Behavior Of Aquifer Research Articles

Hydrological system behaviour of an alluvial aquifer under climate change

In this paper, we present an assessment of the sensitivity of groundwater-surface water interactions to climate change in an alluvial aquifer, located in the Ljubljansko polje, Slovenia. The investigation is motivated by a recent assessment of climate change pressures on the water balance in the Sava River Basin (Gampe et al., 2016). The assessment was performed using a comprehensive hydrological modelling approach, which is based on the direct/indirect communication between FEFLOW and WaSiM/MIKE 11. This modelling framework provides a precise simulation of the critical processes in the study domain, which are the main drivers influencing the interactions between precipitation, river water and groundwater under different future climate scenarios. Climate projections were based on the results of the three regional climate models SMHI-RCA4, KNMI-RACMO22E and CLMcom-CCLM4. The results show that there will be higher levels of local precipitation during 2036–2065, the projected river discharge will be larger in the future compared to 2000–2014, and it is unlikely that the Ljubljansko polje will suffer from water scarcity. In addition, amongst the various sections of the Sava River the section between Črnuče and Šentjakob is the one most sensitive to climate change. By running the models under different climate scenarios a deeper insight into aquifer system functioning was obtained. Investigating impacts of climate change on groundwater and interactions between surface water and groundwater on the local scale is a basis for applying such a study on the global scale, which was still not very well investigated.

Validating the KAGIS black‐box GIS‐based model in a Mediterranean karst aquifer: Case of study of Mela aquifer (SE Spain)

AbstractKarst Aquifer GIS‐based model (KAGIS model) is developed and applied to Mela aquifer, a small karst aquifer located in a Mediterranean region (SE Spain). This model considers different variables, such as precipitation, land use, surface slope and lithology, and their geographical heterogeneity to calculate both, the run‐off coefficients and the fraction of precipitation which contributes to fill the soil water reservoir existing above the aquifer. Evapotranspiration uptakes deplete water, exclusively, from this soil water reservoir and aquifer recharge occurs when water in the soil reservoir exceeds the soil field capacity. The proposed model also obtains variations of the effective porosity in a vertical profile, an intrinsic consequence of the karstification processes. A new proposal from the Nash–Sutcliffe efficiency index, adapted to arid environments, is presented and employed to evaluate the model's ability to predict the water table oscillations. The uncertainty in the model parameters is determined by the Generalized Likelihood Uncertainty Estimation method. Afterwards, when KAGIS is calibrated, wavelet analysis is applied to the resulting data in order to evaluate the variability in the aquifer behaviour. Wavelet analysis reveals that the rapid hydrogeological response, typical of a wide variety of karst systems, is the prevailing feature of Mela aquifer. This study proves that KAGIS is a useful tool to quantify recharge and discharge rates of karst aquifers and can be effectively applied to develop a proper management of water resources in Mediterranean areas.

Integrated assessment of future potential global change scenarios and their hydrological impacts in coastal aquifers – a new tool to analyse management alternatives in the Plana Oropesa-Torreblanca aquifer

Abstract. Any change in the components of the water balance in a coastal aquifer, whether natural or anthropogenic, can alter the freshwater–salt water equilibrium. In this sense climate change (CC) and land use and land cover (LULC) change might significantly influence the availability of groundwater resources in the future. These coastal systems demand an integrated analysis of quantity and quality issues to obtain an appropriate assessment of hydrological impacts using density-dependent flow solutions. The aim of this work is to perform an integrated analysis of future potential global change (GC) scenarios and their hydrological impacts in a coastal aquifer, the Plana Oropesa-Torreblanca aquifer. It is a Mediterranean aquifer that extends over 75 km2 in which important historical LULC changes have been produced and are planned for the future. Future CC scenarios will be defined by using an equi-feasible and non-feasible ensemble of projections based on the results of a multi-criteria analysis of the series generated from several regional climatic models with different downscaling approaches. The hydrological impacts of these CC scenarios combined with future LULC scenarios will be assessed with a chain of models defined by a sequential coupling of rainfall-recharge models, crop irrigation requirements and irrigation return models (for the aquifer and its neighbours that feed it), and a density-dependent aquifer approach. This chain of models, calibrated using the available historical data, allow testing of the conceptual approximation of the aquifer behaviour. They are also fed with series representatives of potential global change scenarios in order to perform a sensitivity analysis regarding future scenarios of rainfall recharge, lateral flows coming from the hydraulically connected neighbouring aquifer, agricultural recharge (taking into account expected future LULC changes) and sea level rise (SLR). The proposed analysis is valuable for improving our knowledge about the aquifer, and so comprises a tool to design sustainable adaptation management strategies taking into account the uncertainty in future GC conditions and their impacts. The results show that GC scenarios produce significant increases in the variability of flow budget components and in the salinity.

