Quantifying Regional Fresh Submarine Groundwater Discharge With the Lumped Modeling Approach CoCa‐RFSGD

Hajati, Mithra‐Christin; Sutanudjaja, Edwin H.; Moosdorf, Nils

doi:10.1029/2018wr024248

Cited by 9 publications

(27 citation statements)

References 76 publications

(119 reference statements)

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“…However, levels of homogeneity representative for larger areas are not yet adequately defined, as is the answer to whether and how small-scale temporal variations extrapolate into a larger scale. The terrestrial component of SGD was already modeled at the regional scale (Jarsjö et al, 2008;Befus et al, 2017;Hajati et al, 2019) and global scale (Zhou et al, 2019;Luijendijk et al, 2020) using similar approaches. These models produce spatially explicit estimates of terrestrial SGD that is a necessary prerequisite for STEs.…”

Section: Hydrogeological Modelingmentioning

confidence: 99%

A State-Of-The-Art Perspective on the Characterization of Subterranean Estuaries at the Regional Scale

et al. 2021

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Subterranean estuaries the, subsurface mixing zones of terrestrial groundwater and seawater, substantially influence solute fluxes to the oceans. Solutes brought by groundwater from land and solutes brought from the sea can undergo biogeochemical reactions. These are often mediated by microbes and controlled by reactions with coastal sediments, and determine the composition of fluids discharging from STEs (i.e., submarine groundwater discharge), which may have consequences showing in coastal ecosystems. While at the local scale (meters), processes have been intensively studied, the impact of subterranean estuary processes on solute fluxes to the coastal ocean remains poorly constrained at the regional scale (kilometers). In the present communication, we review the processes that occur in STEs, focusing mainly on fluid flow and biogeochemical transformations of nitrogen, phosphorus, carbon, sulfur and trace metals. We highlight the spatio-temporal dynamics and measurable manifestations of those processes. The objective of this contribution is to provide a perspective on how tracer studies, geophysical methods, remote sensing and hydrogeological modeling could exploit such manifestations to estimate the regional-scale impact of processes in STEs on solute fluxes to the coastal ocean.

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Section: Hydrogeological Modelingmentioning

confidence: 99%

A State-Of-The-Art Perspective on the Characterization of Subterranean Estuaries at the Regional Scale

et al. 2021

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“…To quantify the impact of a land use shift from pristine forest to blueberry farming in the subtropics, we combined the catchment water balance model CoCa-RFSGD (Hajati et al, 2019) with N mass balances based on well-established N equilibrium equations and first-order kinetics. This enables us to carefully draw conclusions on atmospheric losses, while the model is only calibrated on aqueous N losses.…”

Section: Model Conceptualizationmentioning

confidence: 99%

“…The CoCa-RFSGD model (Hajati et al, 2019) is a water balance model working at catchment scale with a daily temporal resolution calculating topsoil and subsoil water content based on soil water balances. The model uses two unsaturated layers, lumped 30 cm topsoil (root zone), lumped 70 cm subsoil layer, and an aquifer layer with unspecified depth.…”

Section: Model Conceptualizationmentioning

confidence: 99%

“…Evapotranspiration was available from the MODIS product MOD16A2 (Running et al, 2017) in an 8-days resolution. Evaporation was assumed to be constant for 8 days (Hajati et al, 2019). Detailed land use maps are available for the year 2013 (OEH, 2017).…”

Section: Model Input Datamentioning

confidence: 99%

“…Here, we developed a model based on an conceptual understanding of the soil nitrogen cycle to estimate (1) catchment N surplus at data-poor regions using NO x creek water measurements only and to estimate (2) the impact of local land use changes in the subtropics. The model is an extension of the water balance model CoCa-RFSGD (Hajati et al, 2019). It was designed to simulate data-poor catchments in Indonesia because it relays on data sets, which are globally available.…”

