Aquifer Recharge Areas Research Articles

Identifying Karst Aquifer Recharge Area Using Environmental Stable Isotopes and Hydrochemical Data: A Case Study in Nusa Penida Island

Identifying the recharge area of karst aquifers is scientifically challenging due to the complexity of karst groundwater flow characteristics. It is essential to identify the recharge zones to conserve the groundwater resources contained within these aquifers. This paper proposes a combined methods for identifying recharge area of karst aquifers on Nusa Penida Island using stable isotopes (18O and 2H) and a hydrogeochemical approach. Based on the analysis of δ18O and δ2H values and their spatial distribution, it is possible to retrace karst aquifer recharge areas using average isotope elevations. In the meantime, groundwater facies will be determined in the karst region of Nusa Penida using the hydrogeochemical approach with the Piper diagram. According to the calculation of water stable isotope results, the average elevation of the groundwater recharge area at the study site is between 62 - 450 meters. If applied to the location of the study, the recharge area is almost entirely distributed across Nusa Penida. In addition, based on the hydrogeochemical analysis, the groundwater type at the study site can be divided into three categories: Na-Cl, mixed, and Mg-HCO3. The water types indicate that the groundwater in Nusa Penida comes from a combination of old water stored from its internal geological formations and mix with modern rainwater.

Application of hydrogeophysics and diagnostic plots in setting up a sustainable managed aquifer recharge scheme, West Coast, South Africa

The lack of using hydrogeophysics and hydraulic data in setting up a sustainable managed aquifer recharge scheme leads to challenges in operations and maintenance of such infrastructures. Managed aquifer recharge is an engineering and technological based water management approach that is used to maximize storage and improve groundwater security. However, this approach is under-utilized in many countries and South Africa is no exception. This study aimed at improving knowledge on aquifer dynamics for managed aquifer recharge scheme using hydrogeophysics and diagnostic plots. This study argued that integrating hydrogeophysics data and diagnostic plots for setting up managed aquifer recharge schemes lead to improved operations and maintenance through improved scientific knowledge on the dynamics of the aquifer. SkyTEM and electrical resistivity tomography data were used to delineate subsurface structures. Pumping test data were used to develop diagnostic plots, for identifying flow regimes and boundary conditions in the proposed managed aquifer recharge area. Results from geophysics investigation inferred pathways for potential managed aquifer recharge and areas to avoid. The integration of hydrogeophysics and diagnostic plots provided a more practical interpretation for the study area. It is recommended that hydrogeophysics investigation should be carried out before and after setting managed aquifer recharge scheme as it leads to enhanced decisions on groundwater usage, monitoring and management.

Impacts of urban sprawl in the Administrative Region of Ribeirão Preto (Brazil) and measures to restore improved landscapes

The present study addressed the problem of urban expansion in a large metropolis of Brazil (ARRP – Administrative Region of Ribeirão Preto), relating the evolution of urbanization in the past 35 years with losses of agricultural area and respective equivalent production and economic effects. Besides these food security and agribusiness issues, the study tracked important environmental consequences of the observed growing urbanization. This included water insecurity related with the occupation of watercourse networks, destruction of riparian vegetation that is legally protected as Permanent Preservation Areas (PPAs), and the occupation of Guarani Aquifer recharge areas with impermeable surfaces. The database consisted of Landsat images interpreted and processed in a Geographic Information System (GIS). The results indicate losses of rural area exceeding 350 km2 in the studied timeframe, with equivalent production and economic losses around 1.1 Mton/year and 230 MR$/year, on average. It is worth to mention the 40–75% overlap between the impermeable surfaces of some ARRP municipalities (e.g., Cajuru, Altinópolis) and recharge areas of Guarani Aquifer. The impermeable surfaces within the ARRP also affected approximately 7000 headwaters that were potential hotspots of shallow aquifer recharge. The urban sprawl destroyed more than 9100 km of natural watercourses and nearly 630 km2 of PPAs. The pathways recognized to improve the ARRP landscape included implementation of urban agriculture and landscape planning measures capable to protect the recharge to and the quality of Guarani Aquifer water, mostly anchored in the Municipal Director Plans, the prominent land use policy tools in the ARRP. This integrated, long-term, spatially explicit and quantitative assessment of urban sprawl impacts assembled with indications of landscape restoration policies and measures is novel in Brazil. On the other hand, studying the ARRP is worthwhile because of its historical relationship with the Brazilian ethanol program that brought an accelerated development to the region following the World oil crisis of 1970 s until now.

