Groundwater age from multi-level bores: What it can tell about the aquifers

2021 ◽  
Author(s):  
Uwe Morgenstern ◽  
Zara Rawlinson
Keyword(s):  
Groundwater Flow ◽  
Groundwater Recharge ◽  
Sea Level ◽  
Preferential Flow ◽  
Groundwater Age ◽  
Geological Processes ◽  
Recharge Sources ◽  
Transient Electromagnetic ◽  
Geophysical Surveys ◽  
Multi Level

<p>Geologic data to provide information on the functioning of aquifers is often scars. For the aquifers underlying the Heretaunga Plains, Hawkes Bay, one of New Zealand’s most important groundwater systems, we used groundwater age (tritium, SF6, 14C) to inform the geologic model and to provide information on groundwater flow through alternating strata of permeable river gravel beds and fine impermeable beds that form an interconnected unconfined–confined aquifer system with complex groundwater flow processes.</p><p>The aquifers are a result of geological processes responding to climate change cycles from cold glacial when sea level was more than 100m below present sea level, to warm interglacial periods with sea level similar to present day. Glacial climate strata are river gravel, sand and silt deposits and include the artesian aquifers. The interglacial strata form the aquicludes and are marine sand, silt, and clay deposits with interbedded estuarine, swamp and coastal fluvial silt, clay, peat and gravel deposits.</p><p>We have re-visited tracer data sampled during the drilling of multi-level observation well in the early 1990s, and collected new samples from these multi-level bores in order to understand in 3D the groundwater recharge sources, groundwater recharge and flow rates, connection to the rivers, and potential groundwater discharge out to sea. Consistently young water (c. 25 years) at depth greater than 100m indicates preferential flow paths, likely related to paleo-river channels. The flow pattern obtained from the water tracer data improves the geologic information from the drill-holes, and fits with information from recent airborne transient electromagnetic (SkyTEM) geophysical surveys.</p>

scholarly journals Transboundary geophysical mapping of geological elements and salinity distribution critical for the assessment of future sea water intrusion in response to sea level rise

2012 ◽  
Vol 9 (3) ◽  
pp. 2629-2674 ◽  
Author(s):  
F. Jørgensen ◽  
W. Scheer ◽  
S. Thomsen ◽  
T. O. Sonnenborg ◽  
K. Hinsby ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
Sea Level Rise ◽  
Sea Level ◽  
Preferential Flow ◽  
Sea Water ◽  
Saline Water ◽  
Seismic Survey ◽  
Salinity Distribution ◽  
Chemical Status ◽  
Transient Electromagnetic

Abstract. Geophysical techniques are increasingly used as tools for characterising the subsurface and they are generally required to develop subsurface models that properly delineate the distribution of aquifers and aquitards, salt/freshwater interfaces and geological structures that affect groundwater flow. In a study area covering 730 km2 across the border between Germany and Denmark a combination of an airborne transient electromagnetic survey (performed with the SkyTEM system), a high-resolution seismic survey and borehole logging has been used in an integrated mapping of important geological, physical and chemical features of the subsurface. The spacing between flight lines is 200–250 m giving a total of about 3200 line km. About 38 km of seismic lines have been collected. Faults bordering a graben structure, deep and shallow buried tunnel valleys, glaciotectonic thrust complexes, marine clay units, and sand aquifers are all examples of geological elements mapped by the geophysical data that control groundwater flow and to some extent hydrochemistry. Additionally, the data provide an excellent picture of the salinity distribution in the area thus providing important information on the fresh-saltwater boundary and the chemical status of groundwater. Although, the westernmost part of the study area along the North Sea coast is saturated with saline water and the TEM data therefore is strongly influenced by the increased electrical conductivity here, buried valleys and other geological elements are still revealed. The salinity distribution indicates preferential flow paths through and along specific geological elements within the area. The effects of future sea level rise on the groundwater system and chemical status are discussed with special emphasis on the importance of knowing the existence, distribution and geometry of the mapped geological elements, and assessing their control on the groundwater salinity distribution.

scholarly journals Transboundary geophysical mapping of geological elements and salinity distribution critical for the assessment of future sea water intrusion in response to sea level rise

2012 ◽  
Vol 16 (7) ◽  
pp. 1845-1862 ◽  
Author(s):  
F. Jørgensen ◽  
W. Scheer ◽  
S. Thomsen ◽  
T. O. Sonnenborg ◽  
K. Hinsby ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
Sea Level Rise ◽  
Sea Level ◽  
Preferential Flow ◽  
Sea Water ◽  
Saline Water ◽  
Seismic Survey ◽  
Salinity Distribution ◽  
Geological Structures ◽  
The North