Formation and transformation of chloroform during managed aquifer recharge (MAR)

Chlorination is an effective method to protect the safety of groundwater systems during managed aquifer recharge. However, chlorination leads to the formation of disinfection by-products, whose behavior in aquifers remains unclear and has caused public concern. In this study, an in-site test was performed on an anoxic aquifer in Shouguang City, China, to investigate the formation and transformation of chloroform during managed aquifer recharge. The field tests showed that the formation of chloroform in groundwater caused by the recharge of chlorinated water, and that the fate of chloroform was affected by adsorption and biodegradation. The retardation factor was 1.27, and the half-life was 29 days. The formation and transformation of chloroform during continuous recharge under different hydrochemical conditions was further investigated by batch experiments. These experiments showed that the formation of chloroform increased with contact time, tended to be stable after 10 h, and was facilitated by high chloride/TOC ratios, high pH, and low ionic strength (IS) for a given contact time. The adsorption experiments showed that the process accords with the pseudo-second-order kinetic equations and the Freundlich model. The adsorption capacity was pH dependent (1.01–1.66 μg/g at pH 5 and 2.17–3.05 μg/g at pH 9). Increasing the IS promotes adsorption. The results from biodegradation experiments indicated that the biodegradation was well fitted by the Monod equation. The retardation factor in the batch experiments was close to that of the field test, but the half-life was less than the field test. This is mainly due to the difference in the concentration of dissolved oxygen.

Hydrogeochemical behavior of an anthropogenic mine aquifer: Implications for potential remediation measures

This study characterizes the hydrogeochemical behavior of one of the most pollutant sources in the Iberian Pyrite Belt, namely, the Poderosa adit outflow. This artificial spring arises from an anthropogenic mine aquifer with a similar hydrogeological behavior to karstic systems, where the infiltration area is an endorheic zone and the aquifer shows allogenic recharge. Recent mining has markedly increased the contaminant levels. The pollutant load released from the adit to the receiving water body is very high, with average loads of 280 kg/day of Fe, 47 kg/day of Al, 17 kg/day of Cu and so on. However, a high variability is observed related to hydrological and geochemical factors, especially during intense rainy episodes. Thus, the pollutant load during these events suffers a dramatic increase, i.e., from ~100–200 kg/day of Fe during base flow to almost 2200 kg/day during the flow peak. These data highlight the importance of short but intense rainy events on metal fluxes from mining areas, which has been previously reported in surface waters but scarcely reported in mine adits, with expected lower response times to rainfall. The pollutant load released by non-point sources, i.e., spoil heaps, is lower than that released from the adit most of the year, although it increased noticeably during intense rainy events. Some remediation measures were adopted during the 1990s without a suitable hydrogeological characterization and were shown to be ineffective. On the basis of the obtained results, potential restoration measures are discussed.

Review: Micro-organic contaminants in groundwater in China

Micro-organic contaminants (MOs) in groundwater, which may have adverse effects on human health and ecosystems worldwide, are gaining increased attention in China. A great deal of research has been conducted to investigate their sources, occurrences and behavior in aquifers. This paper reviews the main sources, distribution, concentrations and behavior of a wide range of MOs in groundwater in China. These MOs include well-established persistent organic pollutants—polycyclic aromatic hydrocarbons (PAHs), hexachlorocyclohexanes (HCHs), polychlorinated biphenyls (PCBs), endocrine disrupting chemicals (poly brominated diphenyl ethers (PBDEs), phthalic acid esters (PAEs), bisphenol A (BPA)—and some contaminants of emerging concern such as pharmaceutical and personal care products (antibiotics, caffeine, shampoos) and perfluorinated compounds (PFCs). The results reveal that the main MOs in groundwater are PAHs, organochlorine pesticides (OCPs), PBDEs, PAEs, and antibiotics. Moreover, some PFCs such as perfluorobutane sulfonic acid (PFBS), perfluorobutanoic acid (PFBA) and perfluorooctanoic acid (PFOA) have only recently been observed in groundwater as emerging organic contaminants. Additionally, most MOs are distributed in populated and industrialized areas such as the southeast coast of China. Finally, industrial emissions, wastewater treatment plant effluents and agricultural wastewater are found to be dominant sources of MOs in groundwater. Based on the existing pollution levels, regulation and amelioration of MOs are warranted.

