Spring Catchment Area Research Articles

KARSYS hydrogeological 3D modeling of alpine karst aquifers developed in geologically complex areas: Picos de Europa National Park (Spain)

Karst aquifers are valuable groundwater resources whose management requires the use of functioning hydrogeological models. The KARSYS approach provides an explicit 3D conceptual model of the geometry and the functioning of karst aquifers that has been successfully applied in Swiss and Slovenian aquifers. In this work, KARSYS is applied in a complex geological area: the Picos de Europa National Park (Spain). The hydrogeological 3D model (500 km2) shows an alpine karst aquifer compartmentalized into 32 groundwater bodies dammed up by subvertical barriers creating elevated saturated zones (water tables at 1153 m asl) and lower ones (water tables at 145 m asl). The recharge is through 18 spring catchment areas. The groundwater flows to the saturated zones pass through vertical to inclined trajectories, and phreatic flows are oriented toward NW, NE and N. KARSYS can be applied to any geologically complex area at a regional scale, although the geological structure should be simplified and the precision in some places is low. Nevertheless, KARSYS helps to identify the hydrogeological behavior of karst areas and is a useful guide for future hydrogeological researches.

Karst spring catchment: an example from Dinaric karst

Definition of karst spring catchment or basin area and boundaries belongs to one of the greatest prob- lems of karst hydrology and hydrogeology, not adequately solved until now. This paper tries to address main problems in defining this crucial parameter. The theoretical aspect of this issue is discussed in the first two chapters. We have presented the example of the catchment area and bound- aries definition for the karst spring Zrnovnica catchment in Dinaric karst. Topographic catchment area of the Zrnov- nica Spring is 8.4 km 2 . The significant discrepancy in size of the hydrological-hydrogeological and topographical catchment is very common characteristic for the springs located in the karst areas. In the case of the Zrnovnica Spring, the hydrogeological catchment is at least seven times larger than topographic. Two following simple hydrological methods are used in order to calculate its hydrologic-hydrogeologic catchment: (1) the relationship between mean annual discharges and annual rainfall falling on the catchment, and (2) the Turc method. It is estimated that hydrogeologic catchment area of the Zrnovnica karst spring is much larger and very probably ranges between 60 and 80 km 2 . These values represent first rough assessment, which should be confirmed by more detailed interdisci- plinary investigations. According to the performed tracing tests, it seems that the catchment spreads on the north-east from the topographic catchment and that the Zrnovnica Spring karst aquifer is fed by groundwater overflow from the neighbouring more abundant karts spring Jadro.

Hydrogeological characterization of groundwater storage and drainage in an alpine karst aquifer (the Kanin massif, Julian Alps)

AbstractThe Kanin massif is an important trans‐boundary aquifer, which stretches between Slovenia and Italy. The groundwater is only partially exploited, mainly for water supply, but the aquifer exhibits great potential for future exploitation. Since no consistent regional overview of the hydrogeological functioning of the Kanin massif was available, the decision was made to perform a study of this area, using a pragmatic approach based on 3D geological and hydrogeological modelling. The so‐called KARSYS approach was applied, with the aim of characterizing the groundwater reserves within this karst massif and of locating the main drainage axes that carry groundwater from the recharge areas to the respective springs. Delineation of the catchment areas of the corresponding springs was carried out, and some new explanations were obtained, especially with regard to the Možnica spring, which is located in Slovenia and forms a potential source of drinking water. It was found that this spring's catchment area extends as far as the Italian ski resort of Sella Nevea. The conceptual model also provides a possible explanation about the underground drainage towards the Boka spring and waterfall, which has been a challenge for decades. This new explanation is based on the existence of a perched groundwater body that feeds the Boka spring via a system of conduits. Despite some limitations, the results, which consist of a visualization of the underground drainage and groundwater storage within the Kanin massif, can be used as a basis for planning the sustainable management of karst waters in the studied area. Copyright © 2014 John Wiley & Sons, Ltd.