Abstract. Geophysical techniques are increasingly being used as tools for characterising the subsurface, and they are generally required to develop subsurface models that properly delineate the distribution of aquifers and aquitards, salt/freshwater interfaces, and geological structures that affect groundwater flow. In a study area covering 730 km2 across the border between Germany and Denmark, a combination of an airborne electromagnetic survey (performed with the SkyTEM system), a high-resolution seismic survey and borehole logging has been used in an integrated mapping of important geological, physical and chemical features of the subsurface. The spacing between flight lines is 200–250 m which gives a total of about 3200 line km. About 38 km of seismic lines have been collected. Faults bordering a graben structure, buried tunnel valleys, glaciotectonic thrust complexes, marine clay units, and sand aquifers are all examples of geological structures mapped by the geophysical data that control groundwater flow and to some extent hydrochemistry. Additionally, the data provide an excellent picture of the salinity distribution in the area and thus provide important information on the salt/freshwater boundary and the chemical status of groundwater. Although the westernmost part of the study area along the North Sea coast is saturated with saline water and the TEM data therefore are strongly influenced by the increased electrical conductivity there, buried valleys and other geological elements are still revealed. The mapped salinity distribution indicates preferential flow paths through and along specific geological structures within the area. The effects of a future sea level rise on the groundwater system and groundwater chemistry are discussed with special emphasis on the importance of knowing the existence, distribution and geometry of the mapped geological elements, and their control on the groundwater salinity distribution is assessed.

scholarly journals A multi-environmental tracer study to determine groundwater residence times and recharge in a structurally complex multi-aquifer system

2020 ◽  
Vol 24 (1) ◽  
pp. 249-267 ◽  
Author(s):  
Cornelia Wilske ◽  
Axel Suckow ◽  
Ulf Mallast ◽  
Christiane Meier ◽  
Silke Merchel ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
Groundwater Recharge ◽  
Groundwater Age ◽  
Age Distribution ◽  
Dead Sea ◽  
Artificial Sweetener ◽  
Environmental Tracers ◽  
Jordan Valley ◽  
Aquifer System ◽  
Lumped Parameter

Abstract. Despite being the main drinking water resource for over 5 million people, the water balance of the Eastern Mountain Aquifer system on the western side of the Dead Sea is poorly understood. The regional aquifer consists of fractured and karstified limestone – aquifers of Cretaceous age, and it can be separated into a Cenomanian aquifer (upper aquifer) and Albian aquifer (lower aquifer). Both aquifers are exposed along the mountain ridge around Jerusalem, which is the main recharge area. From here, the recharged groundwater flows in a highly karstified aquifer system towards the east and discharges in springs in the lower Jordan Valley and Dead Sea region. We investigated the Eastern Mountain Aquifer system for groundwater flow, groundwater age and potential mixtures, and groundwater recharge. We combined 36Cl ∕ Cl, tritium, and the anthropogenic gases SF6, CFC-12 (chlorofluorocarbon) and CFC-11, while using CFC-113 as “dating” tracers to estimate the young water components inside the Eastern Mountain Aquifer system. By application of lumped parameter models, we verified young groundwater components from the last 10 to 30 years and an admixture of a groundwater component older than about 70 years. Concentrations of nitrate, simazine (pesticide), acesulfame K (ACE-K; artificial sweetener) and naproxen (NAP; drug) in the groundwater were further indications of infiltration during the last 30 years. The combination of multiple environmental tracers and lumped parameter modelling helped to understand the groundwater age distribution and to estimate recharge despite scarce data in this very complex hydrogeological setting. Our groundwater recharge rates support groundwater management of this politically difficult area and can be used to inform and calibrate ongoing groundwater flow models.

scholarly journals A multi-environmental tracer study to determine groundwater residence times and recharge in a structurally complex multi-aquifer system

2019 ◽  
Author(s):  
Cornelia Wilske ◽  
Axel Suckow ◽  
Ulf Mallast ◽  
Christiane Meier ◽  
Silke Merchel ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
Groundwater Recharge ◽  
Groundwater Age ◽  
Age Distribution ◽  
Dead Sea ◽  
Artificial Sweetener ◽  
Environmental Tracers ◽  
Jordan Valley ◽  
Aquifer System ◽  
Lumped Parameter