Spectral analysis of temporal non-stationary rainfall-runoff processes

This study treats the catchment as a block box system with considering the rainfall input and runoff output being a stochastic process. The temporal rainfall-runoff relationship at the catchment scale is described by a convolution integral on a continuous time scale. Using the Fourier-Stieltjes representation approach, a frequency domain solution to the convolution integral is developed to the spectral analysis of runoff processes generated by temporal non-stationary rainfall events. It is shown that the characteristic time scale of rainfall process increases the runoff discharge variability, while the catchment mean travel time constant plays the role in reducing the variability of runoff discharge. Similar to the behavior of groundwater aquifers, catchments act as a low-pass filter in the frequency domain for the rainfall input signal.

Modeling aquifer behaviour under climate change and high consumption: Case study of the Sfax region, southeast Tunisia

The water resources are exhausted by the increasing demand related to the population growth. They are also affected by climate circumstances, especially in arid and semi-arid regions. These areas are already undergoing noticeable shortages and low annual precipitation rate. This paper presents a numerical model of the Sfax shallow aquifer system that was developed by coupling the geographical information system tool ArcGIS 9.3 and ground water modeling system GMS6.5’s interface, ground water flow modeling MODFLOW 2000. Being in coastal city and having an arid climate with high consumption rates, this aquifer is undergoing a hydraulic stress situation. Therefore, the groundwater piezometric variations were calibrated for the period 2003–2013 and simulated based on two scenarios; first the constant and growing consumption and second the rainfall forecast as a result of climate change scenario released by the Tunisian Ministry of Agriculture and Water Resources and the German International Cooperation Agency “GIZ” using HadCM3 as a general circulation model. The piezometric simulations globally forecast a decrease that is about 0.5 m in 2020 and 1 m in 2050 locally the decrease is more pronounced in “Chaffar” and “Djbeniana” regions and that is more evident for the increasing consumption scenario. The two scenarios announce a quantitative degradation of the groundwater by the year 2050 with an alarming marine intrusion in “Djbeniana” region.

Improved Characterization of Groundwater Flow in Heterogeneous Aquifers Using Granular Polyacrylamide (PAM) Gel as Temporary Grout

AbstractThe range of options for investigation of hydraulic behavior of aquifers from boreholes has been limited to rigid, cumbersome packers, and inflatable sleeves. Here we show how a new temporary borehole sealing technique using soft grains of polyacrylamide (PAM) gel as a sealing material can be used to investigate natural groundwater flow dynamics and discuss other possible applications of the technology. If no compressive stress is applied, the gel packing, with a permeability similar to open gravel, suppresses free convection, allowing for local temperature measurements and chemical sampling through free‐flowing gel packing. Active heating laboratory and field experiments combined with temperature measurements along fiber optic cables were conducted in water‐filled boreholes and boreholes filled with soft grains of polyacrylamide gel. The gel packing is shown to minimize the effect of free convection within the well column and enable detection of thin zones of relatively high or low velocity in a highly transmissive alluvial aquifer, thus providing a significant improvement compared to temperature measurements in open boreholes. Laboratory experiments demonstrate that under modest compressive stress to the gel media the permeability transitions from highly permeable to nearly impermeable grouting. Under this configuration the gel packing could potentially allow for monitoring local response pressure from the formation with all other locations in the borehole hydraulically isolated.

Treshold-controlled three-stage hydraulic behaviour of a mantled shallow carbonate aquifer (Tuhala karst area, North Estonia)

