Regional Groundwater Flow Direction Research Articles

Using Expert Participation to Evaluate the Accuracy of Hand-Drawn Water-Table Maps.

Water-table maps are fundamental to hydrogeological studies and a manual, hand-drawn method is still commonly used to produce them. Despite this, the accuracy and variability of such maps have received little attention in international literature. In a unique experiment, 63 groundwater professionals drew water-table equipotential contours based on the same dataset of point measurements and were asked to infer flow directions and predict groundwater elevations at predefined locations. The root mean squared error (RMSE) for the average map calibration data was 10.5 m, which is accuracy comparable to numerical groundwater models. This study confirmed that to produce hand-drawn water-table maps, practitioners seek to not only fit the spatial data, but also to conform to their own cognitive model of hydrogeological concepts and processes. The calibration accuracy increased with experience; from a RMSE of 13.3 m for practitioners with 0-3 years of experience to a RMSE of 9.2 m for those with four or more years. Despite considerable variability in the style of the hand-drawn water-table maps, the maps were consistent in their representation of the dominant regional groundwater flow directions. There was less consensus, however, in predicting the direction of surface water-groundwater interaction for a stream reach. Hand-drawn water-table mapping remains useful and valid, especially as a starting point for hydrogeological conceptualization, yet further work is required to resolve issues around transparency, repeatability, and reproducibility.

Quantifying aquifer interaction using numerical groundwater flow model evaluated by environmental water tracer data: Application to the data-scarce area of the Bandung groundwater basin, West Java, Indonesia

Study Region:Bandung groundwater basin, Indonesia. Study focus:Groundwater abstraction of various magnitudes, pumped out from numerous depths in a multitude of layers of aquifers, stimulates different changes in hydraulic head distribution, including ones under vertical cross-sections. This generates groundwater flow in the vertical direction, where groundwater flows within its storage from the shallow to the underlying confined aquifers. In the Bandung groundwater basin, previous studies have identified such processes, but quantitative evaluations have never been conducted, with data scarcity mainly standing as one of the major challenges. In this study, we utilize the collated (1) environmental water tracer data, including major ion elements (Na+/K+, Ca2＋, Mg2+, Cl−, SO42−,HCO3−), stable isotope data (2H and δ18O), and groundwater age determination (14C), in conjunction with (2) groundwater flow modeling to quantify the aquifer interaction, driven mainly by the multi-layer groundwater abstraction in the Bandung groundwater basin, and demonstrate their correspondence. In addition, we also use the model to quantify the impact of multi-layer groundwater abstraction on the spatial distribution of the groundwater level changes. New hydrological insights for the region:In response to the limited calibration data availability, we expand the typical model calibration that makes use of the groundwater level observations, with in-situ measurement and a novel qualitative approach using the collated environmental water tracers (EWT) data for the model evaluation. The analysis in the study area using EWT data and quantitative methods of numerical groundwater flow modeling is found to collaborate with each other. Both methods show agreement in their assessment of (1) the groundwater recharge spatial distribution, (2) the regional groundwater flow direction, (3) the groundwater age estimates, and (4) the identification of aquifer interaction. On average, the downwelling to the deeper aquifer is quantified at 0.110 m/year, which stands out as a significant component compared to other groundwater fluxes in the system. We also determine the unconfined aquifer storage volume decrease, calculated from the change in the groundwater table, resulting in an average declining rate of 51 Mm3/year. This number shows that the upper aquifer storage is dwindling at a rate disproportionate to its groundwater abstraction, hugely influenced by losses to the deeper aquifer. The outflow to the deeper aquifer contributes to 60.3% of the total groundwater storage lost, despite representing only 32.3% of the total groundwater abstraction. This study shows the possibility of quantification of aquifer interaction and groundwater level change dynamics driven by multi-layer groundwater abstraction in a multi-layer hydrogeological setting, even in a data-scarce environment. Applying such methods can assist in deriving basin-scale groundwater policies and management strategies under the changing anthropogenic and climatic factors, thereby ensuring sustainable groundwater management.

