Collaborative Research: Oligohaline dispersion: transport processes at the estuary-tidal river transition

合作研究：寡盐分散：河口-潮汐河过渡过程中的传输过程

• 批准号: 2318998
• 负责人: Robert Chant
• 金额: $ 58.63万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2318998&HistoricalAwards=false
• 关键词: Collaborative; Research; Oligohaline; dispersion; transport

Transport processes controlling the salinity distribution in an estuary vary dynamically with the river discharge, tides, and meteorological events. Most of our understanding of the transport processes is based on studies of the central reach of estuaries. The upper reach near the landward limit of the salt intrusion, has distinct physical characteristics that make transport processes different from the central reach. This project will combine in-situ and shipboard observations, dye release studies, and realistic high-resolution modeling to quantify tidal dispersion in the upper reach of the Delaware River estuary. Analysis of the observations and modeling will be closely linked through direct comparisons, and together they will be used to quantify dispersion rates and identify the mechanisms. Bathymetric features like channel constrictions and bends as well as anthropogenic modifications like piers and dredged channels are expected to be particularly important to creating salinity and velocity anomalies that lead to net landward transport. The Delaware is representative of many estuaries around the world where water supplies drawn from tidal rivers are increasingly threatened by landward shifts in the oligohaline reach with sea level rise, changing precipitation, and dredging. Specifically, drinking water intakes for the Philadelphia Water District (PWD) are located just upstream of the study region, and the Delaware River Basin Commission (DRBC) controls river flow conditions to regulate the salt intrusion and protect the water supply for millions. This project will build on established relationships between the PIs and colleagues at both PWD and DRBC to identify knowledge gaps and link study findings to management decisions. The PIs will also contribute to a series of workshops bringing together scientists and water resources managers to assess threats to water supplies by salt intrusion globally. The project will support a graduate student at Rutgers who will be involved in all aspects of the study, including observations, modeling, and outreach.The oligohaline reach (0.5-5 psu) is an important transition zone for many ecological and biogeochemical processes, and yet few studies have examined the physical mechanisms of transport. Several key characteristics distinguish the oligohaline from the central estuary. In the asymptote to freshwater, the along-estuary salinity gradient decreases and estuarine exchange flow weakens. Stratification also decreases, reducing the steady salt flux and increasing mixing, which reduces oscillatory shear dispersion. Channel narrowing affects lateral exchange and trapping, particularly in urbanized estuaries with shoreline modification. This project uses multiple, complementary approaches to quantify transport processes in this region. Observations during low river discharge will capture the spatial and temporal evolution of salinity with tidal and meteorological forcing, and dye releases will directly quantify dispersion at the scale of topographic features. Modeling will use a nested-grid approach to represent the bathymetric features driving dispersion, along with a novel analysis approach to isolate sources of non-local salt flux, as put forth by Dronkers and van de Kreeke (1986). A process-based understanding of transport in the oligohaline reach is critical to understanding how conditions there will evolve with climate change and continued development.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.

控制河口盐度分布的输送过程随着河流流量、潮汐和气象事件而动态变化。我们对运输过程的大部分理解都是基于对河口中央河段的研究。上游靠近盐侵入陆界的边界，具有明显的物理特征，使得输送过程与中部河段不同。该项目将结合现场和船上观测、染料释放研究和现实的高分辨率建模，以量化特拉华河河口上游的潮汐扩散。对观测结果的分析和建模将通过直接比较紧密联系起来，它们将一起用于量化离散率并确定其机制。航道收缩和弯曲等测深特征以及码头和疏浚航道等人为改造预计对于产生导致净向陆运输的盐度和速度异常特别重要。特拉华河是世界上许多河口的代表，随着海平面上升、降水量变化和疏浚，寡盐河段向陆地移动，从潮汐河流汲取的水源日益受到威胁。具体而言，费城水区 (PWD) 的饮用水取水口位于研究区域的上游，特拉华河流域委员会 (DRBC) 控制河流水流状况，以调节盐分入侵并保护数百万人的供水。该项目将建立在 PWD 和 DRBC 的 PI 与同事之间已建立的关系的基础上，以确定知识差距并将研究结果与管理决策联系起来。首席研究员还将为一系列研讨会做出贡献，这些研讨会将科学家和水资源管理者聚集在一起，评估全球盐分入侵对供水的威胁。该项目将支持罗格斯大学的一名研究生，他将参与该研究的各个方面，包括观察、建模和推广。寡盐范围（0.5-5 psu）是许多生态和生物地球化学过程的重要过渡区，并且然而很少有研究探讨运输的物理机制。寡盐与中央河口有几个关键特征不同。在淡水渐近线，沿河口盐度梯度减小，河口交换流减弱。分层也会减少，从而减少稳定的盐通量并增加混合，从而减少振荡剪切分散。河道变窄会影响横向交换和捕获，特别是在海岸线改变的城市化河口。该项目使用多种互补的方法来量化该地区的运输过程。河流流量低时的观测将捕捉盐度随潮汐和气象强迫的空间和时间演变，染料释放将直接量化地形特征尺度的分散。建模将使用嵌套网格方法来表示驱动扩散的测深特征，以及隔离非局部盐通量来源的新颖分析方法，如 Dronkers 和 van de Kreeke (1986) 提出的。基于过程的对寡盐范围内运输的理解对于理解那里的条件将如何随着气候变化和持续发展而演变至关重要。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响进行评估，被认为值得支持审查标准。