Hydrogeological properties of a complex Dinaric karst catchment: Miljacka Spring case study

Miljacka is a karst spring situated in Dalmatia, Croatia. The interpretation of the Miljacka Spring catchment area boundary has repeatedly changed in the past, and the main conclusions of previous studies were that the spring, which is located in the Krka River canyon, receives all of its water from another karst river, Zrmanja. Here, we review a new hypothesis that the Miljacka Spring receives some of its water from the Krka River. It was not possible to verify the hypothesis by solely studying the geological composition, structural–tectonic relations and tracer test results. Therefore, a hydrochemical study was performed to confirm the hypothesis. By studying the geological composition, it was found that part of the catchment area of the Krka River is built of evaporites (gypsum and anhydrite), which are different in their mineral composition than carbonates, the usual rock mass of the Dinaric karst. The hydrochemical model was made using the NETPATH-WIN and PHREEQC software packages. The mixing model results confirmed the hypothesis that the Miljacka Spring waters come from both the Zrmanja (including smaller proportion of precipitation infiltrated directly in the karst aquifer) and Krka rivers. This case study shows the great importance of the application of hydrochemical investigations in karst hydrogeology, where research is often difficult due to the complexity of the groundwater system.

Assessment of the discharge regime and water budget of Belo Vrelo (source of the Tolisnica River, central Serbia)

A sufficiently long spring discharge regime monitoring data set allows for a large number of analyses, to better understand the process of transformation of precipitation into a discharge hydrograph. It is also possible to determine dynamic groundwater volumes in a karst spring catchment area, the water budget equation parameters and the like. It should be noted that a sufficiently long data set is deemed to be a continuous spring discharge time series of more than 30 years. Such time series are rare in Serbia. They are generally much shorter (less than 15 years), and the respective catchment areas therefore fall into the ?ungauged? category. In order to extend existing karst spring discharge time series, we developed a model whose outputs, apart from mean monthly spring discharges, include daily real evapotranspiration rates, catchment size and dynamic volume variation during the analytical period. So far the model has solely been used to assess the discharge regime and water budget of karst springs. The present paper aims to demonstrate that the model also yields good results in the case of springs that drain aquifers developed in marbles. Belo Vrelo (?White Spring?, source of the Tolisnica River), which drains marbles and marbleized limestones and dolomites of Cemerno Mountain, was selected for the present case study.

Influence of aquifer heterogeneity on karst hydraulics and catchment delineation employing distributive modeling approaches

Abstract. Due to their heterogeneous nature, karst aquifers pose a major challenge for hydrogeological investigations. Important procedures like the delineation of catchment areas for springs are hindered by the unknown locations and hydraulic properties of highly conductive karstic zones. In this work numerical modeling was employed as a tool in delineating catchment areas of several springs within a karst area in southwestern Germany. For this purpose, different distributive modeling approaches were implemented in the finite element simulation software Comsol Multiphysics®. The investigation focuses on the question to which degree the effect of karstification has to be taken into account for accurately simulating the hydraulic head distribution and the observed spring discharges. The results reveal that the representation of heterogeneities has a large influence on the delineation of the catchment areas. Not only the location of highly conductive elements but also their geometries play a major role for the resulting hydraulic head distribution and thus for catchment area delineation. The size distribution of the karst conduits derived from the numerical models agrees with knowledge from karst genesis. It was thus shown that numerical modeling is a useful tool for catchment delineation in karst aquifers based on results from different field observations.