Section: Introductionmentioning

confidence: 99%

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Modeling Catchment-Scale Nitrogen Losses Across a Land-Use Gradient in the Subtropics

et al. 2020

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Changing land use in subtropical and tropical catchments to farmland can result in higher nitrogen (N) loss to aquatic ecosystems. Here, we developed a lumped water and N balance model to estimate regional N losses to creeks at catchment scale within understudied subtropical catchments in Australia. The conceptual water balance model CoCa-RFSGD was extended by the nitrogen mass balance in top and subsoil by adding nitrogen cycle transformation estimates depending on meteorological, soil, and land-use properties. The model estimates the impact of pristine and agricultural land use on catchment-wide water quality using only low-order creek samples as water quality measurements of nitrate and nitrite (NO x ) with increased model performance with increased agricultural coverage. The model revealed that an agricultural proportion of 3% in the study site drove a 3.5-fold increase of N losses to creeks and a 6.7-fold increase of N losses to the atmosphere compared to catchments without agriculture. Agricultural land use lost 92 kg-N ha −1 , 85% of which evaded to the atmosphere and 15% was discharged via surface waters. A change from forest to cleared land may increase the total denitrification potential of a catchment. Overall, our lumped model provides a simple but effective tool to upscale local aquatic water quality measurements to the catchment scale, allowing for assessment of changing land use on aquatic N loads in areas with limited data availability.

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Physical and chemical characterization of remote coastal aquifers and submarine groundwater discharge from a glacierized watershed

Russo,

Jenckes,

Boutt

et al. 2024

Hydrological Processes

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Coastal aquifers play an important role in marine ecosystems by providing high fluxes of nutrients and solutes via submarine groundwater discharge pathways. The physical and chemical characterization of these dynamic systems is foundational to understanding the extent and magnitude of hydrogeologic processes and their subsequent contributions to the marine environment. We describe a km‐scale experimental field site located in a glaciofluvial delta entering Kachemak Bay, Alaska. Our characterization applies geophysical (ERT and HVSR), hydrogeologic (grain size analyses, slug tests and tidal response analyses) and geochemical (major ions and stable water isotopes) methods to describe the complexity of coastal aquifers in proglacial environments currently experiencing rapid transformations. The hydrogeologic and geophysical techniques revealed thick (20–84 m) sediments dominated by sands and gravels and delineated zones of freshwater, brackish water and saltwater at both high and low tides within the subterranean estuary. Estimates of hydraulic conductivities via multiple approaches ranged from 2 to 250 m d−1, with means across the four methods within the same order of magnitude. Tidal response analyses highlighted a coastal aquifer in strong connection with the sea as evidenced by clear spring‐ and neap‐tidal signals within a proximal piezometric hydrograph. Geochemical sampling revealed coastal groundwaters as substantially enriched in solutes compared to proximal river samples with limited variability across seasons. A clear connection between the Wosnesenski River and the adjacent aquifer was also observed, with concentrated recharge from the river corridor during the meltwater season. This combination of approaches provides the basis for a conceptual model for coastal aquifer systems within the Gulf of Alaska and an upscaled mean daily yield of freshwater and solutes from the delta subsurface. Our findings are critical for subsequent numerical simulations of groundwater flow, tidal pumping and chemical reactions and transport in these understudied environments. This approach may be applied for low‐cost, large‐scale hydrogeologic investigations in coastal areas and may be particularly useful for remote sites where access and mobility are challenging.

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Quantifying Regional Fresh Submarine Groundwater Discharge With the Lumped Modeling Approach CoCa‐RFSGD

Cited by 9 publications

References 76 publications

A State-Of-The-Art Perspective on the Characterization of Subterranean Estuaries at the Regional Scale

A State-Of-The-Art Perspective on the Characterization of Subterranean Estuaries at the Regional Scale

Modeling Catchment-Scale Nitrogen Losses Across a Land-Use Gradient in the Subtropics

Physical and chemical characterization of remote coastal aquifers and submarine groundwater discharge from a glacierized watershed

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