Estimating Groundwater Flow Velocity in Shallow Volcanic Aquifers of the Ethiopian Highlands Using a Geospatial Technique

The shallow volcanic aquifer is the major rural water supply source in the Ethiopian highlands. A significant number of hand pump wells in these aquifers experience a rapid decline in yield and poor performance within a short period of time after construction. Hence, reliable estimation of groundwater flow velocity is important to understand groundwater flow dynamics, aquifer responses to stresses and to optimize the sustainable management of groundwater resources. Here, we propose the geospatial technique using four essential input raster maps (groundwater elevation head, transmissivity, effective porosity and saturated thickness) to investigate groundwater flow velocity magnitude and direction in the shallow volcanic aquifers of the Ethiopian highlands. The results indicated that the high groundwater flow velocity in the Mecha site, ranging up to 47 m/day, was observed in the fractured scoraceous basalts. The Ejere site showed groundwater flow velocity not exceeding 7 m/day in the fractured basaltic aquifer and alluvial deposits. In the Sodo site, the groundwater flow velocity was observed to exceed 22 m/day in the fractured basaltic and rhyolitic aquifers affected by geological structures. The Abeshege site has a higher groundwater flow velocity of up to 195 m/day in the highly weathered and fractured basaltic aquifer. In all study sites, aquifers with less fractured basalt, trachyte, rhyolite, welded pyroclastic, and lacustrine deposits exhibited lower groundwater flow velocity values. The groundwater flow velocity directions in all study sites are similar to the groundwater elevation head, which signifies the local and regional groundwater flow directions. This work can be helpful in shallow groundwater resource development and management for rural water supply.

Mineralogy and geochemistry of the Morro do Engenho lateritic nickel deposit, Goiás Alkaline Province, Brazil

The Morro do Engenho lateritic nickel deposit results from the action of weathering processes on the alkaline mafic-ultramafic rocks that make up the Cretaceous zoned intrusive body belonging to the Goiás Alkaline Province. Historically, the deposit is classified as a silicate one, and mineralization is present especially in phyllosilicates such as serpentine and chlorite. By identifying Ni-bearing phases and providing the lithogeochemical characterization of weathering profiles, this study aims to provide further insights into the metallogenetic processes and controls acting on the mineralization of the Morro do Engenho lateritic Ni deposit. The following methods were used: petrographic studies, SEM-EDS, XRD and lithogeochemical characterization of the weathering profiles developed on each of the parent rocks that make up the body. The Morro do Engenho intrusive massif is formed by a dunite core, surrounded by a peridotite/pyroxenite zone, an alkaline gabbro zone and more externally by a syenite-nepheline zone. The lateritic profile constitutes eight weathering horizons, stacked one upon another from the bedrock namely: (i) saprock, (ii) lower saprolite, (iii) ferruginous saprolite, (iv) ocher saprolite, (v) plasma zone, (vi) lateritic duriccrust, (vii) silcrete and (viii) topsoil. Most Ni mineralization occurs in the lower saprolite, ferruginous saprolite and ocher saprolite zones. The findings pointed to the presence of Ni in silicate mineral phases, represented by serpentine, chlorite, smectite, as well as in Fe and Mn oxyhydroxides. The depressed area, located between the two major topographic elevations, has the highest Ni enrichments, which according to mass balance calculations can account for up to 40%. Hydrodynamic factors, by dissolution/precipitation of silicates in saprolite horizons of dunite core, are suggested as possible agents in the remobilization of Ni, among other mobile elements, to topographically flat zones. The geometry of the Morro do Engenho deposit show that lateral redistribution by hydrodynamic factors could also account for the mineralization of areas peripheral to the dunite core, composed of pyroxenite and gabbro-derived lateritic profiles. The direction of regional groundwater flow, strongly influenced by topography, would also be an important factor in the remobilization of Ni, as well as the mechanical transport of lateritic materials. Silicate mineralization predominates in the Morro do Engenho deposit, concentrated in Mg hydrosilicates and clay minerals; oxide mineralization also occurs, mostly in Fe and Mn oxyhydroxides. The findings discussed in this paper can broaden the understanding of metallogenetic processes involved in the genesis of lateritic nickel deposits. .