Abstract. Despite being the main drinking water resource for over five million people, the water balance of the Eastern Mountain Aquifer system on the western side of the Dead Sea is poorly understood. The regional aquifer consists of fractured and karstified limestone – aquifers of Cretaceous age and can be separated in Cenomanian aquifer (upper aquifer) and Albian aquifer (lower aquifer). Both aquifers are exposed along the mountain ridge around Jerusalem, which is the main recharge area. From here, the recharged groundwater flows in a highly karstified aquifer system towards the east, to discharge in springs in the Lower Jordan Valley and Dead Sea region. We investigated the Eastern Mountain Aquifer system on groundwater flow, groundwater age and potential mixtures, and groundwater recharge. We combined 36Cl/Cl, tritium and the anthropogenic gases SF6, CFC-12 and CFC-11, CFC-113 as dating tracers to estimate the young water components inside the Eastern Mountain Aquifer system. By application of lumped parameter models, we verified young groundwater components from the last 10 to 30 years and an admixture of a groundwater component older than about 70 years. Concentrations of nitrate, Simazine® (Pesticide), Acesulfame K® (artificial sweetener) and Naproxen® (drug) in the groundwater were further indications of infiltration during the last 30 years. The combination of multiple environmental tracers and lumped parameter modelling helped to understand the groundwater age distribution and to estimate recharge despite scarce data in this very complex hydrogeological setting. Our groundwater recharge rates support groundwater management of this politically difficult area and can be used to inform and calibrate ongoing groundwater flow models.

scholarly journals Conceptual and Mathematical Modeling of a Coastal Aquifer in Eastern Delta of R. Nestos (N. Greece)

Hydrology ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 23
Author(s):  
Ioannis Gkiougkis ◽  
Christos Pouliaris ◽  
Fotios-Konstantinos Pliakas ◽  
Ioannis Diamantis ◽  
Andreas Kallioras
Keyword(s):  
Mathematical Modeling ◽  
Groundwater Flow ◽  
Coastal Aquifer ◽  
Flow Model ◽  
Meteorological Data ◽  
Field Measurements ◽  
Groundwater Flow Model ◽  
Aquifer System ◽  
Geophysical Surveys ◽  
The Mathematical Model

In this paper, the development of the conceptual and groundwater flow model for the coastal aquifer system of the alluvial plain of River Nestos (N. Greece), that suffers from seawater intrusion due to over-pumping for irrigation, is analyzed. The study area is a typical semi-arid hydrogeologic environment, composed of a multi-layer granular aquifers that covers the eastern coastal delta system of R. Nestos. This study demonstrates the results of a series of field measurements (such as geophysical surveys, hydrochemical and isotopical measurements, hydro-meteorological data, land use, irrigation schemes) that were conducted during the period 2009 to 2014. The synthesis of the above resulted in the development of the conceptual model for this aquifer system, that formed the basis for the application of the mathematical model for simulating groundwater flow. The mathematical modeling was achieved using the finite difference method after the application of the USGS code MODFLOW-2005.

scholarly journals Data for the subsurface characterization of Pahang River Basin with the application of Transient Electromagnetic geophysical surveys

Data in Brief ◽  
2020 ◽  
Vol 30 ◽  
pp. 105491 ◽  
Author(s):  
Hariri Arifin ◽  
John Kayode ◽  
Khairul Arifin ◽  
Zuhar Zahir ◽  
Manan Abdullah ◽  
...  
Keyword(s):  
River Basin ◽  
Subsurface Characterization ◽  
Transient Electromagnetic ◽  
Geophysical Surveys

scholarly journals Effects of preferential flow on snowmelt partitioning and groundwater recharge in frozen soils

2019 ◽  
Vol 23 (12) ◽  
pp. 5017-5031 ◽  
Author(s):  
Aaron A. Mohammed ◽  
Igor Pavlovskii ◽  
Edwin E. Cey ◽  
Masaki Hayashi
Keyword(s):  
Soil Moisture ◽  
Groundwater Recharge ◽  
Preferential Flow ◽  
Frozen Soil ◽  
Time Lags ◽  
Runoff Generation ◽  
Frozen Ground ◽  
Soil Matrix ◽  
Frozen Soils ◽  
Flow Through

