，使用TT和了解TT如何能够导致新的突破，在流域流量过程的概念化和新一代水文模型的发展。在该项目中，解决了当前的几个研究问题。总的主题是最近确定的时变行为的TT。在该研究项目的实验任务，高时间采样分辨率的同位素组成的流和降水（15分钟）将被用来调查采样间隔的作用的结果，TT的时变特性和集水参数如何管理的形状的TTD。模型部分处理山坡尺度的TT。我们会采用一个模型，以确定TT和TTD随时间变化的描述，并通过虚拟模型方法确定控制它们的山坡特性。

Water and contaminant transport through the environment are major research challenges across the field of hydrology. These processes are often difficult or impossible to observe because the majority of the flow and transport is below ground. Since the advent of isotope tracers, one can now sample (for a distinct time) the stream and quantify the whole catchment¿s transit time. Indeed the time water spends travelling through the subsurface of a catchment to the stream network (i.e., the catchment water transit time, TT) fundamentally describes storage, flow pathway heterogeneity and sources of water in a catchment. The distribution of transit times (TTD) reflects how catchments retain and release water and solutes that in turn set biogeochemical conditions and affect contamination release or persistence. Thus, quantifying the transit time distribution provides an important valuable constraint of water and contaminant transport on biogeochemical processes and catchment sensitivity to anthropogenic inputs and land-use change. Today there remain several major research challenges for the use of TT and for understanding how TT can lead to new breakthroughs in catchment flow process conceptualization and the development of new generations of hydrological models. In this project several of current research questions are addressed. The overall topic is the recently determined time-variant behaviour of the TTs. Within the experimental tasks of the research project, a high temporal sampling resolution for the isotopic composition of stream and precipitation water (15 min) will be used to investigate the role of the sampling interval on the results, the time-variant characteristic of TT and how catchment parameters govern the shape of the TTD. The modelling part deals with TTs at the hillslope scale. A model will be employed to determine a time variant description of TT and TTD and to identify the controlling hillslope properties on them by a virtual modelling approach.