Collaborative Research: Changes in hyporheic exchange and nitrous oxide generation due to streambed alteration by macro-roughness elements

合作研究：宏观粗糙度元素改变河床引起的流水交换和一氧化二氮生成的变化

基本信息

批准号：
2100927
负责人：
Daniel Tartakovsky
金额：
$ 30万
依托单位：
Stanford University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2021
资助国家：
美国
起止时间：
2021-08-01 至 2024-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2100927&HistoricalAwards=false
关键词：
Collaborative Research Changes hyporheic exchange

项目摘要

Boulders and large cobbles are ubiquitous roughness elements in mountain rivers and their presence provides vital ecological and hydromorphological functions. They are routinely used in restoration projects to increase habitat quality for many aquatic species because they impact on stream morphology by inducing erosional and depositional areas, whose size and extent depend on the boulder/cobble density, sediment inputs, and flow conditions during sediment mobilizing flows. However, little is known about the role of roughness element induced-streambed changes in regulating hyporheic exchange, which is the process moving stream water into and out of stream bed sediments to form the subterraneous hyporheic zone. The hyporheic zone promotes important biochemical transformations, which affect stream and pore water chemistries with implications at both local and global scales because it is a primary driver of bioactivity in streams and a key source of the greenhouse gas nitrous oxide, N2O. Sustainable management of water resources including river restoration (a $1B/year industry in the US) would benefit from knowledge of hyporheic processes to predict the effects of regulated flows, climate, and land use on ecosystems, nutrient cycles, and solute transport at the local and watershed scales. The scientific goal for this project is to understand, quantify, and model the effects of boulder and cobble density and relative sediment supply during forming flows on hyporheic exchange, chemistry, and N2O production during low flow conditions. This will be addressed with flume and field experiments, supported by analytical and numerical modeling, and tested with hypotheses that boulder or cobble-induced changes in streambed morphology (1) have a primary role in regulating both the quantity and chemistry of hyporheic exchange at the reach scale, and (2) alter aerobic respiration, nitrification, and denitrification rates and increase the rates of apparent production and release of N2O.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

巨石和大卵石是山区河流中普遍存在的粗糙元素，它们的存在提供了重要的生态和水貌功能。它们通常用于恢复项目，以提高许多水生物种的栖息地质量，因为它们通过诱发侵蚀和沉积区域来影响河流形态，其大小和范围取决于巨石/卵石密度、沉积物输入和沉积物流动期间的流动条件。然而，人们对粗糙度元素引起的河床变化在调节潜流交换中的作用知之甚少，潜流交换是将河流的水移入和移出河床沉积物以形成地下潜流带的过程。潜流带促进重要的生化转化，影响溪流和孔隙水化学，对当地和全球范围产生影响，因为它是溪流中生物活动的主要驱动力，也是温室气体一氧化二氮（N2O）的关键来源。水资源的可持续管理，包括河流恢复（美国每年 10 亿美元的产业）将受益于潜流过程的知识，以预测调节流量、气候和土地利用对生态系统、养分循环和溶质运输的影响。当地和流域尺度。该项目的科学目标是了解、量化和模拟形成流过程中巨石和卵石密度以及相对沉积物供应对低流量条件下的潜流交换、化学和 N2O 产生的影响。这将通过水槽和现场实验来解决，并得到分析和数值模型的支持，并通过假设进行测试，即巨石或鹅卵石引起的河床形态变化 (1) 在调节流流交换的数量和化学方面具有主要作用。达到规模，（2）改变有氧呼吸、硝化和反硝化速率，提高N2O表观生成和释放速率。该奖项反映了NSF的法定使命，经评估认为值得支持利用基金会的智力优势和更广泛的影响审查标准。