Hillslope-Riparian Zone Reservoir Mixing: A Multi- Catchment Test of a New Methodology for Predicting Stream Chemistry

9805475 McDonnell了解和预测河流对气候变化和非点源污染物等扰动的化学反应，需要了解控制河流产生的水文机制和影响溶质迁移的生物地球化学机制。尽管对小流域进行了近二十年的密集研究，但还没有出现量化框架来具体说明特定流域的特征所需的测量，甚至没有提供解释实地测量的背景。前人的研究表明，在流域尺度上，山坡-河岸水库的混合可能是对河流化学最重要的控制。我们将在3个流域(帕诺拉山、休眠河和新西兰迈迈)进行一项横跨各种地貌和水文条件的山坡-河岸带混合的野外模拟研究。我们的研究是基于这样的认识：(1)在暴雨期间，山坡对径流可能没有太大的直接贡献；(2)在风暴发生期间，山坡的化学特征在溪流中并不明显，从而挑战了我们传统的认为溪流是流域的集成者的观点；(3)我们可能无法建立基于溪流化学和水文学的整个(包括山坡)集水模型来预测未来的情况。最终目标是客观地将集水区(基于规定的测量)划分为均质水库，以提供解释现场观测和开发预测模型的一般方法。这些水库之间的物理联系决定了集水区内的水文流动路径。通过在多个集水区工作，我们希望能够辨别出不是某一种化学物质所特有的模式。将使用不确定性分析。我们的目标是：(I)开发一个新的基于TOPMODEL的水文地球化学水库混合，以测试我们对水流路径和径流产生机制的感知理解，这与水文测量一致；(Ii)利用分水岭交叉比较，确定什么集水区因素决定了山坡对河流化学的影响；(Iii)量化山坡水何时变成河岸水；(Iv)开发一个基于数据的水库混合模型，该模型具有坚固的结构，广泛适用于高地集水区。这项研究代表了一种创新的尝试，将受同位素和地球化学数据约束的水库混合模型与流域尺度的地形驱动的水文模型联系起来。

9805475McDonnellUnderstanding and predicting streamwater chemical response to perturbations such as climate change and non-point source pollutants requires knowledge of the hydrologic mechanisms controlling streamflow generation and biogeochemical mechanisms influencing solutes transport. Despite the nearly two decades of intensive research in small catchments, no quantitative framework has emerged that specifies the measurements necessary to characterize a given catchment or even provides a context for the interpretation of field measurements. The proposed project seeks to develop such a framework through a combined modeling and field effort.Previous research has indicated that hillslope-riparian reservoir mixing may be the most important control on stream chemistry at the watershed scale. We will conduct a field-modeling study of hillslope-riparian zone mixing at 3 catchments (Panola Mountain, Sleeper River and Maimai New Zealand) spanning a wide range of geomorphic and hydrologic conditions. Our research is based on realizations that: (1) the hillslope may not contribute much directly to streamflow during storm events, (2) the chemical signature of the hillslope is not apparent in the stream during events, thus challenging our traditional view of the stream as integrator of the catchment, and (3) we may not be able to construct whole (including the hillslope) catchment models based upon stream chemistry and hydrology for prediction of future conditions. The ultimate goal is objective delineation of catchments (based on prescribed measurements) into homogeneous reservoirs to provide a general methodology to interpret field observations and develop predictive models. The physical connections among these reservoirs define the hydrologic flowpaths in the catchment. By working at multiple catchments, we hope to be able to discern patterns that are not specific to one catchemtn.Uncertainty analysis will be used. Our objectives are to: (i) develop a new TOPMODEL-based hydrogeochemical reservoir mixing to test our perceptual understanding of flow pathways and runoff production mechanism, consistent with hydrometric measurements, (ii) determine what catchment factors determine hillslope influence on stream chemistry using a watershed cross-comparison, (iii) quantify when hillslope water becomes riparian water, (iv) develop a data-based reservoir mixing model with robust structure to apply generally to upland catchments. This study represents an innovative attempt to link a reservoir mixing, model constrained by both isotope and geochemical data within a topographically-driven hydrologic model at the catchment scale.