Interpretation of hydrogeological functioning of a high karst plateau using the KARSYS approach: the case of Trnovsko-Banjška planota (Slovenia)

The high karst plateau of Trnovsko-Banjska planota is one of the most important reservoirs of karst water in Slovenia. Almost all important karst springs in this area are captured for water supply. A sustainable management of this source of groundwater is of strategic importance, not only as drinking water supply but also for the economy. For these reasons, many hydrogeological monitoring studies have been carried out over the last decades. However, no consistent regional overview of the hydrogeological functioning of Trnovsko-Banjska planota was available and we decided to study this area with more direct approach based on 3D geological and hydrogeological models. The so called KARSYS approach was developed in Switzerland and applied primarily to characterize groundwater reserves within a karst massif, and to sketch the main flow-paths carrying groundwater from recharge areas to the respective springs. The delineation of spring catchment areas in karst regions was better defined and interactions between catchments were interpreted. These results can be used to improve the management of karst waters in the studied area.

Definition of the river Gacka springs subcatchment areas on the basis of hydrogeological parameters

The river Gacka springs catchment area is located in the Dinaric karst, which is globally known as the locus typicus, or classical Karst. It is composed of four major and several minor karst springs of different discharge rates. The river Gacka springs are characterised by great discharge and exceptional quality, so the catchment area of the river is indicated in the Water Management Strategy (OFFICIAL GAZETTE NO. 91/08) as an area with strategically important eserves of drinking water for the Republic of Croatia. To determine the hydrogeological characteristics of he subcatchments of this large and complex aquifer system, hydrological and hydrochemical parameters were measured on the main springs. Data collected on the springs were analysed using the recession analysis by the „matching strip“ method, the statistical analysis of a time series of measured data both by autocorrelation (analysis of individual series) and by cross-correlation methods (analysis of interrelationships between time series), multivarilate statistical analysis (Factor Analysis) of hydrochemical parameters using the software package STATISTICA 6.0 (1998), and geochemical modelling of hydrochemical parameters using the NETPATH computer program. Interpretation of lithological, structural and tectonic characteristics of the rocks, together with tracing data and the applied analytical methods, allowed the springs catchment of the river Gacka to be divided into three subcatchments. The results of this study imply the necessity of a multidisciplinary approach to research.

Occurrence and spatial distribution of organic micro-pollutants in a complex hydrogeological karst system during low flow and high flow periods, results of a two-year study

Fifty-four different organic micro-pollutants (OMPs) including pharmaceuticals, pesticides, corrosion inhibitors and other typical wastewater compounds such as caffeine are repeatedly analyzed in approximately fifty groundwater observation points in a complex faulted and fractured carbonate aquifer system consisting of three spring catchment areas. With the applied HPLC–MS/MS method, achieving method quantification limits (MQL) of 1.2–28ngL−1, forty-four of the OMPs are detected in groundwater. Regarding the vertical distribution in the aquifer system the highest variety of OMPs occurs in the shallow aquifer.Most frequently detected compounds are atrazine together with the metabolites of several triazines, desethylatrazine (DEA) and desisopropylatrazine (DIA), the corrosion inhibitors 1H-benzotriazole and tolytriazoles and as pharmaceutical residues the anti-epileptic drug carbamazepine as well as the analgesic drug phenazone. Median OMP concentrations are in the range of 20–40ngL−1 with occasionally and locally higher concentrations of up to 6000ngL−1.Defined combinations of OMPs occur repeatedly in the same observation wells and allow to distinguish different input functions. The comparison of detection frequency with the number of prescribed doses gives information about the specific persistence of pharmaceuticals. The analgesic phenazone exhibits a peculiar high detection frequency, although it is recently not prescribed in significant amounts. The detection of the estrogen antagonist tamoxifen (6–17ngL−1) in a groundwater flow system is reported for the first time.