Identifying groundwater recharge and discharge zones using geostatistical simulation of hydraulic head and its derivatives

Identifying groundwater flow directions and the locations of recharge and discharge areas is critical for effective groundwater management. Groundwater flow directions, the concavity and the locations of extrema (i.e., minima and maxima) can be assessed using the first and second derivatives of the hydraulic head surface. We developed a geostatistical method to jointly simulate hydraulic head and its first and second derivatives using sequential Gaussian simulation. The derivative values were used to identify regional groundwater flow directions, and the second derivative test was used to probabilistically map the concavity and the locations of extrema in the hydraulic head surface. By comparing the mapped concavity and extrema to known features, it was possible to attribute areas of recharge and discharge to physical features of the system, such as rivers, lakes and geological outcrops. This was applied to Triassic aquifers in the Galilee Basin (Queensland, Australia) to delineate the likely recharge and discharge areas. This provided an objective assessment of likely recharge and discharge zones and their uncertainty, which is an important addition to a region where the hydrogeology has been the subject of much conjecture.

Deep Groundwater Flow Patterns Induced by Mine Water Injection Activity

Mine water injection into deep formations is one of the effective approaches for reducing the drainage from coal mines in the arid and semi-arid region of the Ordos basin, China. Many coal mines are attempting to execute the related projects. Under the influence of groundwater protection, the understanding of regional groundwater flow is becoming highly important to the mine water monitoring, whereas quite few academic research teams focus on the deep groundwater flow pattern by mine water injection. This paper reveals the spatial distribution of Liujiagou Formation that is in positive correlation with the terrain, and its local thickness is influenced by the dominant W-E and NE-SW directions of geological structures. Only a part of sandstone rocks consists of aquifers, the rest 61.9% of relatively dry rock provide the enhanced storage space and partial mudstone aquicludes decrease the possibility of the vertical leakage for mine water. The dynamic storage capacity is evaluated at 2.36 Mm3 per 1 km2 and over 25.10 billion m3 in this study area. Two hydrogeologic cross-sections of basin-scale identify the W-E and N-S regional groundwater flow directions, with the lower Yellow River catchment becoming the discharged region. The hierarchically and steadily nested flow systems containing coal mining claims are influenced by coal mining activity. The groundwater depression cone in a shallow coal measure aquifer is caused by mine water drainage whereas the groundwater mound in Liujiagou Formation is generated by mine water injection activity. The numerical simulation revealed that the groundwater head rebound is slightly decreased and will not recover to its initial baseline within 500 years due to its low porosity and permeability. This study elucidates the deep groundwater flow patterns induced by mine water injection and provides a practical methodology for the management and pollution monitoring of mine water injection activity.

Identifying nitrate sources and transformation in groundwater in a large subtropical basin under a framework of groundwater flow systems

Land use patterns and regional hydrogeological conditions have a great impact on nitrate sources and transformation in groundwater at the large-basin scale. In this study, hydrochemistry, multiple isotopes (δD-H2O, δ18O-H2O, δ15N-NH4+, δ15N-NO3- and δ18O-NO3-), and a Bayesian model were integrated to identify nitrate sources and transformation in groundwater in the Qingyi River basin (QRB), a large subtropical basin in East China. Overall, increases in total dissolved solids, NO3-, and decreases in d-excess and dissolved oxygen concentrations were observed along the regional groundwater flow direction, suggesting groundwater in recharge and transition areas had fewer anthropogenic N inputs, shorter residence times, and more oxidizing environments. As demonstrated by the negative correlation of δ15N-NH4+ and δ15N-NO3-, nitrification was dominant in recharge and transition areas, and δ18O-NO3- values above theoretical nitrification line indicated a mixing of atmospheric NO3- and nitrified NO3-. By contrast, denitrification was a major transformation in discharge areas. In recharge areas (with an area of 95.9% forest), soil organic nitrogen and atmospheric precipitation contributed 82.7% and 17.3%, respectively. In transition areas (54.3% forest, 42.5% farmland), the major nitrate sources were soil organic nitrogen (38.7%) and chemical fertilizer (27.7%). In discharge areas (52.4% farmland, 15.0% residential area), manure/sewage and soil organic nitrogen accounted for 34.6% and 28.4% of total nitrate. High soil organic nitrogen contribution in the QRB suggested land use in recharge areas is essential for controlling the groundwater nitrate contamination in basins. Finally, we proposed a conceptual model of the nitrate sources and transformation in groundwater in the QRB, revealing the nitrate behaviors in groundwater in a large basin within a framework of groundwater flow systems. This study proves that groundwater flow system is effective to fuse multi-information to identify nitrate sources and fate in groundwater in a large basin, which is helpful to regional groundwater management and protection in similar subtropical basins.

