Water flux and nitrogen cycling in the hyporheic zones of a semi-arid watershed: Hydrologic and geomorphic driving forces in a transitional climate

半干旱流域潜流区的水通量和氮循环：过渡气候中的水文和地貌驱动力

• 批准号: 0450317
• 负责人: Donald Siegel
• 金额: --
• 依托单位: Syracuse University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-05-15 至 2011-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0450317&HistoricalAwards=false
• 关键词: Water; flux; nitrogen; cycling; hyporheic

0450317SiegelHyporheic exchange, the temporary storage of surface water in stream bank sediments, affects the transport of solutes, including nutrients, through watersheds. Water diverted into the hyporheic zone has a longer residence time and more interaction with biogeochemically active sediments than water in other flow paths. Hyporheic flux rates and geochemistry have not been studied in semi-arid intermountain watersheds, transitional in climate between alpine catchments and desert lowlands. Hyporheic exchange in watersheds in humid regions is enhanced by stream meanders, variable flow rates, and sediment hydraulic conductivity. In water poor regions other geomorphic characteristics, particularly beaver dams, may equally influence hyporheic exchange. We propose to complete an intensive study of hyporheic interaction and nitrogen uptake potential in an intermountain semi-arid watershed with significant beaver activity. The study will include field experiments and numerical hydrologic models designed to 1.) identify and quantify hyporheic pathways and fluxes of water and dissolved solutes across the surface-groundwater interface and 2.) identify the causes of hyporheic flux variability. We will test the hypothesis that in-stream flow obstructions, particularly small beaver dams, particularly enhance the extent of the hyporheic zone along semi-arid streams compared to the effects of other geomorphic and hydrologic controls. We will test our hypothesis by inversely modeling a series of in-stream tracer tests to characterize hyporheic storage parameters along various reaches of Red Canyon Creek, Wyoming. We will use Darcy flux calculations and observations of tracers at near-stream wells to independently test the results of the in-stream tracer tests. We will test the hypothesis that reaches with a greater degree of hyporheic interaction have a greater potential for uptake of nitrate. Dissolved nitrate will be paired with the conservative tracers during in-stream tracer tests. Using the rate of decline of nitrate concentrations downstream, measurements of ammonia and other nitrogen species, and an exponential nutrient uptake model, we will quantify nitrogen uptake lengths along Red Canyon Creek and compare these results with hydrologic measures of hyporheic exchange. Furthermore, we will do microbial investigations incorporating molecular techniques and analysis of the geochemistry of near-stream waters to independently evaluate the degree to which denitrification and nitrogen uptake drives nitrogen processing in the hyporheic zone. Results of in-stream tracer tests are empirical in nature, and therefore difficult to generalize to other sites. For this reason, we will use three-dimensional numerical computer models of near-stream flow paths to evaluate the physical processes controlling the aerial extent and flux of water through hyporheic zones. The results of these models will be combined with detailed measurements of stream geomorphological and sedimentological characteristics in a series of multivariate geostatistical approaches to explore what stream characteristics most affect hyporheic exchange in the study setting and in similar order streams elsewhere. This project will build on the ongoing collaborative relationships between Syracuse University, the University of Missouri's Branson geology field camp, and the Wyoming Nature Conservancy. Previous collaborations between these institutions have resulted in hydrologic instrumentation of part of the Red Canyon Creek watershed for student research and education in fields from glacial history to ecology. We will build on this previous work, enhancing the site with instrumentation that will provide research grade hydrologic data at a watershed scale. Through this project, students from across the Nation studying at the Branson geology field camp will have unprecedented access to a broader range of hydrogeological field experiments at a wider variety of sites within the Red Canyon Creek watershed. In addition, students from Central Wyoming College, a 2-year community college with a large Native American enrollment, will be recruited to participate directly as summer research assistants for the project. These collaborations, undergraduate through graduate in level, will potentially have broad educational impact at both the local and larger scale.

0450317 SiegelHyporheic交换，地表水在河岸沉积物中的临时储存，影响溶质的运输，包括营养物质，通过流域。 与其他流动路径中的水相比，转入潜流带的水具有更长的停留时间，并且与地球化学活性沉积物的相互作用更大。 在半干旱山间流域，高山集水区和沙漠低地之间的气候过渡，潜流通量率和地球化学还没有研究。 在湿润地区的流域，潜流交换增强流曲流，可变流速，和沉积物水力传导。在缺水地区，其他地貌特征，特别是河狸坝，可能同样影响潜流交换。我们建议完成一个深入的研究，在山间半干旱流域具有显着的海狸活动的潜流相互作用和氮吸收潜力。 该研究将包括实地实验和数值水文模型，旨在1。确定和量化地表-地下水界面上的水和溶解溶质的潜流路径和通量，以及2.）找出导致低流量变化的原因。 我们将测试的假设，在流的流动障碍，特别是小海狸坝，特别是提高的程度，低流区沿着半干旱河流相比，其他地貌和水文控制的影响。 我们将测试我们的假设，通过逆向模拟一系列的流中示踪剂测试，表征沿沿着不同的红峡谷溪，怀俄明州河段的潜流存储参数。 我们将使用达西通量计算和近流威尔斯井示踪剂的观测结果来独立检验流中示踪剂测试的结果。我们将检验这一假设，即具有更大程度的潜流相互作用的河段具有更大的硝酸盐吸收潜力。 在流中示踪剂测试期间，溶解的硝酸盐将与保守示踪剂配对。 使用硝酸盐浓度的下降率下游，氨和其他氮物种的测量，指数养分吸收模型，我们将量化氮吸收长度沿着红峡谷溪和比较这些结果与水文措施的潜流交换。 此外，我们将进行微生物调查，结合分子技术和近流沃茨的地球化学分析，以独立评估反硝化和氮吸收驱动潜流带氮处理的程度。流中示踪剂试验的结果本质上是经验性的，因此难以推广到其他地点。 因此，我们将使用近流路径的三维数值计算机模型来评估控制通过低流区的水的空中范围和通量的物理过程。这些模型的结果将结合流地貌和沉积特征的详细测量，在一系列的多元地质统计方法，探索什么流特性最影响潜流交换的研究设置和类似的顺序流在其他地方。该项目将建立在锡拉丘兹大学、密苏里州大学布兰森地质野外营地和怀俄明州自然保护协会之间正在进行的合作关系的基础上。 这些机构之间以前的合作，导致了部分红峡谷溪流域的水文仪器，学生的研究和教育领域，从冰川历史生态。 我们将建立在这一以前的工作，加强与仪器，将提供研究级水文数据在流域规模的网站。 通过这个项目，来自全国各地的学生在布兰森地质野外营地学习将有前所未有的机会获得更广泛的水文地质野外实验在更广泛的各种网站内的红峡谷溪流域。 此外，来自中央怀俄明州学院的学生，一个2年制的社区学院，有大量的美国原住民入学，将被招募直接参与作为该项目的夏季研究助理。 这些合作，本科到研究生的水平，将有可能在当地和更大规模的广泛的教育影响。