Prediction of hyporheic exchange and solute transport dynamics in a headwater tributary of the Illinois and Mississippi River systems

伊利诺伊州和密西西比河系统源头支流的潜流交换和溶质输运动态的预测

• 批准号: 0408744
• 负责人: Aaron Packman
• 金额: $ 36万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0408744&HistoricalAwards=false
• 关键词: Prediction; hyporheic; exchange; solute; transport

0408744PackmanProject Summary: Water and solute exchange between streams and the surrounding subsurface(hyporheic exchange) has recently been recognized as a critical process in the cycling of many importantsubstances in watersheds. Hyporheic exchange has particularly been shown to influence nutrient andcarbon dynamics, and the fate and transport of contaminants in surface waters. These issues have risen tothe forefront in the Midwestern U.S. because substantial nitrate loads from agriculture and urban centerscontribute to chronic hypoxia in the Gulf of Mexico. Despite the clear link that exists between hydrologicprocesses in headwater streams, denitrification efficiency in removing stream nitrate, and nitrogen loadsreaching the Gulf, our current understanding of these processes in low-gradient, sand-bed streams islargely empirical. Most glaring is the lack of, fundamentally-based, predictive models for hyporheicexchange in sand-bed streams, which has prevented the transfer of experimental observations gained atone site to other sites, or even to the same site under different flow conditions.Our objective is to collect a definitive data set from a low-gradient, sand-bed stream and test theapplicability of several fundamental, process based models of hyporheic exchange that have provensuccessful in laboratory flumes. We seek to both advance our fundamental understanding of hyporheicexchange processes in real stream, but also to assess the improvements in prediction of solute transportthat are possible for a variety of flow and geomorphic conditions. The stream selected for intensive studyis Sugar Creek, a headwater stream in the agricultural region along the northern Illinois-Indiana border.Sugar Creek is representative of many low-gradient streams in agricultural headwater areas that aretributary to the Illinois and Mississippi River systems. We propose to conduct detailed tracer experimentsand related physical measurements that will be notable because they will resolve hyporheic flow paths,solute transport, and controlling processes with an unprecedented level of detail. In-stream soluteinjections will be undertaken in several seasons in a 3 to 4 kilometer long reach of Sugar Creek. Stream-tracerdata will be used to assess bulk transport integrated over 8 to 10 sub-reaches (50 300 m long)representing variable geomorphic conditions. Several of those sub-reaches will be thoroughlycharacterized in terms of their streambed topography and morphology, cross-channel flow variability,sediment characteristics, and subsurface movement of the solute tracer. This unprecedented level ofdetail will be made possible using state of the art measurement technologies. The resulting data sets willsupport the application of a suite of fundamental, predictive, process-based models of hyporheic exchangeand its effects on downstream solute transport. The models will be evaluated in terms of their ability topredict not only reach-averaged tracer concentration data, but also point estimates of interfacial hyporheicflux and porewater tracer concentrations. Based on fundamental theory, we will develop and testapproaches for upscaling rates of hyporheic exchange to predict solute transport in the entire study reachunder seasonally varying conditions. In sum, we will apply several modeling approaches of differingsophistication in order to 1) evaluate our current ability to predict hyporheic exchange in sand bed streamsfrom first principles, and 2) develop reasonable approaches for upscaling the computations so that solutetransport can be predicted with a specified level of uncertainty for longer stream reaches.Because this study is focused on fundamental processes that occur widely, this work will have verybroad scientific impacts and will be used to address multiple pressing societal concerns. Detailedunderstanding of the relationship between stream/sedimentary conditions and hyporheic exchange willfacilitate improved understanding of nutrient dynamics, carbon cycling, and releases from contaminatedsediments. Our goals for predictions (in terms of uncertainty and spatial resolution) are compatible withfuture applications in reach and basin-scale water-quality models. In particular, the choice of Sugar Creekas the intensive study site will provide critical hydrologic information to support complementary studieson nitrate fluxes and sedimentary denitrification in the headwaters of the Mississippi River basin. Theproject's broader impacts will also be increased by the synergistic activities of the PI's. Both PI's have astrong history of involvement in scientific organizations, and the project's themes will be reflected inactivities such as special sessions at major technical meetings. We will particularly seek to broaden thegeneral contribution of this work by encouraging interdisciplinary and international communication andinter-site comparisons. The project will also contribute considerably to human resource development,both through direct training of students and via the use of the field site for educational demonstrations.