Geostatistical Mapping of Salinity Conditioned on Borehole Logs, Montebello Oil Field, California.

We present a geostatistics‐based stochastic salinity estimation framework for the Montebello Oil Field that capitalizes on available total dissolved solids (TDS) data from groundwater samples as well as electrical resistivity (ER) data from borehole logging. Data from TDS samples (n = 4924) was coded into an indicator framework based on falling below four selected thresholds (500, 1000, 3000, and 10,000 mg/L). Collocated TDS‐ER data from the surrounding groundwater basin were then employed to produce a kernel density estimator to establish conditional probabilities for ER data (n = 8 boreholes) falling below the selected TDS thresholds within the Montebello Oil Field area. Directional variograms were estimated from these indicator coded data, and 500 TDS realizations from conditional indicator simulation were generated for the subsurface region above the Montebello Oil Field reservoir. Simulations were summarized as 3D maps of median TDS, most likely salinity class, and probability for exceeding each of the specified TDS thresholds. Results suggested TDS was below 500 mg/L in most of the study area, with a trend toward higher values (500 to 1000 mg/L) to the southwest; consistent with the average regional groundwater flow direction. Discrete localized zones of TDS greater than 1000 mg/L were observed, with one of these zones in the greater than 10,000 mg/L range; however, these areas were not prevalent. The probabilistic approach used here is adaptable and is readily modified to include additional data and types and can be employed in time‐lapse salinity modeling through Bayesian updating.

Integrated hydrogeological, hydrochemical and environmental isotope investigation of the area around the Kusile Power Station, Mpumalanga, South Africa

This integrated hydrogeological, hydrochemical and environmental isotopes (δ2H, δ18O, 3H) study has been undertaken to investigate the hydrogeological conditions around the Kusile coal-fired power station located in Mpumalanga province of South Africa. The study area is characterized by mainly weathered and fractured and fractured secondary aquifer systems. Boreholes drilled in both aquifer systems have yields ranging from 0.1 to 2 L/s. The regional groundwater flow directions follow the topographic gradient. Hydrochemical analysis of water samples from 25 boreholes, 6 springs, and 19 surface water points show electrical conductivity (EC) values less than 700 μS/cm, pH values range from 5.2 to 9.6. The hydrochemical data shows six hydro-chemical facies with Mg–HCO3 as the most dominant facies indicating a shallow circulating less evolved recharge area groundwater. The results of the statistical multivariate factor analysis of hydrochemical data indicates three factors that explain the main ions’ contribution to water salinity (EC), some reducing conditions and carbonate buffering on the pH of the system, respectively. Environmental isotope data indicates that groundwater is recharged from local rainfall and the residence time of groundwater in the aquifer system is relatively short, ranging from 7 to 36 years. Similarity in isotopic signature between surface water and groundwater samples indicate groundwater - surface water interactions. The results of high sulphate concentration in some groundwater and surface water samples indicates that the coal mining activities taking place within the catchment and the coal-fired Power plant operations have impacted the water resources. However, due to natural carbonate buffering reactions, the pH of the high sulphate groundwater and surface water is neutral to alkaline and the EC is moderately low.

