IMPACT OF MACROPORES AND SOIL PIPES ON HYPORHEIC EXCHANGE IN STREAMS

大孔和土管对河流水流交换的影响

• 批准号: 1446481
• 负责人: Erich Hester
• 金额: $ 25.24万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2020-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1446481&HistoricalAwards=false
• 关键词: IMPACT; MACROPORES; SOIL; PIPES; HYPORHEIC

Streams and rivers form a vital part of the water cycle, are 'downstream of everything" and are most affected by most human actions. It is therefore important to understand how stream and rivers work so we can account for these benefits and anticipate how they may respond to trends like urbanization. The hyporheic zone is the boundary between the water in a river or stream and the water in sediment beneath or alongside the river. The hyporheic zone has unique properties including enhanced chemical reactions (many of which are good for reducing pollutant levels) and habitat for organisms that live nowhere else. The hyporheic zone is particularly active when water levels fluctuate in the stream or river, for instance due to storm events, because this forces water into or out of the riverbanks. This project will use field surveys to determine how much this storm-enhanced hyporheic exchange varies through a wide range of streams in the eastern USA. The field data will be combined with computer models to predict the presence and significance of this exchange in other streams. This will allow better understanding of this exchange on aquatic organisms and the transport of nutrients and pollutants. This project will also enhance several existing classes at Virginia Tech and increase student interest in pursuing careers in Science, Technology, Engineering, and Mathematics (STEM) fields which are critical for preserving and enhancing America's dynamic economy and quality of life. The project will reach out to under-represented undergraduates to improve their participation in the career-enhancing research opportunities provided by the project. Streams and rivers form a vital link among compartments of the hydrosphere. The hyporheic zone is a key interface where water exchanges between surface and subsurface, and is important for aquatic organisms, biogeochemical reactions, and contaminant attenuation. "Lung model" hyporheic exchange occurs where water enters and exits the subsurface during transient phenomena such as storms, hydropeaking, and daily snowmelt. The effect of lung model exchange on water quality has been recently shown to be substantial, yet highly dependent on exchange rate. This project will use field surveys of stream bank macropores to test whether macropores/soil pipes are common in several provinces of the eastern USA and a range of stream sizes and land uses. Field surveys will include detailed measurements of macropore geometry, connectivity, sedimentation, and plugging. These data will be used to compare the Darcy-based SUTRA model of reaction and transport to the computational fluid dynamics code Ansys CFX. The modeling will determine the relationships between controlling factors (e.g., macropore geometry, head gradients, sediment hydraulic conductivity) and the degree that macropores enhance lung model exchange. These results will then be upscaled to estimate the degree to which the presence of macropores increases the percent of stream length where lung model hyporheic exchange is significant.

溪流和河流是水循环的重要组成部分，是“万物的下游”，受大多数人类活动的影响最大。 因此，重要的是要了解溪流和河流是如何工作的，这样我们就可以解释这些好处，并预测它们如何应对城市化等趋势。潜流带是河流或溪流中的水与河流下方或沿岸沉积物中的水之间的边界。 低渗区具有独特的特性，包括增强的化学反应（其中许多有利于降低污染物水平）和其他地方没有的生物的栖息地。 当溪流或河流中的水位波动时，例如由于风暴事件，潜流区特别活跃，因为这迫使水进入或离开河岸。 该项目将使用实地调查，以确定有多少这种风暴增强的潜流交换变化，通过广泛的流在美国东部。 现场数据将与计算机模型相结合，以预测这种交换在其他河流中的存在和意义。 这将有助于更好地了解这种交换对水生生物以及营养物和污染物的迁移的影响。 该项目还将增强弗吉尼亚理工大学现有的几个课程，并提高学生在科学，技术，工程和数学（STEM）领域从事职业的兴趣，这些领域对于保护和提高美国充满活力的经济和生活质量至关重要。 该项目将接触到代表性不足的本科生，以提高他们参与该项目提供的职业发展研究机会。溪流和河流是水圈各部分之间的重要联系。 潜流带是地表和地下水交换的关键界面，对水生生物、生物地球化学反应和污染物衰减都很重要。 “肺模型”潜流交换发生在水进入和退出地下瞬态现象，如风暴，水峰，和日常融雪。 肺模型交换对水质的影响最近已被证明是实质性的，但高度依赖于交换率。 该项目将使用流银行大孔隙的实地调查，以测试大孔隙/土壤管道是否常见于美国东部的几个省份和一系列的流大小和土地使用。 现场调查将包括大孔隙几何形状、连通性、沉积和堵塞的详细测量。 这些数据将被用来比较达西为基础的SUTRA模型的反应和运输的计算流体动力学代码Ansys CFX。 建模将确定控制因素之间的关系（例如，大孔几何形状、水头梯度、沉积物水力传导率）和大孔增强肺模型交换的程度。 然后将这些结果放大，以估计大孔的存在增加肺模型低渗交换显著的流长度百分比的程度。