Contamination assessment and potential sources of heavy metals and other elements in sediments of a basin impacted by 500years of mining in central Mexico.

Since the middle of the 1500s, mining has been active in central Mexico. Total estimates for low-grade piles and mine tailing materials in the Guanajuato mining district (GMD) are in the range of 150 million tons, covering an area of 15 to 20 km2. GMD is located in the Guanajuato River sub-basin (GRB), which is part of one of the largest basins in Mexico (Lerma-Santiago). Previous studies on the GRB found unusually high concentrations of heavy metals in mining tailings and sediments. Geochemical and statistical methods were used here to determine the sediment's origin, background values, degree of contamination, and toxicity through different contamination indices. This analysis shows that Cu, Co, As, Sb, and Hg are higher than they are in the upper continental crust (UCC) overbank sediments without human and mining influence, because of the ore deposits and rock weathering in GRB. Geochemistry results in stream sediments show anomalies, where Hg, Cu, Zn, As, and Pb are higher than UCC because those heavy metals and trace elements (HMT) have been influenced by human activities and mineral recovery (smelting, amalgamation, cyanidation). The distribution of high concentrations of HMTs and contamination indices occur in the main channel of the Guanajuato River and downstream of the city of Guanajuato. Statistical analyses (cluster and principal component analysis) reveal relationships between Cr, Ni, Cu, and Pb, which are primarily of natural origin, related to rocks of the upper basin. The middle and lower basins are distinctive in their associations between As, Sb, Zn, Pb, and Hg. Additionally, it is recognized that the origins of Pb, Zn, and Hg are geogenic and anthropogenic. This study demonstrates how crucial it is to understand the geochemistry of various HMT sources, with both natural and anthropogenic contributions (stream sediments and rocks), in order to calculate a more realistic background in a basin with both natural anomalies and anthropogenic contamination. The basin is a regional aquifer recharge area, so the new geochemical data are important for improving basin environmental management.

Atrazine pollution in groundwater and raw bovine milk: Water quality, bioaccumulation and human risk assessment

Atrazine herbicide can bioaccumulate over time and thus affect humans for generations to come. However, scarce studies have evaluated its bioaccumulation potential in bovine milk, a nutritional staple for children and the elderly both domestically and internationally. This study aimed to determine its concentration in groundwater and bovine milk, as well as the risks it is likely to pose for human health. Eighteen dairy farms in the Pampean plain of Argentina were analyzed. A strong correlation was found between the chemical composition and the geomorphological characteristics of the plain. In addition, increased salinity was observed in the groundwater at greater distances from the aquifer's recharge area. Atrazine was quantified in 50 % of the groundwater samples (at values ranging from 0.07 to 1.40 μg/L), and in 89 % of the bovine milk samples (from 2.51 to 20.97 μg/L). Moreover, atrazine levels in 44.4 % of the groundwater samples and 11.1 % of the bovine milk samples (n = 18) exceeded the limits internationally established as safe for human consumption. The hazard quotient (HQ) values of the compound were negligible for children and adults, both in groundwater (child = 9.7E-4, adult = 4.5E-4) and in milk (child = 1.0E-2, adult = 1.6E-3). The estimated cancer risk (CR) values need further evaluation (child = 7.8E-6, adult = 3.6E-6 in groundwater; child = 6.6E-5, adult = 1.3E-5 in milk). In both types of samples, the HQ and CR of residual atrazine were higher for children than for adults. Nevertheless, bioaccumulation factors suggest that dairy cows have a moderate capacity to incorporate atrazine from abiotic matrices. This is the first report on residual atrazine in bovine milk in Argentina. The results presented here indicate that the status of atrazine contamination in the area should continue to be monitored in order to assess its long-term impact on public health.