As karst aquifers are often characterised by non-linear behaviour, ascertaining the turning points in their hydraulic regime may provide essential information on the functioning of the aquifer. These characteristics also apply to the Silurian-Ordovician aquifer system, composed of diverse carbonate rocks, in Estonia. The aquifer system is an important source of drinking water in northern Estonia. It also comprises the Nabala- Rakvere aquifer, a locally important groundwater resource that underlies the Tuhala karst area famous for an intermittently overflowing karst spring known as the Witch's Well. The water rich in humic substances of the Tuhala River recharges the Tuhala karst system, which is drained by two spring groups. In order to develop measures for the sustainable management of the aquifer in the future, the aim of this study was to enhance understanding of the hydraulic behaviour and hydrodynamic properties of the Tuhala karst system. From October 2014 to December 2016 an extensive field campaign was carried out comprising the observation of 22 surface- and groundwater monitoring points for water level and physico-chemical parameters and the performance of four quantitative tracer tests. The data obtained were evaluated in accordance with the input� output water level relation curves and a conceptual model of the system was set up. The results show that a strong hydraulic link exists, primarily through well-developed conduits between the recharge and discharge area of the karst system. Depending on the hydrological conditions, groundwater flow direc tions vary and maximum linear flow velocities range between \~225 and 800 m/h. A threshold-controlled throughput capacity and interaction with the adjacent aquifer cause imbalances between the input and output discharges of the karst system. Tracer tests coupled with surface and groundwater level relation curve analysis allowed the specification of flow threshold conditions for the Witch's Well spring group and the overflow threshold for the Witch's Well, among other key hydrological events. The hydraulic regime of the karst system was divided into three stages, each with differing threshold controls and hydrodynamic characteristics. Key words: karst system, shallow carbonate aquifer, monitoring, tracer test, water level relation curve, threshold, overflow.  Dolo\vanje mejnih vrednosti tristopenjskega hidravlji\vnega obna\vanja pokritega plitvega karbonatnega vodonosnika (Tuhalski kras, severna Estonija) Kra\vki vodonosniki se pogosto obna\vajo nelinearno, zato lahko z ugotavljanjem mejnih vrednosti v hidravli\vnem re\vimu zagotovimo bistvene informacije o delovanju vodonosnika. To velja tudi za silurijsko-ordovicijski vodonosni sistem v Estoniji, ki ga sestavljajo razli\vne karbonatne kamnine in je pomemben vir pitne vode na severu dr\vave. Vklju\vuje tudi vodonosnik Nabala- Rakvere, ki je lokalno pomemben vodni vir. Na tem obmo\vju se nahaja Tuhalski kras, ki je znan po ob\vasno bruhajo\vem kra\vkem izviru Witch's Well (\varovni\vin vodnjak). Tuhalski vodonosnik napaja reka Tuhala, bogata z huminskimi snovmi, prazni pa se skozi dve skupini izvirov. Da bi v prihodnje razvili ukrepe za trajnostno upravljanje vodonosnika, je bil namen te raziskave izbolj\vati razumevanje hidravli\vnega obna\vanja in hidrodinami\vnih lastnosti kra\vkega sistema. Od oktobra 2014 do decembra 2016 smo opravili obse\vno terensko delo, ki je obsegalo spremljanje vodostajev in fizikalno-kemijskih parametrov v 23 povr\vinskih in podzemnih to\vkah ter izvedbo \vtirih kvantitativnih sledilnih poskusov. Pridobljene podatke smo ovrednotili na podlagi krivulje odvisnosti vhodnih in izhodnih vodnih nivojev. Vzpostavili smo konceptualni model sistema. Rezultati ka\vejo na obstoj mo\vne hidravli\vne povezave predvsem z dobro razvitimi kanali med obmo\vji napajanja in praznjenja kra\vkega sistema. Odvisno od hidrolo\vkih razmer se spreminjajo smeri in hitrosti toka podzemne vode, ki zna\vajo od \~225 do 800 m/h. Kapaciteta prepustnosti, ki jo uravnavajo dolo\vene mejne vrednosti, in posledi\vne in terakcije s sosednjimi vodonosniki povzro\vajo neravnovesja med vhodnimi in izhodnimi preto\vnimi vrednostmi kra\vkega sistema. Zdru\vevanje rezultatov sledilnih poskusov z analizo krivulje odvisnosti povr\vinskih in podzemnih vodostajev nam je omogo\vilo, da smo dolo\vili mejne preto\vne vrednosti izvira Witch's Well in druge klju\vne hidrolo\vke dogodke. Hidravli\vni re\vim kra\vkega sistema smo razdelili na tri faze, od katerih ima vsaka dolo\vene mejne vrednosti in hidrodinami\vne lastnosti. Klju\vne besede: kra\vki sistem, plitvi karbonatni vodonosnik, monitoring, sledilni poskus, krivulja odvisnosti vodnih nivojev, prag, preliv.