0408744PACKMANPROJECTS摘要：溪流与周围地下（低音交换）之间的水和溶质交换最近被认为是在流域中许多重要毕业生循环中的关键过程。尤其已显示出低血变交换会影响养分和碳动态，以及地表水中污染物的命运和运输。这些问题在美国中西部已经提升了最前沿，因为农业和城市中心的大量硝酸盐负载到墨西哥湾的慢性缺氧。尽管源头水流中的水文过程存在明确的联系，去除硝酸盐的反硝化效率和对海湾的氮负荷进行的，但我们目前以低梯度的，沙床的水流对这些过程的理解是islargely的经验性。 Most glaring is the lack of, fundamentally-based, predictive models for hyporheicexchange in sand-bed streams, which has prevented the transfer of experimental observations gained atone site to other sites, or even to the same site under different flow conditions.Our objective is to collect a definitive data set from a low-gradient, sand-bed stream and test theapplicability of several fundamental, process based models of hyporheic exchange that have provensuccessful在实验室水槽中。我们试图在实际流中促进对多虫的换速过程的基本理解，而且还可以评估各种流量和地貌条件的溶质运输预测的改进。溪流被选为密集研究的糖溪，这是北伊利诺伊州 - 印度岛沿线的农业地区的源头溪流。SugarCreek代表了伊利诺伊州和密西西比河系统的农业源头地区许多低梯度流。我们建议进行详细的示踪实验和相关的物理测量值，因为它们将通过前所未有的细节水平来解决低音流动路径，溶质传输和控制过程。在几个季节中，将在3至4公里的Sugar Creek河段中进行河流溶质注射。溪流-tracerdata将用于评估代表可变的地貌条件的8至10个子教育（50 300 m长）的整合的散装运输。其中几个子教学将根据其流床的地形和形态，跨通道流动性，沉积物特性和溶质示踪剂的地下运动来彻底表达。使用最先进的水平将使用最先进的水平进行尾声。由此产生的数据集将支持一套基本的，基于过程的基于过程的低音模型，以换取其对下游溶质传输的影响。这些模型将根据其能力不仅具有到达平均的示踪剂浓度数据来评估，还可以评估界面性降压液和毛孔示踪剂浓度的点估计值。基于基本理论，我们将开发和测试对高尺度交换速率的测试，以预测整个研究中季节性变化条件的溶质运输。总而言之，我们将采用几种差异化的建模方法以使其为1）评估我们目前预测第一条原理的砂床流中的低音交换的能力，以及2）2）开发合理的方法来提高计算的范围，以使SolutEtransport可以通过延伸的范围进行跨越的范围来预测，因为该研究的范围很大。并将用于解决多个紧迫的社会问题。详细了解流/沉积条件与低血流向交换之间的关系将使人们对营养动力学，碳循环以及受污染的销量的释放有所了解。我们的预测目标（就不确定性和空间分辨率而言）与覆盖范围和盆地规模水质模型中的图相兼容。特别是，在密西西比河流域的源头中，糖溪的选择强化研究地点将提供关键的水文信息，以支持硝酸盐通量和沉积性硝化作用。 PI的协同活动也将增加项目的更广泛的影响。 Pi的两者都有涉及科学组织的太悠久的历史，并且该项目的主题将反映在主要技术会议上的特殊会议等非活性。我们将特别寻求通过鼓励跨学科和国际交流和网站比较来扩大这项工作的贡献。该项目还将通过直接培训学生以及使用现场地点进行教育示范来为人力资源开发做出巨大贡献。