Intergranular Aquifers Research Articles

Hydrodynamic study of karstic and intergranular aquifers using isotope geochemistry in Basara basin, Sulaimani, North-Eastern Iraq

The study area is located in the border of the high and low folded zone having a semi-arid climate area. This study initiated in 2009–2010, deals essentially with the investigation of the stable isotope (18O and deuterium 2H) as well as radioactive isotope represented by tritium 3H in rain, carbonate springs, intergranular aquifer, and surface water in order to investigate the source and relative ages of the groundwater and to show the influence of the altitude variations of the isotope composition. In this study and for the first time in the area, a local meteoric water line have been drawn with an empirical formula δ2H = 7.7δ18O + 14.4. The δ18O–altitude effect was determined using isotopic data for several samples taken from groundwater and surface water; it was approximated at −0.79 ‰/100 m for the entire area of the study. The output of the tritium concentrations in the springs and water well samples revealed to the conclusion that the values closely resembles to the present time tritium concentration in precipitation.

Integrated approach to delineation of drinking water protection zones

Protection of water resources plays an important role in providing safe and reliable drinking water for people and industry. Drinking water resource protection usually comprises active and passive measures. Passive measures, consisting of different protection zones surrounding the recharge area of the drinking water abstraction point, are the most important and most widely used measures. In the paper is illustrated how the protection of drinking water is implemented through the Water Framework Directive. Protection zones are defined based on the classification of drinking water resource types. They are divided into two groups; groundwater and surface water bodies. All of them are further divided into subgroups; groundwater into intergranular, karstic and fissured aquifers; surface water into stagnant and flowing water bodies. For all drinking water resources three protection zones are defined: inner, middle and outer zone. The outer zone was defined as the total recharge zone of the water quantities abstracted. Inside of inner zone, abstraction point zone is defined, which is protected from unauthorized access. Protection zones for intergranular aquifers are determined according to the isochrones based on travel times. Karstic aquifers are protected on the basis of intervention times and the level of the recharge zone karstification. Fissured aquifers are protected according to groundwater flow velocities; if the flow is laminar, the method of intergranular aquifers is used, otherwise the method of karstic aquifer is implemented. For surface water protection zones limitation method of distances, method of isochrones and dilution and method of intervention times are used.

Examining geological controls on baseflow index (BFI) using regression analysis: An illustration from the Thames Basin, UK

Summary Linear regression methods can be used to quantify geological controls on baseflow index (BFI). This is illustrated using an example from the Thames Basin, UK. Two approaches have been adopted. The areal extents of geological classes based on lithostratigraphic and hydrogeological classification schemes have been correlated with BFI for 44 ‘natural’ catchments from the Thames Basin. When regression models are built using lithostratigraphic classes that include a constant term then the model is shown to have some physical meaning and the relative influence of the different geological classes on BFI can be quantified. For example, the regression constants for two such models, 0.64 and 0.69, are consistent with the mean observed BFI (0.65) for the Thames Basin, and the signs and relative magnitudes of the regression coefficients for each of the lithostratigraphic classes are consistent with the hydrogeology of the Basin. In addition, regression coefficients for the lithostratigraphic classes scale linearly with estimates of log 10 hydraulic conductivity for each lithological class. When a regression is built using a hydrogeological classification scheme with no constant term, the model does not have any physical meaning, but it has a relatively high adjusted R 2 value and because of the continuous coverage of the hydrogeological classification scheme, the model can be used for predictive purposes. A model calibrated on the 44 ‘natural’ catchments and using four hydrogeological classes (low-permeability surficial deposits, consolidated aquitards, fractured aquifers and intergranular aquifers) is shown to perform as well as a model based on a hydrology of soil types (BFIHOST) scheme in predicting BFI in the Thames Basin. Validation of this model using 110 other ‘variably impacted’ catchments in the Basin shows that there is a correlation between modelled and observed BFI. Where the observed BFI is significantly higher than modelled BFI the deviations can be explained by an exogenous factor, catchment urban area. It is inferred that this is may be due influences from sewage discharge, mains leakage, and leakage from septic tanks.

“In situ” investigations to define the degradation of phenols in groundwater

Phenols are especially suitable for defining the mechanism of their degradation in groundwater. Phenols, for the most part, do not sorb on clastic aquifer material. This allows for a comparison of their relative concentrations in groundwater to the concentrations of a tracer, and leads to conclusions which can be drawn about the kinetics of phenol degradation. We have had an opportunity to monitor, in detail, the degradation of phenols at three locations. All three cases involved gravelly and sandy aquifers and aerobic conditions. A summary of the analytical methods applied, and basic results obtained is presented. This paper represents a short overview of the flow and results of the monitoring and five tests which were conducted at the three locations over several years. We believe that the results are representative of the behavior of phenols in aerobic intergranular aquifers.