Assessing and delineation of groundwater recharge areas in coastal arid area southern Tunisia

In Gabès region (southeastern Tunisia), given the semi-arid to arid climate conditions, groundwater is an essential resource to supply the growth needs of the socio-economic development. To ensure sustainable development and preserve water resources, a careful estimation of the present day recharge amount and the delineation of the potential zones of rainfall precipitation are of required for an accurate evaluation of regional water balance. In this context, this study aims to a preliminary assessment of groundwater recharge in Gabes basin in regard to the delineation of the potential recharge areas of phreatic aquifers. Thus, a geological and hydrogeological collected database coupled with remote sensing techniques (RST) were used for the determination of the lateral variation of recharging zone, Treatment by ArcGIS and Matlab softwares and Kohonen self-organizing maps (K-SOM) approaches. The obtained results indicate that five recharge potential areas have been identified and classified as 27% very low, 23% low, 40% moderate recharge, 7% good and 3% very good potential recharge located principally on southern part of the study region. This distribution is controlled principally by the geomorphological, geologic, and hydrogeologic features of the region. Reasonable management strategies based on a perennial exploitation of these low renewable resources are required to optimize the water dependent socio-economic development. The estimated groundwater potential recharge of Gabès aquifer system using K-SOM and RST is of 11.4 Mm3 y−1. This recharging rate is very low it present 7% of the total rain, thus it must be ameliorated. K-SOM and RST approach is a useful method for groundwater potential recharge mapping and is a helpful of wells establishment and groundwater sustainable management. an isotopic analyses is recommended to ameliorate the decision maker to establish the adequate strategy.

Anthropic Influences on the Quality of Underground Waters for Human Consumption in Russas, Ceará, Northeastern Brazil

In regions with semi-arid characteristics, groundwater is a precious source of water supply, mainly from alluvium, due to the decent quality of its waters. However, the sandy texture favors vulnerability, and the infiltration and percolation of fluids increase the risk of contamination of the aquifer in the presence of polluting sources. The population’s knowledge about these problems is still ephemeral, which can lead to the consumption of contaminated water, putting health at risk. Thus, research was conducted in the municipality of Russas – Ceará, to study the quality of groundwater, the possible polluting sources in the urban area, and assess the possible risks to human health. First, technical visits for reconnaissance and survey of information were conducted, such as possible polluting sources and situations of existing wells. The selection of wells to collect water followed criteria of proximity to polluting sources, well conditions, and, mainly, those linked to the use of water for human consumption. The result showed that 43% of the samples are above the limits proved by Brazilian legislation for turbidity, total hardness, TDS, sodium, chloride, and nitrate, while the others are withinthe standard. Concerning chlorides and nitrates, the concentrations show there is possibly a relationship with anthropic contaminants(agricultural area; domestic effluents) for the aquifer recharge areas and condition common problems to human health. Therefore, it is of paramount importance to continue research in Medical Geology that will enable the monitoring and future management of water quality of groundwater for the population.

Application of square array configuration and electrical resistivity tomography for characterization of the recharge area of a karst aquifer: A case study from Menekşe karst plateau (Kocaeli, Turkey)

Groundwater recharge characteristics of a karst plateau which plays an important role in the recharge of a regionally important highly productive karst aquifer was revealed by combined application of Electrical Resistivity Tomography (ERT) and Square Array Configuration methods. A forward model of targeted karst features and geological structures constructed prior to ERT survey enabled a more comprehensive and more reliable interpretation of the real data. The transition between the anomalies resulted from different structures were sharp and the artifacts were distinct in the inverted sections of the synthetic data whereas a smoother transition was observed between different types of anomalies in the real data and the artifacts were harder to be distinguished from the anomalies related to the real subsurface structures. The air-filled karst shafts and caves inside the Triassic aged marbles resulted in high resistivity anomalies approximately between 3000 and 6000 Ωm. On the other hand, clay rich soil zones and water bearing fissure networks led to low resistivity anomalies ranged between 100 and 400 Ωm. ERT survey detected various well karstified fast recharge zones and indicated that the network of karstified zones dipped through northeast (NE). The method also pointed out that nonkarstified fissure networks and thick layers (10–15 m) of clay rich soil zones leading to a lagged recharge existed some regions in the plateau. Square Array Configuration survey signified that dominant fracture zones existed in SW-NE and NW-SE directions and indicated that the faults and fractures in the region (SE-NW and SW-NE oriented) extended deep inside the karst aquifer. Overall evaluation of ERT and Square Array Configuration results enabled the determination of fast and slow recharge zone distribution throughout the karst plateau and thus, distinguished the highly sensitive regions in karst plateau for groundwater contamination. Finally, this study showed that combined application of Square Array Configuration and ERT surveys could successivley characterize groundwater recharge in a complex karst terrain and could constitute a supportive method for revealing the spatial vulnerability differences of a karst region to groundwater contamination.