The influence of riverbank filtration on regional water resources: a case study in the Second Songhua River catchment, China

Abstract Riverbank filtration (RBF) of river water recharging a groundwater system has been identified as a source of water supply that guarantees the quantity of abstracted water and reduces the cost of water treatment. This paper evaluates the safe yield of groundwater in suitable areas using a numerical model of groundwater flow and discusses the influence of RBF on the temporal variation of regional hydraulic heads, groundwater flow, river flow, and groundwater–surface water interaction (GSI) under different precipitation frequencies from 20% to 95% along the Second Songhua River in Northeast China. This study shows that the potential of RBF is enormous and that the total safe yield of groundwater abstraction was 29.56 × 104 m3/day under the precipitation frequency of 95%. The direction of regional groundwater flow was not obviously changed except within the local groundwater flow field under the maximum safe yield pumping conditions. When the precipitation frequencies are higher than 75%, the direction of the GSI might be changed, and the rate of river recharge of groundwater is enhanced. The water quantity that would be captured from the river does not threaten the safety of the river ecology. It is concluded that there were no obvious adverse impacts of the large scale of RBF on regional water resources in the Second Songhua River area.

Hydrogeology of Eastern Niger Delta: A Review

This paper characterizes the aquifer system of the Niger Delta for sustainable development of the groundwater resource. The heavy-dependence on groundwater in the region and the fears of its unsustainability triggered by the weak regulations, pollution, increasing user population and industrialization coupled with the present limited knowledge of the true geological condition prevailing within the groundwater domain of the Niger Delta are the considerations that compelled this review study. The hydraulic properties of the region’s aquifers are discussed. The Niger Delta is characterized by a complex multilayered aquifer system hosted in the Benin Formation with the main body of fresh water, with increasing occurrence of intercalating clay units towards the coast. Lithological analysis indicates the prevalence of unconsolidated sand and sandy gravels in the aquiferous horizons, presenting them as pervious and prolific aquifers. Reported hydrochemical data gathered from wells drilled suggest that the quality of groundwater in the Niger Delta is considered generally very good and compares favorably with WHO standards for drinking water. However, relatively high iron/manganese and chloride values are localized in time and space. In the coastal areas however, seawater intrusion has been identified as one of the major influences on hydrochemistry of groundwater in the shallow unconfined aquifers. Regional groundwater flow direction is from north to south. Changes in groundwater flow directions which occur at some places generally serve localized discharge areas. The resultant flow path eventually joins and feeds the major regional north-south flow direction. The increasing pressure on groundwater, the need for urgent attention and the absence of strong institutions and regulations have made the management of groundwater resources in the region a difficult task. Therefore, future ground water resources development in the Niger Delta requires adequate observational data, investments in infrastructure and an integrated management approach to ensure optimal basin-wide benefits.

Integrating transient behavior as a new dimension to WHPA delineation

Abstract The protection of groundwater abstraction is primarily based on the delineation of “time-of-travel capture zones” known as Well Head Protection Areas (WHPAs). Their delineation is subject to several uncertainties: the scarcity of hydrogeological data due to limited budgets for exploration and additional uncertainty from time-varying flow conditions. While the former has lead to the use of probabilistic strategies, no existing approaches for WHPA delineation consider jointly geological uncertainties, transient flow conditions and the associated additional uncertainties. We propose to extend existing steady-state probabilistic approaches for WHPA delineation to account for transient flow conditions and their related uncertainties. In our synthetic scenario, transiency is represented through four selected transient drivers: (I) regional groundwater flow direction, (II) regional strength of the hydraulic gradient, (III) natural groundwater recharge and (IV) pumping rate. As a result of our proposed probabilistic framework, we obtain probabilistic catchment maps that consider the joint effect of (uncertain) transient flow conditions and geological uncertainty. To represent hydraulic conductivity we use a random space function using a Matern covariance function. In order to reduce computational costs, so that we can conduct Monte Carlo analysis over both sources of uncertainty, we represent transiency as a dynamic superposition of steady-state flow solutions. Overall, we show that (1) each transient driver defines a distinctive pattern of temporal catchment membership, with the ambient flow direction driving most of the changes. (2) The transient analysis enhances decision support for probabilistic WHPA delineation by providing additional information in terms of time reliability levels. Now, a WHPA can be defined from this analysis by selecting a reliability level for time and one for geological uncertainty. (3) Time reliability addresses a different kind of risk when compared to geological reliability: While a lack of time reliability implies a known risk to the well for a fraction of time, a lack of geological reliability means that one does not know whether the well is at risk. (4) In the presence of uncertain transient and geological conditions, high time reliability levels are cheap compared to high reliability levels against geological uncertainties. (5) The combined use of time-geological reliability information with land use information leads towards more targeted risk reduction measures that align with the two different types of risk addressed by time reliability and geological reliability.