Groundwater vulnerability assessment of the Cork Harbour area, SW Ireland

In the Cork Harbour area of SW Ireland, high yield karst and intergranular gravel aquifers are extremely vulnerable to pollution from a variety of sources, mainly due to the limited protection afforded by the thin cover of low permeability glacial and alluvial overburden. The main potential sources of pollution are due to rapid urbanisation of the Cork city area and its attendant infrastructure, and increased industrialisation in the area, with numerous new industries, particularly pharmaceutical and chemical industries, located around Cork Harbour. Other potential sources of pollution are a number of landfills in the area and an oil refinery near the mouth of Cork Harbour. Traditional agricultural sources of pollution also exist, due to increased use of chemical fertilisers. Finally, the susceptibility to saline intrusion of the karst and gravel aquifers around Cork Harbour is high due to the long coastline of the harbour and the low-lying nature of the karst synclines with their superimposed buried valleys.

Assessing the extent of induced leakage to an urban aquifer using environmental tracers: an example from Bishkek, capital of Kyrgyzstan, Central Asia

A groundwater residence time study of the deep fluvioglacial aquifer supplying Bishkek, capital of Kyrgyzstan, has found evidence of deep infiltration of recent recharge both in the main periurban wellfield and below the city. Commonly-employed hydrochemical markers detected urban influence in the city-centre to depths of 65–100 m, but gave no indication of the important role of induced river/canal bed leakage, either upgradient in the periurban wellfield or within the city. This was revealed by O and H stable isotope measurements, which showed that local rainfall/snowfall play little part in the aquifer water balance. More remarkably, the universal detection of CFCs and SF6, including in boreholes with 140–220 m deep upper screens, demonstrated that induced leakage of water just a few decades old had penetrated much deeper into the aquifer system than other hydrochemical markers indicated. A two-dimensional flow model set up to test whether such deep pumping-induced leakage could occur below the periurban wellfield confirmed its feasibility. The results imply vertical infiltration rates of 5–10 m/year and demonstrate that in this not-uncommon intergranular aquifer setting, deep boreholes with deep screen settings do not necessarily abstract old water. Hence, there are major implications for urban groundwater management and protection in such settings.

Springs on Ljubljana polje and Barje area, significant for quantity and quality condition of the groundwater body (Slovenia)

The intergranular aquifer of Ljubljana Field and the aquifer system of Ljubljana Moor are the most important sources of drinking water for Ljubljana. The springs that appear on the area of both groundwater bodies reflect the groundwater status, quantity and quality. The spring water in the Ljubljana Field appears on vowel change of the gravel terrace. We follow them in the lower part of Ljubljana Field aquifer from Fužine to confluence of rivers Sava and Ljubljanica. The spring water directly indicates the condition of groundwater level and the quality. On the Ljubljana Barje there are important springs on the Southern edge. These springs are crucial observation point for the quality and quantity status monitoring of the inflow fro main recharge area of Ljubljana Moor aquifers that are exploited for the water supply system By the detailed analysis of older sporadic measurements of springs in Ljubljana Polje and Ljubljansko barje we were able to assess the changes in theirs trends of quantity and to design the monitoring network of springs that would acquire adequate data for the actual and future assessment of quantity an quality of these groundwater bodies in the frame of all other available and representative observation points.

Thermal and mineral waters in north-eastern Slovenia

The Mura basin in north-eastern Slovenia is made up of two depressions, developed during the Late Neogene and Early Pliocene all within a widespread system of Pannonian basins. Both depressions are characterized by the occurrence of thermal waters of somewhat different hydrogeochemical character. Radgona depression is in the northern part of the basin and reaches depths of about 2 km. Thermal waters are generally dominated by sodium-bicarbonate, not related to the age of an aquifer, its wallrock composition, the type of porosity or total concentration of dissolved solids. Locally, sulphate-rich waters are encountered, and they are related to the presence of gypsum in the rocks of pre-Tertiary basement. The adjacent Ljutomer depression is over 4 km deep and comprises compartments with stagnant or semi-stagnant aquifers. Herein saline waters predominate, even in the aquifers of carbonate composition and abundant CO2 gas. In shallower, unconsolidated, intergranular aquifers sodium-bicarbonate waters predominate. Thermal aquifers of this type are very important to the economy of the region, but they are also subjected to overexploitation which is reflected in time-dependent changes of dynamic pressures, temperature, conductance, salinity, pH and concentration of major ions, trace elements, dissolved gasses, and total organic carbon. Mineral waters occur in shallow aquifers or springs in marginal areas of the Radgona depression. Bicarbonate waters are dominated by calcium, or both calcium and sodium. Some mineral waters are formed mainly by penetration of CO2 gas into shallow aquifers and consequent water–rock interaction. Composition of some mineral waters indicate their possible evolution from thermal waters which have risen from central parts of the Radgona depression along deep-seated faults, and have been modified by cooling and mixing processes.