Effects of Decaying Hydraulic Conductivity on the Groundwater Flow Processes in a Managed Aquifer Recharge Area in an Alluvial Fan

Groundwater artificial recharge and medium characteristics represent the major factors in controlling the groundwater flow processes in managed aquifer recharge areas. According to the depositional features of alluvial fans, an analogous homogeneous phreatic sand tank aquifer and the corresponding inhomogeneous scale numerical models were established to investigate the groundwater flow under the combined influence of artificial recharge (human activities) and decaying hydraulic conductivity (medium characteristics). In this study, groundwater flow through a managed aquifer recharge area in an alluvial fan was analyzed under the conditions of decaying hydraulic conductivity (K) with depth or length from apex to apron. The results showed that groundwater flow processes induced by artificial recharge were significantly controlled by the increasing decay exponents of K. The decaying K with depth or length in alluvial fan areas expanded the degree of influence of artificial recharge on groundwater flow. With the increase of decay exponents, the flow directions gradually changed from a horizontal to vertical direction. Groundwater age and spatial variability could also be increased by the increasing decay exponents. The residence time distributions (RTDs) of ambient groundwater and artificially recharged water exhibited logarithmic, exponential, and power law behavior. Penetration depth and travel times of ambient groundwater flow could be affected by artificial recharge and decay exponents. Furthermore, with the increase of decay exponents, the thickness of the artificially recharged water lens and travel times of artificially recharged water were increased. These findings have important implications for the performance of managed aquifer recharge in alluvial fan areas as well as the importance of considering the gradual decrease of K with depth and length.

Groundwater potential recharge areas delineation using groundwater potential recharge index (GPRI) within arid areas: Ghomrassen, south Tunisia

The Ghomrassen region is located in southern Tunisia, which is an arid area where the annual rainfall does not exceed 150 mm. This region suffers from water table drawdown and scarcity of surface water. Groundwater is of strategic importance to meet the population and economic needs. Groundwater recharge estimation and fundamental controlling factors assessment were utmost importance solutions for sustainable groundwater management and groundwater protect. This study aims to assess the main factors controlling groundwater recharge and delineate potential recharge area of Ghomrassen aquifer. To achieve this objective, a groundwater potential recharge index (GPRI) was computed using five parameters such as soil lithology, land use/cover, lineament density, slope, and drainage density. For each parameter a score and weight were assigned and thematic maps were developed. The results indicate that about 35% of the study area is designated as excellent potential recharge, whereas 18% of study shows a moderate recharge and lower potential recharge covers 47% of study area. A potential groundwater recharge of Ghomrassen aquifer was estimated is about 5.4 Mm3.y−1. The results show that the most favorable areas for recharging are the upstream part formed by fractured and fissured rocks and the central part of the Ghomrassen basin formed by recent alluvium. The presented GPRI methodology can be helpful for the planning of various water projects locations of artificial recharge structures and wells establishment.

Hydrological modeling in a basin of the Brazilian Cerrado biome

The Brazilian Cerrado biome (BCB) is among 25 biodiversity hotspots identified worldwide, and covers the recharge area of important aquifers and rivers in South America. The increase in deforestation has been threatening water availability in this region. In order to assist in the water-resource management of the BCB, this study models the daily streamflow in a basin of the Cerrado, using two approaches: a process-based model (Soil and Water Assessment Tool - SWAT) and the data-driven model (Artificial Neural Network - ANN). The performance of the models was evaluated by the Nash-Sutcliffe coefficient (NSE), coefficient of determination (R2) and flow-duration-curves (FDC). The results indicate that SWAT (NSE > 0.61; R2 > 0.68) and ANN (NSE > 0.91; R2 > 0.79) models are suitable tools in daily streamflow modeling of the studied basin, with the ANN model being the most accurate. Based on FDC, the ANN model was also better than the SWAT model for all frequencies evaluated. Thus, the ANN model is a promising new approach for daily streamflow modelling in this region. Moreover, the results of this study can help water-resource managers in planning and implementing appropriate water allocation and conservation measures in the Brazilian Cerrado biome.

