Identification of a Holocene aquifer–lagoon system using hydrogeochemical data

The hydrogeochemical characteristics of the Cabo de Gata coastal aquifer (southeastern Spain) were studied in an attempt to explain the anomalous salinity of its groundwater. This detritic aquifer is characterised by the presence of waters with highly contrasting salinities; in some cases the salinity exceeds that of seawater. Multivariate analysis of water samples indicates two groups of water (G1 and G2). Group G1 is represented in the upper part of the aquifer, where the proportion of seawater varies between 10 and 60%, whilst G2 waters, taken from the lower part of the aquifer, contain 60−70% seawater. In addition, hydrogeochemical modelling was applied, which reveals that the waters have been subject to evaporation between 25 and 35%. There was a good agreement between the modelled results and the observed water chemistry. This evaporation would have occurred during the Holocene, in a coastal lagoon environment; the resulting brines would have infiltrated into the aquifer and, due to their greater density, sunk towards the impermeable base. The characteristics of this water enabled us to reconstruct the interactions that must have occurred between the coastal aquifer and the lagoon, and to identify the environmental conditions that prevailed in the study area during the Middle Holocene.     

Effects of sinuosity factor on hydrodynamic parameters estimation in karst systems: a dye tracer experiment from the Beyyayla sinkhole (Eskişehir,Turkey)

The sinuosity factor (SF) is a critical value in karst systems in terms of estimating their hydrodynamic parameters including groundwater velocity, coefficient of dispersion, etc., through dye tracer experiments. SF has been used in a number of different dye tracer experiments in karstic systems to estimate a representative flow path. While knowing SF is crucially important in the estimation of hydrodynamic parameters, its calculation is associated with significant uncertainty due to the complexity of subsurface karstic features. And yet, only a few studies have discussed its uncertainties, which might lead some errors in estimation of hydrodynamic parameters from dye tracer experiment. In this study, dye tracer experiments were conducted in two consecutive years (2003 and 2004) representing low and high flow conditions in the Beyyayla sinkhole (Eski?ehir, Turkey) where the flow path is well known. Uranine was used in experiments as a tracer and QTRACER computer program was used to determine the hydrodynamic properties of the Beyyayla karst system as well as to gain insights into the effects of SF from dye tracer experiments on estimated parameters. The results showed that the breakthrough curve follows a unimodal and a bimodal distribution in low and high flow conditions, respectively. These different distributions stem from the water transport mechanisms, where velocities were calculated as 58.2 and 93.6 m h^?1 during low and high flow conditions observed in a spring emerging from the south side of the studied system. The results also show that the coefficient of dispersion, Reynolds number, and Peclet number increased and longitudinal dispersivity decreased with the higher flow rate. Furthermore, the estimated parameters did not vary with either the flow conditions or the tracer transit time, but they have shown some variations with SF. When SF was increased by 50 %, a change in these parameters was obtained in the range of 50–125 %.     

Modeling the Neuman’s well function by an artificial neural network for the determination of unconfined aquifer parameters

An artificial neural network is designed as an improved alternative approach to the conventional type-curve matching technique for the determination of unconfined aquifer parameters. The network is implemented in a six-step protocol consisted of input selection, data splitting, design of network architecture, determination of network structure, network training, and network validation. The network is trained for the well function of unconfined aquifers by the back-propagation technique, adopting the Levenberg-Marquardt optimization algorithm. By applying a principal component analysis (PCA) on the training input data and through a trial-and-error procedure, the structure of the network is optimized with the topology of (3 × 6 × 3). The replicative, predictive, and structural validity of the developed network are evaluated with synthetic and real field data. The network eliminates graphical error inherent in the type-curve matching technique and provides an automatic and fast procedure for aquifer parameter estimation, particularly when analyzing many alternative pumping tests routinely obtained from continuous data loggers/data collection systems.     