In situ and laboratory investigations into contaminant migration

Predicting the spread of groundwater pollution demands a detailed understanding of the physical, chemical and microbial processes that control contaminant mobility in aquifers. Many field studies have been carried out around pollutant sources in an attempt to understand these processes, but quantitative results are often difficult to obtain because of the number of assumptions that have to be made about the flow regime or the source term which has given rise to the pollution. Models can be constructed with emphases on different processes to describe the known distribution of contaminants at any one time. However, if these models are to be used for predictive purposes, or to help remediation, it is important to identify and quantify individual processes precisely by independent or direct methods and not to rely on inference alone. Laboratory tests suffer from the fact that aquifer material has to be sampled and transferred to the laboratory. In the process, the sample may be disturbed physically thus altering its porosity, permeability and dispersive properties. It may be oxidised, thereby altering its chemistry, and the numbers, activity and character of any microbial population may change. In situ tracer experiments attempt to overcome the limitations of the laboratory by maintaining natural conditions, but at the same time allowing the injection of solute to be accurately defined and the hydraulic regime to be well controlled and monitored. Examples are given showing how integrated laboratory and field approaches have been used to study: (1) organic degradation in a pollution plume resulting from the disposal of industrial wastes and (2) the role of colloids in transporting radionuclides in an intergranular aquifer.

Relative Importance of Baseflow and Quickflow from Hydrographs of Karst Spring

AbstractEvaluation of recession hydrographs, from four karst springs in Europe, provides important information concerning the flow process operating in karst aquifer systems. Three analytic equations are used to evaluate the hydrographs: Mangin's equation, that assumes the recession is composed of both quickflow and baseflow; Coutagne's equation which considers the recession to be the response of a single reservoir; and a new function, Ht (which is derived from Coutagne's equation), that refers to the whole recession curve. Using Mangin's equation it is apparent that the saturated zone and thus baseflow exerts nearly complete control over the discharge of La Villa spring and is fairly important at Fuente Mayor and Baget springs, but is much less significant at Aliou spring. The saturated zone accounts for 100%, 90%, 91%, and 40% respectively for these springs. Using Coutagne's equation and Ht it is concluded that for Aliou and Baget springs, water flows freely in the high transmissive zones, but in the poorly transmissive zones, there is little continuity of connection in the system. At Fuente Mayor spring the differences in these zones are not so apparent and a gradual transition occurs. However, at La Villa spring, the karst aquifer is evidently much more homogeneous and the discharge is similar to that of a porous intergranular aquifer.

Geophysical methods application in groundwater natural protection against pollution

Natural protection against groundwater pollution mostly depends on water-bearing bed coverage with permeable rocks presenting a good or bad pollution intrusion barrier between the surface and subterranean water. Additional positive effects of polluted groundwater self-purification in these zones are visible. Natural protection from surface pollutants primarily depends on natural (geological) factors: (1) presence of poorly permeable rocks; (2) depth, lithology (grain-size distribution), and filtration features of rocks covering groundwater reservoirs; and (3) aquifer depth. In contrast to artesian aquifers, quantitative and qualitative evaluation for natural protection of intergranular aquifers with a free water surface is significantly complicated. In this case, the estimation is possible with the help of a specially developed statistical method, which requires the following elements referring to the zone of aeration: (1) poorly permeable strata depth; (2) filtration features; (3) groundwater level depth; and (4) lithology. For quantitative evaluation, it is necessary to know the time interval for pollution propagating from surface of the terrain to the free water surface. Describe access is particularly useful in the domain of zones of sanitary protection defined around the source of groundwater. This exploration method could be considerably rationalized by geophysical methods application. Various methods are useful, namely: electric mapping and sounding, self-potential method, seismic reflection and refraction methods, gravity and geomagnetic methods, the “turam” method, and different well-logging measurements (gamma ray, gammagamma, radioactivity log, and thermal log). In the paper, geophysical methods applictations in natural protection against groundwater pollution and appropriate critical analysis are presented. The results of this paper are based on the experience and application of geophysical methods to groundwater studies in Yugoslavia by the author.