Climatological trends and anticipated karst spring quantity and quality: case study of the Slovene Istria

Abstract The behaviour of aquifers with karst porosity is dependent on hydrological conditions. This is due to the peculiar characteristics of the groundwater flow and dynamics of hydrological processes in karst. As a result, karst aquifers are especially vulnerable to the effects of environmental change. We assessed the long-term climatological and hydrological trends and the short-term effects of increasingly frequent extreme hydrological events (droughts) for the Mediterranean karst spring Rižana in SW Slovenia. The findings predict higher mean annual air temperatures of 0.34°C decade −1 , lower annual precipitation of c. 60 mm decade −1 and higher annual actual evapotranspiration (especially during spring and summer) of 32–49 mm decade −1 . As a consequence, we can expect a decrease in the mean annual discharge of the spring of c. 480 l s −1 decade −1 with prolonged dry summer periods. Detailed monitoring of the physical, chemical and microbiological parameters showed that the flood pulses caused by precipitation events after a long dry period cause a significant deterioration in water quality. In such situations, contaminants stored in the unsaturated zone are flushed out and counts of coliform bacteria can reach >1400 cfu (100 ml) −1 , with total Al and Fe concentrations up to 206 and 474 μg l −1 , respectively. These results suggest that there should be urgent adherence to water quality standards to protect karst water sources in view of the anticipated climatological stresses. Management strategies should promote monitoring and the rational use of karst water supplies.

Modelo Hidrogeológico Conceitual da Estação Ecológica de Santa Bárbara (EEcSB) em área do Sistema Aquífero Bauru (SAB)

A modelagem hidrogeológica possibilita responder várias questões capazes de descrever a variabilidade espacial e temporal do comportamento dos aquíferos, como as variações nos níveis, a direção e velocidade dos fluxos, a origem da água e volume disponível. A gestão das águas subterrâneas pode ser beneficiada pelas informações geradas pela construção de um Modelo Hidrogeológico Conceitual (MHC), buscando maximizar os dados e experiências, utilizando ambos de forma sistemática para obtenção de respostas e conhecimentos sobre a dinâmica das águas subterrâneas. Este estudo teve como objetivo construir um MHC utilizando técnicas de análise espacial aplicadas a variáveis ambientais e dados de nível freático. Buscou-se com a utilização de uma metodologia quantitativa e qualitativa gerar um MHC para descrever a dinâmica do Sistema Aquífero Bauru (SAB) na Estação Ecológica de Santa Bárbara (EEcSB), município de Águas de Santa Barbara/SP. Os resultados forneceram um MHC que permite uma serie de interpretações iniciais sobre o comportamento do escoamento subterrâneo, subsidiando a tomada de decisões para proteção dos recursos hídricos nos limites da EEcSB. Conclui-se que as descargas por fluxos subterrâneos recentes abastecem as drenagens superficiais presentes na área e este fluxo subterrâneo acompanha a topografia em direção às drenagens principais.

Hydrogeochemical characterization of water mineralization in Tebessa-Kasserine karst system (Tuniso-Algerian Transboundry basin)

Carbonate aquifers provide large parts of the water supply for more than a quarter of the world’s population. The geochemical assessment of these heterogeneous aquifers is a valuable endeavor to ensure a rational management and protection of groundwater resources. To secure its durability, regard to increasing water demands and climate challenges make the problem of prevalence of water scarcity, vulnerability, and drought conditions extremely complicated. In Tebessa–Kasserine basin (Tuniso-Algerian international border), karst aquifers are receiving increasing interest, as the area has typical karst landscape and the hydrogeological system mostly consists of carbonates formation. Thus, a thorough understanding of aquifer behavior and water mineralization origin using geochemical and statistical tools can lead to relevant information regarding karst processes, groundwater chemistry, and protection. Subsequently, this study represents a pioneer baseline of the hydrogeochemical characterization of karst features in this international border area and it aims to identify the origin of karst water mineralization, its spatial distribution, and factors influencing water composition. The hydrogeochemical assessment of the sampled waters shifts from low mineralized Ca-HCO3 waters to Ca-SO4 and Na–Cl water types. TDS values range from 10 to 490.66 mg/l. A Gibbs diagram indicates that karst waters have been recently recharged by direct rainfall infiltration. Water quality gets modified along pathways and dissolution, formations weathering, and ion exchange processes seem to be the predominant geochemical factors influencing water mineralization. The PCA confirms the spatial variability of water types and indicates that it largely depends on aquifer lithology and on geographical position of water points.