Water infiltration rate in the soil under different uses and covers in the Poxim River basin, Sergipe, Brazil

Watersheds are units of planning and environmental management having a great importance in the management of water resources and their use. To this end, knowledge about the soil's physical and water attributes is of paramount importance in the context of water dynamics in aquifer recharge areas. Water infiltration rate into the soil is considered an important variable in the hydrological cycle, as the increase in this process can lead to a reduction in erosion and consequently greater groundwater recharge. Thus, the present work aimed to evaluate the soil water infiltration rate in the phytophysiognomy of the Poxim River basin in the State of Sergipe, in the agriculture, eucalyptus and forest areas, and to observe the effect of the infiltration water rate in areas of no-till, minimum and conventional cultivation. The soil water infiltration rate was obtained through the use of double cylinder infiltrometer and estimated through the mathematical models of Kostiakov, Kostiakov-Lewis, Horton and Philip. When making comparisons between the models for estimating of soil water infiltration rates, the Horton model showed a better fit compared to the other models used, and the type of soil cover that obtained the highest infiltration rate was the forest. No-till areas provided higher water infiltration rates in the soil, contributing to greater groundwater recharge.

The Mixing Regime and Turbidity of Lake Banyoles (NE Spain): Response to Climate Change

This study analyses the water temperature changes in Lake Banyoles over the past four decades. Lake Banyoles, Spain’s second highest lake, situated in the western Mediterranean (NE Iberian Peninsula). Over the past 44 years, the warming trend of the lake’s surface waters (0.52 °C decade−1) and the cooling trend of its deep waters (−0.66 °C decade−1) during summer (July–September) have resulted in an increased degree of stratification. Furthermore, the stratification period is currently double that of the 1970s. Meanwhile, over the past two decades, lake surface turbidity has remained constant in summer. Although turbidity did decrease during winter, it still remained higher than in the summer months. This reduction in turbidity is likely associated with the decrease in groundwater input into the lake, which has been caused by a significant decrease in rainfall in the aquifer recharge area that feeds the lake through groundwater sources. As a unique freshwater sentinel lake under the influence of the climate change, Lake Banyoles provides evidence that global warming in the western Mediterranean boosts the strength and duration of the lake’s stratification and, in response, the associated decrease in the turbidity of its epilimnion.

An Attempt to Characterize the Recharge of Alluvial Fans Facing the Northern Italian Apennines: Indications from Water Stable Isotopes

Nowadays, climate changes and increased water demand for human and agricultural purposes pose important questions for the groundwater management of alluvial aquifers facing the northern Italian Apennines. The large groundwater withdrawals, coupled with an overall worsening of the water quality, requires a detailed knowledge of the recharge mechanisms of these aquifers that can be useful for further adaptation measures. Concerning the recharge area of the alluvial aquifers (i.e., apices made up of gravelly materials), the present study investigates a dataset made up of 282 water samples for which stable isotopes oxygen-18 (18O) and deuterium (2H) are available. The latter involves precipitations (three rain gauges), surface water (five rivers) and groundwater (twenty wells) from five selected alluvial fans. The study confirms that the different isotopic signatures characterizing rain and river water from this area can be exploited for preliminary characterization of their significance on groundwater recharge. These results lay the foundations for the further use of a suite of environmental tracers (in which a primary role is that of water stable isotopes) at the event-scale (i.e., that of rainfall and/or flood) for eventually estimating the effective quota of recharge linked to precipitation and surface water.