Design and and Construction of Groundwater Monitoring Network at Shallow-depth CO2 Injection and Leak Test Site, Korea

The effectiveness of CO2 leakage characterization is highly dependent on reasonable monitoring network designs for detecting the CO2 leakage under various hydrogeological conditions. Also, the migration of CO2 through heterogeneous subsurface is very difficult to predict because small differences in material properties may result in vastly different migration patterns. Therefore, like other environmental contaminants, it is necessary to design optimized groundwater monitoring network to effectively characterize the migration of the CO2. Main objectives of this study is to construct optimized groundwater monitoring network considering hydrogeological characteristics in field-scale transport of CO2 originated from artificially-injected CO2 at the environmental impact monitoring test site in Eumseong, Korea (K-COSEM). 24 monitoring wells were installed at the site aligned with the regional groundwater flow direction. Various hydraulic tests were performed to estimate the hydraulic characteristics such as hydraulic conductivity, effective porosity, and groundwater velocity. Groundwater monitoring network for CO2 injection and leak test constructed with regard of the heterogeneity understood through the various field tests. Three multi-depth monitoring well nests each of them was composed of four monitoring well units drilled with different depths (each 18, 22, 26, 30 m deep) have been installed along the groundwater flow direction and dedicated to depth-discrete water quality monitoring in saturated zone. Additional, four multi-depth monitoring well nests each of them was composed of four unsaturated-zone monitoring well units drilled with different depths (each 5, 8, 11, 14 m deep) were also installed with a distance of 1.25 m away between saturated zone monitoring wells and were dedicated to depth-discrete gas monitoring in unsaturated zone. By these efforts, effective groundwater monitoring network for temporal and spatial CO2 leakage detection and groundwater safety management have been designed and constructed at the test site.

Stable isotopes, carbon-14 and hydrochemical composition from a basaltic aquifer in São Paulo State, Brazil

The Cretaceous Serra Geral Aquifer (SGA) is contained within one of the largest continental flood basalts in the world, reaching a thickness up to 1700 m in the center of the Parana Basin. The SGA is one of the most important groundwater reservoirs in northeastern Sao Paulo State (Brazil), responsible for water supply to cities and agriculture. In order to evaluate the geochemical and isotopic evolution of SGA, as well as to determine the mean residence time, a groundwater sampling campaign was carried out over the SGA in Sao Paulo State (Brazil) from January to April 2013. Two main hydrochemical facies were recognized: Ca–Mg–HCO3 related to water–rock interaction reactions in basaltic outcrop, such as mineral dissolution due to atmospheric CO2 uptake, and alkaline Na–HCO3 groundwater, evolved from mixing with groundwater from the underlying Guarani Aquifer System. Stable isotope (δ18O and δ2H) ratios range from −8.87 to −5.32‰ VSMOW and −61.31 to −31.64‰ VSMOW, respectively, closely following the GMWL. Spatial and temporal variations in isotope ratios are associated with the South Atlantic convergence zone activities and the type of rain responsible for recharge. Values for δ13C vary from −21.53 to −7.11‰ VPDB, while 14C activities vary from 1.2 pcm to more than 100 pcm, presenting a trend to enrichment and decrease in 14C activities westward, concordant with the regional groundwater flow direction. Most recent groundwaters have δ13C ratio contents mostly consistent with C3 plants.