Temporal dependence of potentiometric levels and groundwater salinity in alluvial aquifer upon rainfall and evapotranspiration

ABSTRACT Rainfall uncertainty and high evapotranspiration rates in the semiarid regions not only play an important impact on surface water scarcity, but interfere on shallow groundwater quantity and quality. The aim of this study was to apply geostatistical methodology to analyze the time dependence of potentiometric levels and groundwater salinity in an intensively monitored alluvial aquifer upon agroclimatological variables, and thus investigate possible monthly and annual correlations. Statistically stable piezometers were considered for the temporal analysis, representing the mean behavior of the whole aquifer. It has been verified that stable piezometers for groundwater levels exhibited temporal dependence of 7 months, similar to the temporal scale of variation for monthly precipitation and potential evapotranspiration, which is consistent to the resulting crossed-semivariogram. Meanwhile, stable piezometers for electrical conductivity showed high uncertainty on temporal dependence scale, which ranged from 3 to 8 months. Thus, rainfall and evapotranspiration alone did not properly explain the temporal dynamics of groundwater salinity. The produced maps successfully identified the long term time pattern of groundwater variation, constituting an important support for water resources evaluation.

Spatial analysis of groundwater levels using Fuzzy Logic and geostatistical tools

The spatial variability evaluation of the water table of an aquifer provides useful information in water resources management plans. Geostatistical methods are often employed to map the free surface of an aquifer. In geostatistical analysis using Kriging techniques the selection of the optimal variogram is very important for the optimal method performance. This work compares three different criteria to assess the theoretical variogram that fits to the experimental one: the Least Squares Sum method, the Akaike Information Criterion and the Cressie’s Indicator. Moreover, variable distance metrics such as the Euclidean, Minkowski, Manhattan, Canberra and Bray-Curtis are applied to calculate the distance between the observation and the prediction points, that affects both the variogram calculation and the Kriging estimator. A Fuzzy Logic System is then applied to define the appropriate neighbors for each estimation point used in the Kriging algorithm. The two criteria used during the Fuzzy Logic process are the distance between observation and estimation points and the groundwater level value at each observation point. The proposed techniques are applied to a data set of 250 hydraulic head measurements distributed over an alluvial aquifer. The analysis showed that the Power-law variogram model and Manhattan distance metric within ordinary kriging provide the best results when the comprehensive geostatistical analysis process is applied. On the other hand, the Fuzzy Logic approach leads to a Gaussian variogram model and significantly improves the estimation performance. The two different variogram models can be explained in terms of a fractional Brownian motion approach and of aquifer behavior at local scale. Finally, maps of hydraulic head spatial variability and of predictions uncertainty are constructed for the area with the two different approaches comparing their advantages and drawbacks.

Water Wells Monitoring Using SCADA System for Water Supply Network, Case Study: Water Treatment Plant Urseni, Timis County, Romania

The water supply system in Timisoara Municipality is insured with about 25-30 % of the water demand from wells. The underground water headed to the water treatment plant in order to ensure equal distribution and pressure to consumers. The treatment plants used are Urseni and Ronaţ, near Timisoara, in Timis County. In Timisoara groundwater represents an alternative source for water supply and complementary to the surface water source. The present paper presents a case study with proposal and solutions for rehabilitation /equipment /modernization/ automation of water drilling in order to ensure that the entire system can be monitored and controlled remotely through SCADA (Supervisory control and data acquisition) system. The data collected from the field are designed for online efficiency monitoring regarding the energy consumption and water flow intake, performance indicators such as specific energy consumption KW/m3 and also in order to create a hydraulically system of the operating area to track the behavior of aquifers in time regarding the quality and quantity aspects.

Taking into Account the Role of the Weathering Profile in Determining Hydrodynamic Properties of Hard Rock Aquifers

The present study aims at understanding the role of the structure and the geometry of the weathering profile on the hydrodynamic behavior of hard rock aquifers. We first described 2D geophysical cross sections of weathering profiles realized and validated on an experimental site. Next, we implemented five long-term pumping tests in wells drilled at various locations of these cross sections. Finally, we chose the appropriate analytical solutions to determine the hydrodynamic parameters in consistence with the structure and the geometry of the weathering profile. Results reveal that land covers, weathering type and thickness, presence of no flow boundaries, etc. are all factors that explain the flow regime, which appears therefore much less unpredictable. In other words, the 2D geophysical data are enough to locate the best permeable areas, or the areas where the structure of the aquifer without impervious boundaries and with leakage favor a good long-term behavior of the well. The values of aquifer’s transmissivity vary between 5.10−3 and 4.10−5 m2/s. The storage varies between 0.06 and 7.10−7. The variability of these parameters from site to site reflects the high heterogeneity of hard rock aquifers.