Abstract. Snowmelt is a major source of groundwater recharge in cold regions. Throughout many landscapes snowmelt occurs when the ground is still frozen; thus frozen soil processes play an important role in snowmelt routing, and, by extension, the timing and magnitude of recharge. This study investigated the vadose zone dynamics governing snowmelt infiltration and groundwater recharge at three grassland sites in the Canadian Prairies over the winter and spring of 2017. The region is characterized by numerous topographic depressions where the ponding of snowmelt runoff results in focused infiltration and recharge. Water balance estimates showed infiltration was the dominant sink (35 %–85 %) of snowmelt under uplands (i.e. areas outside of depressions), even when the ground was frozen, with soil moisture responses indicating flow through the frozen layer. The refreezing of infiltrated meltwater during winter melt events enhanced runoff generation in subsequent melt events. At one site, time lags of up to 3 d between snow cover depletion on uplands and ponding in depressions demonstrated the role of a shallow subsurface transmission pathway or interflow through frozen soil in routing snowmelt from uplands to depressions. At all sites, depression-focused infiltration and recharge began before complete ground thaw and a significant portion (45 %–100 %) occurred while the ground was partially frozen. Relatively rapid infiltration rates and non-sequential soil moisture and groundwater responses, observed prior to ground thaw, indicated preferential flow through frozen soils. The preferential flow dynamics are attributed to macropore networks within the grassland soils, which allow infiltrated meltwater to bypass portions of the frozen soil matrix and facilitate both the lateral transport of meltwater between topographic positions and groundwater recharge through frozen ground. Both of these flow paths may facilitate preferential mass transport to groundwater.

Contrasting facies patterns between river-dominated and symmetrical wave-dominated delta deposits

2021 ◽  
Vol 91 (3) ◽  
pp. 262-295
Author(s):  
BRIAN J. WILLIS ◽  
TAO SUN ◽  
R. BRUCE AINSWORTH
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Preferential Flow ◽  
Return Flow ◽  
Lateral Migration ◽  
Littoral Drift ◽  
Delta Front ◽  
Reference Case ◽  
Depositional Processes ◽  
The Impact

Abstract Process-physics-based, coupled hydrodynamic–morphodynamic delta models are constructed to understand preserved facies heterogeneities that can influence subsurface fluid flow. Two deltaic systems are compared that differ only in the presence of waves: one river dominated and the other strongly influenced by longshore currents. To understand an entire preserved deltaic succession, the growth of multiple laterally adjacent delta lobes is modeled to define delta axial to marginal facies trends through an entire regressive–transgressive depositional succession. The goal is to refine a facies model for symmetrical wave-dominated deltas (where littoral drift diverges from the delta lobe apex). Because many factors change depositional processes on deltas, the description of the river-dominated example is included to provide a direct reference case from which to define the impact of waves on preserved facies patterns. Both systems display strong facies trends from delta axis to margin that continued into inter-deltaic areas. River-dominated delta regression preserved a dendritic branching of compensationally stacked bodies. Transgression, initiated by sea-level rise, backfilled the main channel and deposited levees and splays on the submerging delta top. Wave-dominated deltas developed dual clinoforms: a shoreface clinoform built as littoral drift carried sediment away from the river month and onshore, and a subaqueous delta-front clinoform composed of sediment accumulated below wave base. Although littoral drift in both directions away from the delta axis stabilized the position of the river at the shoreline, distributary-channel avulsions and lateral migration of river flows across the subaqueous delta top produced heterogeneities in both sets of clinoform deposits. Separation of shoreface and subaqueous delta-front clinoforms across a subaqueous delta top eroded to wave base produced a discontinuity in progradational vertical successions that appeared gradual in some locations but abrupt in others. Littoral drift flows away from adjacent deltas converged in inter-deltaic areas, producing shallow water longshore bars cut by wave-return-flow channels with associated terminal mouth bars. Transgression initiated by sea-level rise initially led to vertical aggradation of wave-reworked sheet sands on the subaqueous delta top and then retreating shoreface barrier sands as the subaerial delta top flooded. Pseudo inter-well flow tests responded to local heterogeneities in the preserved deposits. As expected, abandoned channels in the river-dominated case defined shoreline-perpendicular preferential flow paths and wave-dominated delta deposits are more locally homogeneous, but scenarios for development of more pronounced shore-parallel heterogeneity patterns for wave-influenced deltas are discussed. The results highlight the need to consider the dual clinoform nature of wave-dominated delta deposition for facies prediction and subsurface interpretation.

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