Surface water‐groundwater connectivity in deltaic distributary channel networks

Sawyer, Audrey H.; Edmonds, Douglas A.; Knights, Deon

doi:10.1002/2015gl066156

Cited by 35 publications

(32 citation statements)

References 80 publications

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“…Finally, we want to emphasize the broad applicability of this framework to diverse fields in the geosciences where multiprocess multiscale interactions dictate the overall system behavior. Examples include flux transport taking into account surface-subsurface exchange (Sawyer et al, 2015), integrated wetland and river systems (Hansen et al, 2018), interaction types among species in ecological systems (Pilosof et al, 2017), and climate networks (Donges et al, 2011).…”

Section: 1029/2018gl078355mentioning

confidence: 99%

Multiplex Networks: A Framework for Studying Multiprocess Multiscale Connectivity Via Coupled‐Network Theory With an Application to River Deltas

Tejedor

Longjas

Passalacqua

et al. 2018

Geophysical Research Letters

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Transport of water, nutrients, or energy fluxes in many natural or coupled human natural systems occurs along different pathways that often have a wide range of transport timescales and might exchange fluxes with each other dynamically. Although network approaches have been proposed for studying connectivity and transport properties on single-layer networks, theories considering interacting networks are lacking. We present a general framework for transport on multiscale coupled-connectivity systems, via multilayer networks which conceptualize the system as a set of interacting networks, each arranged in a separate layer, and with interactions across layers acknowledged by interlayer links. We illustrate this framework by examining transport in river deltas as a dynamic interaction of flow within river channels and overland flow on the islands, when controlled by the flooding level. We show the potential of the framework to answer quantitative questions related to the characteristic timescale of response in the system. Plain Language SummaryThe physical processes that shape landscapes leave behind patterns of connectivity along which fluxes occur via a multitude of processes, for example, flow through channels, subsurface or overland flow. The connectivity imposed by those processes (e.g., channel networks) exerts a significant control on the evolution and form of the underlying systems. We introduce a framework based on coupled networks, Multiplex, that allows to quantify the connectivity properties emerging from the simultaneous action of different processes, enabling thus to assess the overall system properties and dynamics. We illustrate this framework by examining the case of river deltas, where intermittent flooding and exchange of water, sediment, and nutrients between the channels and the islands maintains the delta top by trapping sediment, stabilizing banks, and enriching rivers with carbon and nutrients. By describing the delta system as a Multiplex-integrating the connectivity imposed by confined (in the channel network) and overland (on the islands) flows as well as the interactions (flux exchange) between them-we show the emergence of system transport properties and dynamics not foreseen by analyzing each process separately, and therefore revealing key information essential to predict the system response under changing forcing.

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Section: 1029/2018gl078355mentioning

confidence: 99%

Multiplex Networks: A Framework for Studying Multiprocess Multiscale Connectivity Via Coupled‐Network Theory With an Application to River Deltas

Tejedor

Longjas

Passalacqua

et al. 2018

Geophysical Research Letters

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“…However, in systems subject to flow direction reversal across the boundary (e.g., due to a flood tide), the total time a water parcel spends in the domain can be underestimated by the residence time (Monsen et al, ), leading to the adoption of the exposure time, or the cumulative amount of time a water parcel spends in the control volume regardless of its excursions outside the domain (e.g., de Brauwere et al, ; de Brye et al, ; Delhez, ; Monsen et al, ; Viero & Defina, ). Despite the environmental importance of river deltas, the study of water transport time scales in coastal river deltas is relatively nascent (Hiatt & Passalacqua, ; Sawyer et al, ; Sendrowski & Passalacqua, ). The goal of this paper is to quantify controls on the exposure time distribution (ETD) in a coastal river delta.…”

Section: Introductionmentioning

confidence: 99%

Channel‐Island Connectivity Affects Water Exposure Time Distributions in a Coastal River Delta

Hiatt

Castañeda‐Moya

Twilley

et al. 2018

Water Resources Research

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The exposure time is a water transport time scale defined as the cumulative amount of time a water parcel spends in the domain of interest regardless of the number of excursions from the domain. Transport time scales are often used to characterize the nutrient removal potential of aquatic systems, but exposure time distribution estimates are scarce for deltaic systems. Here we analyze the controls on exposure time distributions using a hydrodynamic model in two domains: the Wax Lake delta in Louisiana, USA, and an idealized channel‐island complex. In particular, we study the effects of river discharge, vegetation, network geometry, and tides and use a simple model for the fractional removal of nitrate. In both domains, we find that channel‐island hydrological connectivity significantly affects exposure time distributions and nitrate removal. The relative contributions of the island and channel portions of the delta to the overall exposure time distribution are controlled by island vegetation roughness and network geometry. Tides have a limited effect on the system's exposure time distribution but can introduce significant spatial variability in local exposure times. The median exposure time for the WLD model is 10 h under the conditions tested and water transport within the islands contributes to 37–50% of the network‐scale exposure time distribution and 52–73% of the modeled nitrate removal, indicating that islands may account for the majority of nitrate removal in river deltas.

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“…Sawyer et al . [] found that mesoscale landforms are one of the major controlling factors in surface water‐groundwater exchange and solute retention. Macrotopography refers to the overall topographic gradient.…”

Section: Introductionmentioning

confidence: 99%

Impact of topography on groundwater salinization due to ocean surge inundation

Yang

Graf

et al. 2016

Water Resources Research

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Sea‐level rise and increases in the frequency and intensity of ocean surges caused by climate change are likely to exacerbate adverse effects on low‐lying coastal areas. The landward flow of water during ocean surges introduces salt to surficial coastal aquifers and threatens groundwater resources. Coastal topographic features (e.g., ponds, dunes, barrier islands, and channels) likely have a strong impact on overwash and salinization processes, but are generally highly simplified in modeling studies. To understand topographic impacts on groundwater salinization, we modeled a theoretical overwash event and variable‐density groundwater flow and salt transport in 3‐D using the fully coupled surface and subsurface numerical simulator, HydroGeoSphere. The model simulates the coastal aquifer as an integrated system considering overland flow, coupled surface and subsurface exchange, variably saturated flow, and variable‐density groundwater flow. To represent various coastal landscape types, we simulated both synthetic fields and real‐world coastal topography from Delaware, USA. The groundwater salinization assessment suggested that the topographic connectivity promoting overland flow controls the volume of aquifer that is salinized. In contrast, the amount of water that can be stored in surface depressions determines the amount of seawater that infiltrates the subsurface and the time for seawater to flush from the aquifer. Our study suggests that topography has a significant impact on groundwater salinization due to ocean surge overwash, with important implications for coastal land management and groundwater vulnerability assessment.

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Surface water‐groundwater connectivity in deltaic distributary channel networks

Cited by 35 publications

References 80 publications

Multiplex Networks: A Framework for Studying Multiprocess Multiscale Connectivity Via Coupled‐Network Theory With an Application to River Deltas

Multiplex Networks: A Framework for Studying Multiprocess Multiscale Connectivity Via Coupled‐Network Theory With an Application to River Deltas

Channel‐Island Connectivity Affects Water Exposure Time Distributions in a Coastal River Delta

Impact of topography on groundwater salinization due to ocean surge inundation

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