PaPRIKa: a method for estimating karst resource and source vulnerability��application to the Ouysse karst system (southwest France)

The intrinsic vulnerability mapping method, PaPRIKa, is proposed as a common basis for karst groundwater protection in France. PaPRIKa is a specialized method for studying karst aquifers, derived from updating the RISKE and EPIK methods. Both the structure and functioning of karst aquifers are considered in order to develop a resource and source-vulnerability mapping method. PaPRIKa means Protection of aquifers from the assessment of four criteria: P for protection (considering the most protective aspects among parameters related to soil cover, unsaturated zone and epikarst behavior), R for rock type, I for infiltration and Ka for karstification degree. The Ouysse karst system, located in the Causses area in southwest France, is one of the nine pilot sites where this method was tested and standardized. The specificities of the Ouysse system such as the size of the catchment area, the spatial variability of the karst network development, the thick infiltration zone and the system??s dual character (both karst and non-karst areas), have provided a valuable field of application. The vulnerability of the resource was assessed for the entire catchment area, while source-orientated cartography was attempted for the catchment areas of the three different capture works used for drinking water.     

Drought impacts on long-term hydrodynamic behavior of groundwater in the tertiary–quaternary aquifer system of Shahrekord Plain, Iran

Shortage of water resources in arid and semi-arid areas causes water supply to be one of the most important subjects and major concerns within NGO and governments’ policies in recent years. The Shahrekord Plain aquifer system is located in a semi-arid area and acts as a key source of water supply. Groundwater management in this area is thus very important. Although change in the climatological factors is not possible, long-term fluctuation studies can help in managing the available water resources to overcome from drought or decrease its negative impact. The hydrodynamic study of the aquifer system coupled with the drought indices in each region can be useful in making decisions related to the hydro-ecosystem management of that region. In this article, hydrodynamics of the aquifer system of the Shahrekord Plain coupled with the ratio of P/PET as a drought index, are assessed on the long term. In Shahrekord Plain aquifer, there is a short-term seasonal fluctuation, which is increased by overexploitation during the dry season, when water is needed for irrigation. The hydrodynamic behavior of the plain aquifer on the long term is changing. This fluctuation at first is a function of time. Secondly, it is spatially dependent. Groundwater behavior is directly sensitive to the variation of drought index, both seasonally and on the long term.     

Review: “Jacob’s Zoo”—how using Jacob’s method for aquifer testing leads to more intuitive understanding of aquifer characteristics

The interpretation of aquifer responses to pumping tests is an important tool for assessing aquifer geometry and properties, which are critical in the assessment of water resources or in environmental remediation. However, the responses of aquifers, measured by time-drawdown relationships in monitoring wells, are nonunique solutions that are affected by many factors. Jacob’s Zoo is a collection of graphical interpretations that allows students and practitioners to develop an intuitive feel for how natural hydrogeological systems work, and develop a set of skills that provide a better understanding of aquifer properties far beyond interpretation of pumping tests. Jacob’s Zoo, based on the work of Jacob (1950), fosters a deeper understanding, although few practitioners realize the full utility of the method. Jacob CE (1950) Flow of groundwater, In: Rouse H (ed) Engineering Hydraulics, Wiley, New York. P 321–386.

     

Applications of Mango’s light hydrocarbon parameters to petroleum from Tarim basin,NW China

Light hydrocarbons in oils from the Tarim basin, NW China, were analyzed by GC. The light hydrocarbon parameters proposed by Mango revealed the distributions of the oils as two main types, marine and terrigenous sources. The Mango parameter K₁ not only displays a remarkable invariance (∼1) in most of the oils, but also shows significant variations (ranging from 1.20 to 1.54) in the oils occurring in the eastern part of the Tazhong Fault Uplift (EPTFU) located in the center of the Tarim basin. This variation of the K₁ value may indicate different petroleum systems in the areas which are superimposed in the EPTFU. Parameter K₂ proposed by Mango shows a significant variation between the two main oil types. The marine oils are characterized by relatively low values of K₂ (average 0.23) and the terrigenous oils by relatively high K₂ values (average 0.35), with general invariance within the same oil set. A plot of (P₃ + P₂ + N₂) vs. $(N_1^6)$ based on the model proposed by Mango can be used not only to discriminate between the two main genetic oils from the Tarim basin, but also to classify the marine oils from the Lunnan area into two sub-types, which may indicate two sub-petroleum systems existing in the area.     