Karst Spring Recharge Areas and Discharge Relationship by Oxygen-18 and Deuterium Isotopes Analyses: A Case Study in Southern Latium Region, Italy

Karst aquifer recharge areas are usually difficult to identify because of the complexity of these aquifers’ characteristics. On the other hand, their identification is very important in the aim of protecting the groundwater resources that these aquifers host. Regarding this topic, this paper presents an approach aimed at identifying karst aquifer recharge areas by the application of oxygen-18 and deuterium isotopes composition of groundwater coupled with hydrological features. Oxygen-18 and deuterium isotope composition of Capodacqua di Spigno Spring, in the South of the Latium Region, has been applied with rainfall and discharge values related to the feeding aquifer of this spring. As δ18O and δ2H values of groundwater samples are natural tracers of the recharge area’s elevation, we propose a model, based on the distribution of the basin surfaces involved as recharge areas, in relation to elevations. The model estimates, for any discharge value, the percentage of the topographic area involved in the aquifer recharge. The setting up of this simulated distribution is supported by a Weibull cumulative probability function. The results show that the measured discharges increase as larger areas with lower elevations are involved in the recharge process.

Levantamento das características hidrodinâmicas dos aquíferos da bacia hidrográfica do Rio Anil, São Luís – MA

A água subterrânea é usada desde os primórdios das civilizações, e por razões naturais possui uma boa qualidade, o que se torna um atrativo para o usuário. Ademais, para um conhecimento profundo das condições hidrogeológicas de uma região é necessário conhecer suas propriedades hidrodinâmicas, desta forma, o trabalho teve como objetivo o levantamento das características hidrodinâmicas da bacia do rio Anil, e possuiu como base científica para o seu desenvolvimento a abordagem teórico-metodológica hipotético-dedutiva. A partir dos 30 poços tubulares do banco de dados de poços outorgados pela Secretaria de Meio Ambiente e Recursos Naturais – SEMA foi possível a elaboração dos mapas de isoietas de profundidade, nível estático, dinâmico de água subterrânea, rebaixamento e de vazão da bacia, dentre outras análises dos parâmetros hidrodinâmicos. Os resultados obtidos através da análise dos dados, destaca-se as médias: Profundidade 76,99 m, Nível Estático 16,80 m, Nível Dinâmico 28,52 m, Nível de Água 4,26m, Rebaixamento 11,72 m, Vazão 8,08 m³/h. Recomenda-se a implantação de políticas públicas voltadas para preservação das áreas de recarga de aquíferos na bacia hidrográfica do rio Anil e ressalta-se que a bacia e se encontra intensamente impermeabilizada por vários prédios, principalmente próximos das margens do rio, por conseguinte o controle e gerenciamento desse corpo hídrico é de fundamental importância para manutenção das reservas hídricas de qualidade.

Regional atmospheric dynamics govern interannual and seasonal stable isotope composition in southeastern Brazil

Climatic factors controlling seasonal and interannual changes of stable isotope composition in precipitation remains understudied across the tropics. Daily isotopic measurements of rainfall (2014–2017, Rio Claro, Southeast of Brazil) were used to identify the climatic factors governing the isotopic variability. Overall, precipitation presented large variations, ranging between −18.36‰ and +4.89‰ for δ18O, −136‰ to + 43.4‰ for δ2H, and −11.8‰ to +26.6‰ for d-excess. The Local Meteoric Water Line (δ2H = 8.05 ± 0.1·δ18O + 13.08 ± 0.5) indicated a strong influence of moisture recirculation along the transport of air masses. During the summer (wet season), high moisture content prevailed in the atmosphere. The latter was associated with recycled moisture from Amazonia region due to the influence of the South Atlantic Convergence Zone and Frontal Systems, resulting in depleted precipitation (δ18O ≤ −6‰). During the winter (dry season), the combination of Cold Fronts and minimal moisture transport from the Amazonia region, resulted in more enriched rainfall (δ18O ≥ −1‰). Atmospheric recirculation processes along the moisture pathway were also reflected on the seasonal d-excess variation. The strong correlation of δ18O and relative humidity along HYSPLIT trajectories confirmed the influence of regional atmospheric dynamics over isotopic composition of precipitation. Our findings provide new understanding of rainfall generation within the Guarani aquifer recharge area.

