Collaborative Research: Investigating Timescales of Hydrologic Transport in Catchments Using Natural Tracer Time Series, Theoretical Models, and Laboratory-Scale Simulations

合作研究：利用自然示踪时间序列、理论模型和实验室规模模拟研究流域水文输送的时间尺度

• 批准号: 0125338
• 负责人: Xiahong Feng
• 金额: $ 3.92万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-03-01 至 2006-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0125338&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Timescales; Hydrologic

0125338Feng The travel time of water through a catchment -- that is, the time it takes for rainfall to reach the stream -- is a fundamental hydraulic parameter controlling the persistence of soluble contaminants, and thus the downstream consequences of pollution episodes. A catchment is characterized by a distribution of travel times, reflecting the diverse flow paths that rainfall can take to the stream. Thus, quantifying catchments' travel time distributions should help to clarify the hydrologic mechanisms controlling flow routing in the subsurface. Understanding the timescales of transport and storage in catchments is also important for predicting how rainfall inputs will be chemically modified by reactions with catchment soils and bedrock. But despite the importance of catchment travel time distributions for watershed hydrology and geochemistry, they have rarely been quantified and the mechanisms controlling them are poorly understood. Catchment travel time distributions can be inferred from long-term time series of inert tracers, such as chloride, in rainfall and streamflow. It has recently been shown that catchment travel-time distributions can have unexpectedly long "tails", implying that they can retain soluble contaminants for much longer than would otherwise be expected [Kirchner, Feng, and Neal, Fractal stream chemistry and its implications for contaminant transport in catchments, Nature, 403, 524-527, 2000]. The proposed research program builds on this recent work, and has four main components:a) analyses of long-term time series of rainfall and streamflow concentrations of chloride (a naturally occurring nonreactive tracer) from humid forested catchments in diverse geological settings, using spectral, autocorrelation, and cross-correlation methods to infer each catchment's characteristic travel time distribution,b) development and testing of alternative conceptual models for the observed travel-time distributions, c) construction of laboratory-scale physical models to simulate the hypothesized mechanisms underlying these conceptual models, andd) analyses of reactive tracer data, to complement the passive tracer (chloride) studies. This integrated program of data analysis, conceptual modeling, and laboratory-scale physical models is designed to clarify the mechanisms that control catchment-scale transport, storage, and mixing of waters and their associated solutes. This project is expected to lead to:a) improved understanding of catchment flowpaths and travel time distributions, and the factors controlling them,b) improved understanding of how catchment flowpaths, and reactions between aqueous and solid phases, affect the mobility of reactive solutes at catchment scale,c) improved tools for using hydrologic and geochemical time series to probe the internal workings of catchments, andd) improved methods for testing catchment flow and routing models through comparisons with field data.

水通过集水区的传播时间--即降雨到达溪流所需的时间--是控制可溶污染物的持久性，从而控制污染事件的下游后果的基本水力参数。集水区的特点是旅行时间的分布，反映了降雨可以带到溪流的不同流动路径。因此，量化集水区的行程时间分布应该有助于阐明控制地下径流的水文机制。了解集水区运输和储存的时间尺度对于预测降雨输入将如何通过与集水区土壤和基岩的反应而发生化学变化也很重要。但是，尽管流域行程时间分布对流域水文学和地球化学很重要，但很少有人量化它们，而且对它们的控制机制也知之甚少。从降雨和径流中惰性示踪剂(如氯化物)的长期时间序列可以推断集水区行进时间分布。最近的研究表明，流域传播时间分布可能有出人意料的长“尾巴”，这意味着它们可以将可溶污染物保留的时间比预期的要长得多[基什内尔、冯和尼尔，分形流化学及其对流域中污染物传输的影响，自然，403,524-527,2000]。拟议的研究计划建立在最近这项工作的基础上，包括四个主要部分：a)分析不同地质环境下潮湿森林流域的降雨量和径流氯(一种自然产生的非反应性示踪剂)的长期时间序列，使用光谱、自相关和互相关方法推断每个流域的特征行程时间分布；b)为观测到的行程时间分布开发和测试替代概念模型；c)构建实验室规模的物理模型以模拟这些概念模型所依据的假设机制；以及d)分析反应性示踪剂数据，以补充被动示踪剂(氯)研究。这个数据分析、概念建模和实验室规模物理模型的集成程序旨在阐明控制流域范围内水域及其相关溶质的运输、储存和混合的机制。预计该项目将有助于：a)提高对汇流路径和旅行时间分布及其控制因素的了解；b)提高对汇流路径以及水和固相之间的反应如何影响汇流规模上活性溶质流动性的理解；c)改进利用水文学和地球化学时间序列来探索汇流内部机制的工具；d)改进通过与现场数据进行比较来测试汇流和汇流模型的方法。