Hydrogeochemical characterization and evolution of a regional karst aquifer in the Cuatrociénegas area,Mexico

The Cuatrociénegas area is useful for the investigation of the effect of groundwater extraction in the Chihuahuan freshwater xeric ecoregion. It has been investigated at this time using a selection of geochemical indicators (major, minor and trace elements) and δ³⁴S data, to characterize the origin of groundwater, the main geochemical processes and the mineral/groundwater interactions controlling the baseline geochemistry. The area is composed of limestones of Mesozoic age, with a composite thickness of about 500 m, overlaid by basin fill (poorly consolidated young sediments). Substantial water extraction and modification of natural discharges from the area along the last century have produced a detrimental impact on ecosystem structure and function. Water–rock interactions, mixing and evaporative processes dominate the baseline groundwater quality. Natural recharge is HCO₃–Ca type in equilibrium with calcite, low salinity (TDS?<?500 mg/L), Cl^? lower than 11 mg/L and average Li⁺ concentration of 0.005 mg/L. Along the groundwater flow systems, δ³⁴S evidence and mass transfer calculations indicate that Cretaceous gypsum dissolution and dedolomitization reactions adjust water composition to the SO₄–Ca type. The increase of water–rock interaction is reflected by Cl^? values increase (average 68 mg/L), TDS up to about 1500 mg/L and an average Li⁺ concentration of 0.063 mg/L. Calculations with chemical geothermometers indicate that temperature at depth could be at maximum of 15–20 °C higher than field-measured temperature for pozas. After groundwater is discharged to the surface, chemical evolution continues; water evaporation, CO₂ degassing and precipitation of minerals such as gypsum, calcite and kaolinite represent the final processes and reactions controlling water chemical composition.     

Quantification of groundwater–seawater interaction in a coastal sandy aquifer system: a study from Panama,Sri Lanka

The Panama coastal aquifer system is an important water resource in the southeast coast of Sri Lanka that provides adequate supplies of water for agriculture and domestic uses. One of the biggest threats to these fragile aquifers is the sea water intrusion. In this study, recharging mechanism and geochemical evaluation of groundwater in the coastal sandy aquifer of Panama were evaluated using chemical and stable isotope techniques. Thirty groundwater samples were collected and analyzed for their major ion concentrations and stable isotope ratios of oxygen (¹⁸O/¹⁶O) and hydrogen (D/H). All studied samples showed a ranking of major anions in the order Cl^? > HCO ₃ ^?  > SO ₄ ^2?  > N-NO₃ ^? while cations showed a decreasing order of abundance with Na⁺ > Ca²⁺ > Mg²⁺ > K⁺. Dominant groundwater hydrogeochemical types were Na–Cl and mixed Ca–Mg–Cl. Results of saturation index calculations indicate that the investigated groundwater body was mostly saturated with respect to calcite, dolomite and gypsum. In addition, stable isotope and geochemical data suggest that fresh groundwater in the aquifer is recharged mainly by local precipitation with slight modification from evaporation and saline water intrusions. Isotope data suggest that mixing of salt water with freshwater occurs in aquifers which are located towards the lagoon. Since the communities in the study area depend entirely on groundwater, an understanding of the hydrogeochemical characteristics of the aquifer system is extremely important for the better water resource management in the region.     

Groundwater supply and demand from southern Africa’s crystalline basement aquifer: evidence from Malawi

Failure of borehole sources in weathered and fractured crystalline basement aquifers in Malawi in southern Africa has been linked with poor borehole design, mechanical failure and badly sited boreholes. However, recent work in Malawi indicates that demand may now exceed long-term resource potential in some places and that this is also a cause of water point failure. An 11-year climate cycle (including a wet and dry period) necessitates overdraft from groundwater storage during the dry-cycle years before episodic rainfall events in the wetter part of the cycle again recharge the aquifers. Data, particularly groundwater hydrograph data, are sparse, but sufficient to evaluate the long-term renewable groundwater potential for both fractured and weathered basement-aquifer types in each of the 15 management areas in Malawi. The groundwater potential or long-term renewable resource (recharge) is given by the sum of Darcian throughflow and dry-season depletion of storage. Estimated rural demand exceeds the renewable resource in the fractured-rock aquifer in two management units and in the weathered-rock aquifer in two other units. Although there is inherent uncertainty in the water-balance estimates, the likelihood that rural demand is exceeding long-term average recharge in some areas is cause for concern.     

