RAPID: The effects of extreme drought on sediment transport and deposition in water-supply reservoirs

RAPID：极端干旱对供水水库泥沙输送和沉积的影响

• 批准号: 2203159
• 负责人: Irina Overeem
• 金额: $ 5万
• 依托单位: University of Colorado at Boulder
• 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: 2021-12-15 至 2023-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2203159&HistoricalAwards=false
• 关键词: RAPID; effects; extreme; drought; sediment

The southwestern U.S. is experiencing an extreme drought that is reducing flow in river systems and producing record low levels in water-supply reservoirs. For example, the Elephant Butte Reservoir on the Rio Grande River in New Mexico was only 5.6% full as of October, exposing a large wedge of sediment that has extended an additional 1 km into the reservoir during the summer of 2021. During the drought, flash floods are the principal means by which water enters the reservoir. Flash floods bring sediment-laden flows that can accumulate in the reservoir and reduce the capacity further. This project will collect time-sensitive data to assess impacts of the extreme drought on water budgets, river sediment transport, and reservoir sedimentation. The project will train one graduate student in the integration of field, laboratory methods, and numerical modeling. The research has applications to similar processes occurring in coastal regions and will help in making complex decisions on water release and management of wetlands in western river corridors. The severe drought in the Rio Grande River basin has caused a delta to emerge at the entrance into the Elephant Butte Reservoir. During the drought year of 2021, spring snowmelt was subdued, and flash floods from storm events became the predominant mechanism for sediment transport into the reservoir. These flash flood-derived sediments accumulate upon entering reservoirs to form a lacustrine delta, which unlike marine deltas, typically experience hyperpycnal flows. Initial research during a monsoon-driven flash flood in July 2021 indicate that heightened sediment and organic carbon transport affected the geomorphology and ecology during the event. This RAPID project will identify the mechanisms driving flash flood sediment transport and morphodynamics in arid fluvio-deltaic systems and determine how extreme drought amplifies these processes. The research will also numerically model the Elephant Butte Reservoir deltaic system to evaluate geomorphic changes in the subaqueous delta driven by highly sediment-laden flash floods, which will also inform the carbon sequestration potential of such rapidly prograding deltas. The proposed research involves two field campaigns in the winter and spring of 2022 to collect water and bed material samples, channel geometry, velocity, and water level measurements, images of the delta front, and casts of a conductivity, temperature, and depth sensor. The data will be incorporated into the hydrodynamics and sediment transport model Delft3D to simulate sediment transport and deposition processes during a flash flood at high resolution, which has never been done in a reservoir setting.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.

美国西南部正在经历极端干旱，河流系统流量减少，供水水库水位创历史新低。例如，截至 10 月，新墨西哥州格兰德河上的象山水库蓄水量仅为 5.6%，暴露出一大块沉积物，这些沉积物在 2021 年夏季又向水库延伸了 1 公里。在干旱期间，山洪爆发是水进入水库的主要方式。山洪暴发带来的泥沙流可能会积聚在水库中，进一步降低水库容量。该项目将收集时间敏感的数据，以评估极端干旱对水预算、河流泥沙输送和水库沉积的影响。 该项目将培训一名研究生，将现场、实验室方法和数值建模相结合。该研究可应用于沿海地区发生的类似过程，并将有助于对西部河流走廊湿地的放水和管理做出复杂的决策。里奥格兰德河流域的严重干旱导致象山水库入口处出现了一个三角洲。 2021年干旱年，春季融雪量减弱，风暴事件引发的山洪成为泥沙输入水库的主要机制。这些由山洪爆发产生的沉积物在进入水库后堆积，形成湖泊三角洲，与海洋三角洲不同，该三角洲通常经历异重流。 2021 年 7 月季风驱动的山洪爆发期间的初步研究表明，沉积物和有机碳迁移的增加影响了该事件期间的地貌和生态。该 RAPID 项目将确定驱动干旱河流三角洲系统中山洪沉积物迁移和形态动力学的机制，并确定极端干旱如何放大这些过程。该研究还将对象山水库三角洲系统进行数值模拟，以评估由高度沉积物山洪驱动的水下三角洲的地貌变化，这也将有助于了解此类快速进积三角洲的碳封存潜力。拟议的研究涉及 2022 年冬季和春季的两次实地活动，以收集水和底质样本、河道几何形状、速度和水位测量值、三角洲前缘图像以及电导率、温度和深度传感器的模型。这些数据将被纳入水动力和泥沙运移模型 Delft3D，以高分辨率模拟山洪期间的泥沙运移和沉积过程，这在水库环境中从未完成过。该奖项反映了 NSF 的法定使命，并被认为是值得的通过使用基金会的智力优势和更广泛的影响审查标准进行评估来提供支持。