Shale gas impacts on groundwater resources: Understanding the behavior of a shallow aquifer around a fracking site in Poland

Exploitation of shale gas by hydraulic fracturing (fracking) is highly controversial and concerns have been raised regarding induced risks from this technique. As part of the EU-funded SHEER Project, a shallow aquifer used for drinking water, overlying a zone of active shale-gas fracking, has been monitored for more than a year. Early results reveal the functioning of the shallow aquifer and hydrochemistry, focusing on the identification of potential impacts from the shale gas operation. This stage is an essential precursor to modeling impact scenarios of contamination and to predict changes in the aquifer.

Discharge and environmental isotope behaviours of adjacent fractured and porous aquifers

The combined use of hydrogeological and hydrogeochemical methods can provide relevant information about the characteristics of aquifers in studies focused on groundwater protection and management. In the present study, spring discharge monitoring coupled with stable and unstable water isotopes was used to compare the behaviour of adjacent fractured and porous aquifers hosted in a 4.5 km2 area along the same slope in the northern Apennines, Italy. Based on stable isotope analyses of four springs, a plausible local meteoric water line and a local vertical isotopic gradient were identified. Additionally, tritium contents revealed a recent meteoric origin for groundwater via infiltration in the area. The results of monthly stable isotope monitoring, hourly spring discharge monitoring, hourly rainfall monitoring, and statistical analyses (time series analysis) suggested that although the adjacent aquifers exhibited pronounced geological and hydrogeological differences, few discrepancies were observed regarding groundwater infiltration and release processes. Notably, they exhibited similar temporal delays associated with the response to precipitation events due to the roles of macro-fractures and macro-porosity. Groundwater circulation was characterized by piston and memory effects in both the fractured and porous aquifers, and these effects reflect the roles of micro-fractures/fissures and micro-porosity. The study highlights the relevant contributions of isotopes in studies that focus on spring vulnerability and aquifer processes. Moreover, results obtained in the Pietra di Bismantova site are useful to increase hydrological knowledge on the quite relevant aquifers hosted in Epi-ligurian rock slabs and the surrounding slope deposits in the northern Apennines of Italy.

Sustainability of intensive groundwater development: experience in Spain

Intensive aquifer development is common in arid and semiarid countries. The associated economic and social benefits are great, but management is needed and sustainability has to be analysed in the framework of a sound hydrogeological background which includes recharge as a key term. Recharge under natural conditions may greatly differ from the actual value under groundwater exploitation conditions when the aquifer is connected to surface water bodies or evaporation conditions are modified. Actual recharge is not an aquifer property but is variable depending on groundwater abstraction and its pattern, and changes in surface water-groundwater relationships and other circumstances, such as return irrigation flows, leakages, and activities to artificially modify it. Groundwater plays an important role in nature as it sustains spring flow, river base flow, wetlands, and crypto-wetlands, and the related provision of ecological services to mankind. Therefore, developable groundwater resources and their sustainability have to take into account concurrence and the net benefits of capturing it in a given moment and not in other circumstances, and exchanging groundwater-related nature services for the human use of groundwater. The often large storage relative to annual flow of aquifers implies that aquifer development produces effects that may last decades and even affect upcoming human generations. This new dimension, which has economic and sustainability aspects, is not as important for other water resources. Critical flow thresholds have to be considered for groundwater-dependent ecosystems. This is considered from the point of view of water quantity, which is the dominant aspect under arid and semiarid conditions. However, water quality may be as or more important for humans and for nature services, but this needs a separate treatment. The hydrogeological and socio-economic aspects of aquifer behaviour are presented taking into account the experience drawn from some intensively exploited and economically and socially important aquifers, mostly those in La Mancha, in central Spain, but also other intensively exploited Spanish aquifers. Top-down–down administrative decisions to get a given sustainable have resulted in partial failures, but if action is agreed among stakeholders better outcomes could be achieved. Mixed solutions seem the best approach.