Carbon isotope systematics of the Cambrian–Vendian aquifer system in the northern Baltic Basin: Implications to the age and evolution of groundwater

Groundwater in the Cambrian–Vendian aquifer system has a strongly depleted stable isotope composition (δ¹⁸O values of about −22‰) and a low radiocarbon concentration, which suggests that the water is of glacial origin from the last Ice Age. The aim of this paper was to elucidate the timing of infiltration of glacial waters and to understand the geochemical evolution of this groundwater. The composition of the dissolved inorganic C (DIC) in Cambrian–Vendian groundwater is influenced by complex reactions and isotope exchange processes between water, organic materials and rock matrix. The δ¹³C composition of dissolved inorganic C in Cambrian–Vendian water also indicates a bacterial modification of the isotope system. The corrected radiocarbon ages of groundwater are between 14,000 and 27,000 radiocarbon years, which is coeval with the advance of the Weichselian Glacier in the area.     

Gender myth and the mind-city composite: from Plato’s Atlantis to Walter Benjamin’s philosophical urbanism

In the early twentieth century Walter Benjamin introduced the idea of epochal and ongoing progression in interaction between mind and the built environment. Since early antiquity, the present study suggests, Benjamin’s notion has been manifest in metaphors of gender in city-form, whereby edifices and urban voids have represented masculinity and femininity, respectively. At the onset of interaction between mind and the built environment are prehistoric myths related to the human body and to the sky. During antiquity gender projection can be detected in western perceptions linking natural and built environments, commencing with Plato’s Atlantis and his Myth of Er, and later as a likely import of the Chinese yin-yang mythology. Culminating with the Age of Discovery, alongside advances in experiential awareness of the Earth’s sphericity, respective feminine and masculine earmarks can be detected in early modern perspicacity of the Earth’s southern and northern hemispheres. Our conceptions of natural and built environments inherently continue to contain gender traits. Yet urban voids, as the feminine face of city-form, have been severely understated in the built environment. Through design and configuration of urban voids, allegories of femininity in city-form ought to be celebrated, not discarded.     

El Ni?o as a consequence of the global oscillation in the dynamics of the earth’s climatic system

During study of the physical nature and potential precursor features of the El Ni?o phenomenon in the Pacific, it was found that a negative large-scale temperature anomaly on the Indian Ocean surface may be one of its significant precursors. This anomaly appears prior to the occurrence of El Ni?o and is accompanied by growth in atmospheric pressure. It gradually extends eastwards along the equator until the zone of planetary convection in the area of the Indonesian Region. The west wind that emerges on the eastern peripherals of the mentioned pressure anomaly leads to reversal of the Pacific segment of the Walker equatorial atmospheric circulation and to a subsequent change in the zonal thermal dipole polarity in the tropical zone of the Pacific (the latter means culmination of the El Ni?o phenomenon). In addition to the mentioned thermobaric anomaly in the Indian Ocean, other obvious signs of large-scale pressure anomalies have been found in the global atmospheric pressure field; these anomalies may be interpreted as manifestations of the intradecadal global oscillation in the dynamics of the modern climatic system. It is suggested that the whole known complex of events related to the El Ni?o phenomenon in the Pacific is a consequence and a regional link of the planetary structure of this global atmospheric phenomenon.     

Thermal thickness of the Earth’s lithosphere: a numerical model

A technique is suggested and the thermal thickness of the lithosphere is calculated, as well as the temperature distribution in the lithosphere on the basis of data on topography, the age of the oceanic bottom, crustal composition and structure, gravity anomalies, and mean annual surface temperatures. The bottom of the lithosphere is determined as the 1300°C isotherm. The calculation resolution is 0.5°×0.5°. All first-order tectonic structures, such as mid-ocean ridges and plume areas in oceans, continental rifts, cratons, and orogenic belts, are expressed in the computed thermal thickness. The comparative analysis of the thermal thickness of oceanic and continental lithosphere, lithosphere of cratons and young platforms, ancient and young orogens, remnant oceanic basins and adjacent continental areas can be used in geodynamical analysis of the corresponding regions.     