To Study Hydrogeology and Wetland-Groundwater Interactions around Sukhna Wetland, Chandigarh, India

In the present paper the hydrological regime around Sukhna wetland is studied to know how a wetland is functioning, its influence on hydrology of the area and wetland-groundwater interactions. The subsurface geology of boreholes drilled around Sukhna wetland reveals thick zones of boulders, pebbles, gravels, sand and clay at different depths. In this area there are two type aquifer systems i.e., shallow and deep. The depth for shallow aquifer ranged 2-20 m bgl and in deeper aquifers ranged 10 above 40 m bgl. The water level fluctuations for the period 1985-2013, indicates the declining water level trend in both the seasons i.e., pre monsoon (May) and post monsoon (November) due to over exploitation by tubewells installed by the Public Health Department, UT, Chandigarh for providing domestic water supply. The water table elevation contour maps for May and November months in Chandigarh for years 1986, 1991, 1999, 2005 and 2012 reveals that the regional ground water flow direction is from Northeast to Southwest and there in no significant temporal variations in regional ground water flow direction. On the basis of hydrological regime study around Sukhna wetland it is inferred that no appreciable rise in water levels has been observed around Sukhna wetland but it is contributing recharge in the upper shallow aquifer system in the central part of Chandigarh and below as the subsurface groundwater flow is towards south and south west direction

Examination of water budget using satellite products over Australia

Large-scale water balance in the Australian continent is examined over an 8-year period (2003–2010) with three commonly used satellite based water cycle components: precipitation (P) from the Tropical Rainfall Measuring Mission (TRMM), evapotranspiration (ET) from the Moderate Resolution Imaging Spectroradiometer (MODIS), and terrestrial water storage change (ΔS) from the Gravity Recovery and Climate Experiment (GRACE). First we evaluate the water balance using the three products over areas with limited annual streamflow to eliminate the influence of runoff in the analysis. We observe more frequent and better closure and consistency in the water balance from the three components over the central part of Western Australia, where low precipitation, high elevation and low relief exist. The data are more coherent at seasonal and annual scales compared to the monthly scale. Application of the three products in Lake Eyre Basin (an internal drainage system) suggests a maximum 6.2 mm/year groundwater inflow to the basin, which is consistent with the regional groundwater flow direction in the area. This result also indicates that the absolute integrated error of the combination of three products should be smaller than 6.2 mm/year, which is about 2.1% of annual precipitation in the basin. If this relative error is assumed for the whole continent, water balance calculation using the three products over the whole Australian continent results in 144.7 ± 11.3 mm/year estimated total runoff to the surrounding oceans during the study period. We found that this estimate is comparable to the estimates of 50–150 mm/year from the Australian Bureau of Meteorology and National Water Commission.

Assessment of Baseline Groundwater Physical and Geochemical Properties for the Quest Carbon Capture and Storage Project, Alberta, Canada

Abstract The Shell Quest Carbon Capture and Storage (CCS) project will capture CO2 from the Scotford Upgrader Facility in Fort Saskatchewan, Alberta, Canada, and inject approximately 1 million tonnes of CO2 per annum over 25 years into the Basal Cambrian Sandstone aquifer. An MMV program has been designed and is being implemented. A key MMV component is the ongoing hydrological and geochemical monitoring of a number of groundwater wells. As part of the MMV process, this project has re-evaluated the shallow geology in the study area where necessary, and based upon this, defined four aquifers including the Surficial, Oldman, Foremost and Basal Belly River Sandstone (BBRS). Historic and ongoing groundwater monitoring data has been used to develop a hydrologic and geochemical baseline for the four target aquifers. Inferred regional groundwater flow directions and velocities have been calculated based upon the available hydraulic head, well pump test data and aquifer properties. Groundwaters from the Surficial, Oldman and Foremost aquifers cannot be separated based upon hydraulic head or upon aqueous chemistry. However, groundwater data from the BBRS aquifer suggests that the BBRS aquifer is hydraulically isolated from the overlying aquifers within the limits of the Quest Project Sequestration Lease Area (SQL). Based on the geochemical baseline, groundwater related solution chemical triggers are being defined which may be used to identity whether or not fluid and/or gas migration is occurring from the storage complex and, if that is the case, what impact those fluids and/or gas may have upon the potable groundwaters above the Base of Groundwater Protection (BGWP) across the SQL.

