Dynamic Groundwater Age Distributions: Exploring Watershed Scale Subsurface Systems

动态地下水年龄分布：探索流域规模的地下系统

• 批准号: 1015100
• 负责人: John Wilson
• 金额: $ 42.31万
• 依托单位: New Mexico Institute of Mining and Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-15 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1015100&HistoricalAwards=false
• 关键词: Dynamic; Groundwater; Age; Distributions; Exploring

Residence times in groundwater systems are referred to in terms of groundwater age and used to diagnose both natural and anthropogenically impacted groundwater behavior. Environmental tracers are employed as proxies to estimate groundwater age, but their application almost always assumes a steady, stationary flow. The effects and importance of transient flow are not accounted for and are unknown. This project addresses non-stationary flows in complex watersheds by accounting for the impacts of temporal variability of weather and climate forcings on groundwater flow and age transport. It uses a two-fold approach. Synthetic systems will be modeled using five-dimensional (5-D), generalized groundwater age models (3-space, 1-time, 1-age) in order to build understanding of controlling processes on groundwater age distributions (GWAD). In transient flows, GWADs are functions of both the time of observation and the time at which observed water entered the system. Preliminary theoretical results show that transient flows bring in processes at all scales, with significant impacts on long-term memory. Then two instrumented and monitored natural watershed systems in the upper Rio Grande of Colorado and New Mexico will be studied. One of these sites is located in the Jemez Mountains of north-central New Mexico and this watershed is part of a Critical Zone Observatory (CZO) funded by NSF. The type, time, and location of new chemical and isotopic tracer measurements will be optimized based on their preliminary 5-D groundwater age models. These applications to natural watersheds will involve undergraduates, link models with data, test the underlying theory and its application, and elucidate how best to use the available suite of tracer methods for GWAD estimation in non-stationary systems. Innovative mathematical solution methods to the 5-D generalized age equations will be developed and tested, including the use of Laplace transforms on age in order to reduce dimensionality. Extensions of these concepts and approaches to residence time distributions in other hydrologic applications, including stream ecology, and to atmospheric science and oceanography where similar problems are encountered in the context of environmental tracers and circulation models, are anticipated.

地下水系统中的停留时间是指地下水年龄，用于诊断自然和人为影响的地下水行为。 环境示踪剂被用作估计地下水年龄的代理，但其应用几乎总是假设稳定的水流。 瞬态流的影响和重要性没有得到考虑并且是未知的。 该项目通过考虑天气和气候强迫的时间变化对地下水流和年龄输送的影响来解决复杂流域中的非平稳流。 它使用双重方法。 将使用五维 (5-D) 广义地下水年龄模型（3 空间、1 时间、1 年龄）对合成系统进行建模，以便加深对地下水年龄分布 (GWAD) 控制过程的理解。 在瞬态流中，GWAD 是观测时间和观测到的水进入系统的时间的函数。 初步理论结果表明，瞬态流动会带来各种尺度的过程，对长期记忆产生重大影响。 然后将研究科罗拉多州格兰德河上游和新墨西哥州的两个仪器和监测的自然流域系统。 其中一个地点位于新墨西哥州中北部的杰梅斯山脉，该流域是 NSF 资助的关键区域天文台 (CZO) 的一部分。 新的化学和同位素示踪剂测量的类型、时间和位置将根据其初步的 5 维地下水年龄模型进行优化。 这些自然流域的应用将涉及本科生，将模型与数据联系起来，测试基础理论及其应用，并阐明如何最好地使用可用的示踪剂方法套件在非平稳系统中进行 GWAD 估计。 将开发和测试 5 维广义年龄方程的创新数学求解方法，包括使用年龄的拉普拉斯变换来降低维度。 预计这些概念和方法将扩展到其他水文应用中的停留时间分布，包括河流生态学，以及大气科学和海洋学，在环境示踪剂和环流模型的背景下会遇到类似的问题。