Using impacts of deep-level mining to research karst hydrology—a Darcy-based approach to predict the future of dried-up dolomitic springs in the Far West Rand goldfield (South Africa). Part 1: a conceptual model of recharge and inter-compartmental flow

Some of the world’s deepest goldmines are located in the Far West Rand (FWR) goldfield operating below of up to 1.2-km-thick dolomites hosting some of the largest karst aquifers in South Africa. Associated impacts include the dewatering of the overlying karst aquifers as well as linking previously disconnected compartments by mining through aquicludes (dykes). The focus of the study is on predicting groundwater balances in re-watered aquifers after mining ceases as this will determine whether or not associated karst springs that dried-up due to dewatering will ever flow again. Critically revisiting, Swart et al. (Environ Geol 44:751–770, 2003a) who predict that all springs will flow again, this study uses significantly larger data sets and modified assumptions to increase the robustness of findings as the question is crucial for post-closure development. As a first of two papers, this part develops a conceptual model on the mega-compartment concept that predicts a flat water table across all linked compartments that would leave the springs dry. The model identifies the ratio between inflowing surface water (recharge) and underground water losses to downstream compartments via mined-through dykes (‘inter-compartmental groundwater flow’, IGF) as a key factor governing the elevation of the post-mining water table, creating the base for part 2, where the IGF and the post-mining water tables are determined using unique large data sets that have not been evaluated before.     

Pareto’s law and sample size: a case study of China’s urban system 1984–2008

While Pareto’s law has been widely supported by empirical evidence in urban studies, past studies have focused on finding best fits for city rank-size distribution. A main concern with Pareto’s law is the truncation of sample selection, for which few studies have examined it directly. This study tests three existing threshold methods (number threshold, size threshold, and urban population percentage threshold) using China’s city system as a case study. In addition, this study proposes a new method based upon the percentage threshold of the total number of cities. A systematic analysis is applied to examine the relationship between Pareto exponent and sample size using different threshold methods. The results show that Pareto exponent is sensitive to sample size and the truncation point. Including only large cities is problematic because a slight change in the truncation point will yield quite different results of Pareto exponent. In addition, the new method, the percentage threshold of the total number of cities method, presents an advantage over previous methods, in that this method yields a consistent set of results over a wide range of thresholds. Finally, when using this new method with China’s city system, the Pareto exponent presents a turning point in 1996, representing China’s transition from a planned economy to a more market oriented economy during that period.     

Impacts of the carbon emission trading system on China’s carbon emission peak: a new data-driven approach

Natural Hazards - Over the past four decades, China’s extensive economic growth mode has led to substantial greenhouse gas emissions, and China has become the world’s largest emitter...     

Multi-tracer tests to evaluate the hydraulic setting of a complex aquifer system (Brévilles spring catchment, France)

For good management of groundwater resources, and to comply with European and national regulations, a detailed understanding of an aquifer’s hydraulic setting is required. In order to better characterize a sandy aquifer that is affected by diffuse pollution (Brévilles spring catchment, Val d’Oise, France), and to quantify the transfer time in the saturated zone, a multi-tracer test involving a new technique, the ‘finite volume point dilution method’, has been performed in natural flow conditions. In November 2005, injections of four different tracers took place in four piezometers involving different locations and depths in the aquifer. Recovery of the tracers was observed at two different places near the aquifer outlet. A particularly long and unusual monitoring exercise (27 months) demonstrated the existence of several different velocities within the sandy layer, which seems to be linked to the decrease of hydraulic conductivity with depth. The new insight and parameter quantification brought by interpretation of these tests contribute to a better characterization of the saturated zone. The particularly long-term monitoring exercise also gives new information to understand and forecast the trend and persistence of groundwater contamination by pesticides in the catchment.