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整个水文学领域的主要研究挑战。这些过程通常很难或不可能观察到，因为大部分流动和运输都在地下。自从同位素示踪剂出现以来，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S渡越时间。实际上，水通过集水区地下流向河网的时间(即集水区水传输时间TT)从根本上描述了集水区内的蓄水量、水流路径的异质性和水源。转运时间(TTD)的分布反映了集水区如何保留和释放水和溶质，而这些水和溶质又决定了生物地球化学条件，并影响了污染物的释放或持久性。因此，通过时间分布的量化为水和污染物的迁移对生物地球化学过程和流域对人为输入和土地利用变化的敏感性提供了一个重要的有价值的约束。今天，对于TT的使用和理解TT如何能够在流域径流过程概念化和开发新一代水文模型方面取得新的突破，仍然存在几个主要的研究挑战。在这个项目中，解决了当前的几个研究问题。总的主题是最近确定的TTS的时变行为。在研究项目的实验任务中，将使用高时间分辨率的溪流和降水的同位素组成的采样分辨率(15min)，以调查采样间隔对结果的影响、TT的时变特性以及集水参数如何控制TTD的形状。建模部分涉及山坡尺度上的TTS。将使用一个模型来确定TT和TTD的时变描述，并通过虚拟建模方法来识别它们上的控制山坡属性。

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.