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RAPID: Draining the landscape: Will the drop in stream and groundwater levels following dam removal increase the leaching/leakage of nitrogen (N) from riparian zones?

快速：景观排水：大坝拆除后溪流和地下水位的下降是否会增加河岸区域氮 (N) 的淋滤/泄漏？

基本信息

批准号：
1901787
负责人：
Shreeram Inamdar
金额：
$ 4.99万
依托单位：
University of Delaware
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-11-01 至 2020-10-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1901787&HistoricalAwards=false
关键词：
RAPID Draining landscape Will drop

项目摘要

A large number of dams are currently being removed across the U.S. and at an accelerating pace. Most of the dam removals are driven by the need to increase public safety, reduce owner liability, and improve fish/aquatic habitat. However, little attention is being paid to how dam removals could influence water quality. Generally, dams slow down the flow of water and simultaneously raise the level of water in the stream and in the stream-side areas known as riparian areas. Unintentionally, this provides a valuable benefit: wet soils rich in carbon act as important filters for nitrogen, a key pollutant in waterways. This natural filtering service reduces stream water nitrogen concentrations and improves water quality. Dam removals could undermine this valuable service and potentially increase nitrogen in streams. This study will quantify how dam removal alters the capacity of riparian soils in filtering nitrogen. Results will be conveyed to landowners and natural resource agencies which will position them to make informed decisions on dam removals and better manage our watersheds. The study will provide a valuable opportunity for education and professional development for undergraduate and graduate students. In addition to presentations at professional conferences and meetings, project results will be disseminated to broader, non-academic audiences through talks at community Science Cafes.Near-surface groundwater and wet soil conditions in riparian zones, particularly upstream of dams, enhance denitrification in soils - a key mechanism by which riparian zones filter and remove nitrogen (N) from soils and act as hot spots for nitrogen buffering. Dam removals can lower groundwater levels, expose and dry riparian soils, and result in loss of valuable denitrification ecosystem services. Furthermore, drying of soils could enhance mineralization and nitrification, processes that release soil N and increase water pollution. This could result in riparian zones switching from watershed N sinks to sources. This hypothesis (increasing soil N leakage following dam removal) will be tested at the Chickies Creek site in Pennsylvania where the Krady Mill dam was recently removed. Stream water and ground waters at two riparian transects will be monitored and sampled weekly to study changes in concentration of nitrogen species. Riparian soil samples along the transects and at various soil depths will be collected to measure changes in soil N concentrations and the rates of mineralization, nitrification and denitrification. Measured process rates along with areal extent of the drained soils will be used to estimate/predict the N leakage (kg per unit stream length) following dam removal. Considering increasing dam removals across the U.S., results from this study will provide novel insights critical for watershed management and assessing the benefits and drawbacks of dam removal.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.

目前，美国各地正在拆除大量大坝，而且速度正在加快。大多数大坝拆除是出于增加公共安全、减少所有者责任和改善鱼类/水生生境的需要。然而，很少有人关注大坝拆除如何影响水质。一般来说，水坝减缓水流速度，同时提高河流和河岸地区的水位。无意中，这提供了一个有价值的好处：富含碳的潮湿土壤作为氮的重要过滤器，氮是水道中的关键污染物。这种自然过滤服务降低了溪流中的氮浓度并改善了水质。大坝的拆除可能会破坏这种宝贵的服务，并可能增加河流中的氮。这项研究将量化大坝拆除如何改变河岸土壤过滤氮的能力。结果将传达给土地所有者和自然资源机构，使他们能够就大坝拆除作出明智的决定，并更好地管理我们的流域。这项研究将为本科生和研究生的教育和专业发展提供宝贵的机会。除了在专业会议上进行介绍外，项目成果还将通过在社区科学咖啡馆的讲座传播给更广泛的非学术受众。河岸带（特别是水坝上游）的近地表地下水和湿润土壤条件增强了土壤中的反硝化作用--这是河岸带过滤和去除土壤中氮（N）的一种关键机制，并成为氮缓冲的热点。拆除大坝会降低地下水位，暴露和干燥河岸土壤，并导致宝贵的反硝化生态系统服务的损失。此外，土壤干燥会增强矿化和硝化作用，这是释放土壤氮和增加水污染的过程。这可能会导致河岸带切换流域N汇源。这一假设（大坝拆除后土壤氮泄漏增加）将在宾夕法尼亚州的Chickies Creek现场进行测试，该现场最近拆除了Krady Mill大坝。将监测两个河岸样带的河水和地下沃茨，并每周取样，以研究氮物质浓度的变化。将采集沿着样带和不同土壤深度的河岸土壤样品，以测量土壤氮浓度的变化以及矿化、硝化和反硝化速率。测量的过程速率沿着排水土壤的面积范围将用于估计/预测大坝拆除后的氮泄漏（kg/单位河流长度）。考虑到美国各地越来越多的大坝拆除，这项研究的结果将为流域管理和评估大坝拆除的利弊提供新的见解。2该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。