Effects of regional groundwater flow on the performance of an aquifer thermal energy storage system under continuous operation

Numerical investigations and a thermohydraulic evaluation are presented for two-well models of an aquifer thermal energy storage (ATES) system operating under a continuous flow regime. A three-dimensional numerical model for groundwater flow and heat transport is used to analyze the thermal energy storage in the aquifer. This study emphasizes the influence of regional groundwater flow on the heat transfer and storage of the system under various operation scenarios. For different parameters of the system, performances were compared in terms of the temperature of recovered water and the temperature field in the aquifer. The calculated temperature at the producing well varies within a certain range throughout the year, reflecting the seasonal (quarterly) temperature variation of the injected water. The pressure gradient across the system, which determines the direction and velocity of regional groundwater flow, has a substantial influence on the convective heat transport and performance of aquifer thermal storage. Injection/production rate and geometrical size of the aquifer used in the model also impact the predicted temperature distribution at each stage and the recovery water temperature. The hydrogeological-thermal simulation is shown to play an integral part in the prediction of performance of processes as complicated as those in ATES systems.

A Revised Conceptual Model to Reproduce the Distribution of Chlorinated Solvents in the Rho Aquifer (Italy)

AbstractTo make cost‐effective decisions regarding aquifer protection against chlorinated solvent contamination, a conceptual site model explaining the hydrodynamic behavior of these solvents needs to account for soil heterogeneities in sufficient detail. Among the key requirements, it is necessary to perform site‐specific characterization of (1) the architecture and type of chlorinated solvent sources, (2) the architecture, nature, and distribution of aquitards (bodies of low permeability), and (3) local groundwater dynamics. Local‐scale data are often lacking and regional descriptions are therefore adopted with the consequence of losing small‐scale features that control local chlorinated solvent migration which, in turn, limits the effectiveness of safeguard facilities. This article addresses these arguments, focusing on the Rho aquifer (Italy). We show that the local conceptual model must integrate small‐scale architectural and hydrodynamic anomalies of the aquifers and aquitards with regional trends and the sedimentary origin of the aquifers. New evidence was found by processing stratigraphic logs, piezometric heads and solute concentrations from local wells. The revised conceptual model should account for the occurrence of secondary chlorinated solvent sources located in depressions on the aquitard surface separating the two upper and most contaminated Rho aquifers. While the spatial distribution of depressions is in accordance with regional sedimentological dynamics, the direction of local groundwater flow at various levels within the main hydrogeological unit is remarkably opposite to the regional groundwater flow direction. These findings, along with evidence of vertical heterogeneous soil texture and stratification of chlorinated solvents in various phases, are supported by a simple particle‐tracking model and suggest how to redefine the conceptual model and, consequently, how to design safeguard facilities to effectively prevent further plume migration.

Hydrogeological analysis of the upper Dupi Tila Aquifer, towards the implementation of a managed aquifer-recharge project in Dhaka City, Bangladesh

A preliminary feasibility assessment of managed aquifer-recharge (MAR) techniques was undertaken for Dhaka City, Bangladesh. Considering the top impermeable-layer (TIL) thickness and the land-use classification, four primary MAR techniques have been suggested: (1) soil-aquifer treatment (SAT) for TIL thickness 0–8 m, (2) cascade-type recharge trenches/pits for TIL thickness 9–30 m, (3) aquifer storage, transfer and recovery (ASR/ASTR) for TIL thickness 31–52 m, and (4) use of natural wetlands to recharge water collected from open spaces. The study suggests that recharge trenches and pits will be the most appropriate MAR techniques, which can be implemented in most parts of the recharge area (ca. 277 km2). In case of a recharge trench, the lower parts (15–20 m) that are in direct contact with the aquifer can be backfilled with biosand filters with a reactive layer containing metallic iron (Fe0) to offer pre-treatment of the infiltrated water. In addition to the suggested four techniques, the regional groundwater flow direction, from the northwest and northeast towards Dhaka City, may allow use of the aquifer as a natural treatment and transport medium for groundwater, if spreading basins are installed in the greater Dhaka area.