Potential recharge areas of deep aquifers: an application to the Vercelli–Biella Plain (NW Italy)

Deep aquifers typically serve as a key source of drinking water due to their good groundwater quality. Then the identification of deep aquifers recharge areas provides the local administration with a management tool to protect groundwater, through the implementation of legislative measures for the control of pollution sources. However, the location and size of recharge areas of deep aquifers are often difficult to define and generally require a large amount of data. The aim of this paper is to propose a method to identify potential recharge, throughflow and discharge areas of deep aquifers on a regional scale, due to their hydrodynamic features. As the proposed method identifies where deep-aquifer recharge can occur, but not the recharge rate, delimited areas are defined as “potential”. Particularly, the method analyses piezometric level differences between shallow and deep aquifers to understand groundwater flow direction. The areas where groundwater flow is downward are delimited as potential recharge areas of deep aquifers (PRADAs). The method represents a qualitative approach to the identification of PRADAs, because it permits to narrow down large plain areas extension, highlighting where potentially recharge areas are located. Then PRADAs location and shape can be defined effectively, expanding data sets and furthering analyses (hydrogeological reconstruction, hydraulic connectivity, hydro-chemical and isotopic methods…) in the identified areas. The hydrogeological setting investigated by this method is representative of many anthropized and groundwater-demanding plains around the world that require to be protected. Thus, the method represents a suitable approach for PRADAs’ identification in such settings, especially in low-income countries, where resource availability for studies and analyses is scarce. This method was then applied to a plain area of Northwest Italy, and the locations and sizes of potential recharge, throughflow and discharge areas of deep aquifers were identified on a regional scale.

Noble gas composition and 3H/3He groundwater ages in the Gardermoen Aquifer, Norway: Improved understanding of flow dynamics as a tool for water management

This study presents a novel data set of noble gas compositions and 3H/3He measurements in groundwater samples from the Gardermoen Aquifer in Norway. The motivation was to test the applicability of noble gases as tracers in constraining the conceptual model and improve the understanding of deeper parts of the aquifer. Flow models have been used as tools for water resource management at the Oslo international airport, which is located within the aquifer recharge area, and bordering towards protected nature reserves. Current models are well calibrated for upper parts of the aquifer, and in line with new noble gas data. However, in some areas large inverse pressure gradients are observed. Interpretation of noble gas data proved useful in understanding these pressure deviations as a result of water retention in low permeability layers of clay and silt. Noble gas composition, isotopic ratios and tritium water ages define different water “types”. Mixing along flow path or as a consequence of pumping were found to be indicators of geological heterogeneity, and were used to evaluate degree of flow separation as well as vertical versus horizontal flux. 3H/3He water ages varied between 0 and 50 years, increasing with depth below the groundwater table and along flow paths. These data indicate lower vertical permeability and longer residence times in deeper parts of the aquifer than suggested by previous models. This study is of high relevance in the continued water resource management scheme at Gardermoen, for improving existing models and in sound, long-term monitoring of groundwater, ensuring sustained influx towards sensitive biotopes.

Identifying Karst Aquifer Recharge Areas using Environmental Isotopes: A Case Study in Central Italy

Water resources management is one of the most important challenges worldwide because water represents a vital resource for sustaining life and the environment. With the aim of sustainable groundwater management, the identification of aquifer recharge areas is a useful tool for water resources protection. In a well-developed karst aquifer, environmental isotopes provide support for identifying aquifer recharge areas, residence time and interconnections between aquifer systems. This study deals with the use of environmental isotopes to identify the main recharge area of a karst aquifer in the Upper Valley of Aniene River (Central Italy). The analysis of 18O/16O and 2H/H values and their spatial distribution make it possible to trace back groundwater recharge areas based on average isotope elevations. The Inverse Hydrogeological Balance Method was used to validate spring recharge elevations obtained by the use of stable isotopes. Areas impacted by direct and rapid rainfall recharge into the study area were delineated, showing groundwater flowpaths from the boundaries to the core of the aquifer. The results of this study demonstrate the contribution that spatial and temporal isotope changes can provide to the identification of groundwater flowpaths in a karst basin, taking into account the hydrogeological setting.