Caffeine as an indicator for the quantification of untreated wastewater in karst systems

Contamination from untreated wastewater leakage and related bacterial contamination poses a threat to drinking water quality. However, a quantification of the magnitude of leakage is difficult. The objective of this work is to provide a highly sensitive methodology for the estimation of the mass of untreated wastewater entering karst aquifers with rapid recharge. For this purpose a balance approach is adapted. It is based on the mass flow of caffeine in spring water, the load of caffeine in untreated wastewater and the daily water consumption per person in a spring catchment area. Caffeine is a source-specific indicator for wastewater, consumed and discharged in quantities allowing detection in a karst spring. The methodology was applied to estimate the amount of leaking and infiltrating wastewater to a well investigated karst aquifer on a daily basis. The calculated mean volume of untreated wastewater entering the aquifer was found to be 2.2 ± 0.5 m 3 d −1 (undiluted wastewater). It corresponds to approximately 0.4% of the total amount of wastewater within the spring catchment.

Hydrogeochemical and isotopic evidences for definition of tectonically controlled catchment areas of the Konavle area springs (SE Dalmatia, Croatia)

Increased human activities in the karst areas may result with unwanted impacts on environment, especially on groundwaters. This problem fostered reinterpretation of geological and hydrogeological relationships in the area of Konavle (SE Croatia). Detailed geological mapping enabled better insight into lithological and structural relationships in the area, especially concerning accumulation of groundwater in the karst underground of the hinterland. Thick succession of carbonate rocks of different permeability in the hinterland resulted in deep and complex reservoirs communicating mainly through tectonically predisposed zones. Aquifer dynamics is especially increased during the periods of high rainfalls and snow thawing in the hinterland. Four major springs, located along the tectonic contact between thick succession of Mesozoic carbonates and barrier composed of Palaeogene (and Neogene?) clastic rocks were observed. They show variable hydrogeochemical and isotopic values as a result of different altitudes, but also as a result of different catchment areas divided by important transversal fault systems. Since sporadically increased orthophosphate contents indicate anthropogenic influence presented preliminary results request careful monitoring and international cooperation to protect these sensitive transboundary catchment systems.

Vulnerability of the karst area related to potentially toxic elements

Soil samples from 31 locations in the Una river spring catchment were subject to chemical extraction analyses. The data were presented as distribution maps of potentially toxic elements (Al, Cu, Mn, Pb and Zn) in the surface soil of the area. To evaluate the vulnerability of the immediate spring zone of the karst catchment, the vulnerability map was derived from the application of the PI methodology proposed by the European COST Action 620. The PI method used to produce the vulnerability map takes into account the protective cover (P) and the infiltration conditions (I). It is based on the origin-pathway-target model. The π-factor (π = P ´ I) describes the vulnerability in the area, subdivided into 5 classes: π-factor in the range 0-1 implies an area of extreme vulnerability, while π-factor in the range 4-5 implies an area of very low vulnerability. The extraction procedure for the elements Al, Cu, Mn, Pb and Zn, has been applied in order to determine the potential mobility and redistribution of elements that could influence the groundwater and affect its quality. The applied extraction was the second step of the sequential procedure proposed by TESSIER et al. (1979), i.e. extraction with 1 mol dm-3 CH3COONa/CH3COOH buffer (pH 5). The results provide information on the potential mobility of the studied elements, indicating the possibility of their mobilization through changes in pH. Lead shows the greatest amount of mobility, with a mean of 9% (max. 16%) extracted under an acidic condition. Manganese follows with a mean of 5% (max. 11%) and zinc, copper and aluminium show less than 1% (mean) mobility. The vulnerability map of the karst area was produced in order to predict potential problem areas of karst aquifers. The Una spring catchment area presents generally low to moderate vulnerability; 8% of the studied area can be considered as extremely vulnerable according to the PI-methodology. Based on these data it was possible to delineate areas with a low protection cover i.e. combining the vulnerability map of the karst area with the distribution maps of potentially toxic elements, areas considered extremely vulnerable could be identified.

Effect of different land use/land cover on karst hydrogeochemistry: A paired catchment study of Chenqi and Dengzhanhe, Puding, Guizhou, SW China

Rainfall, spring stage, water temperature, pH and conductivity in the paired karst spring catchments of Chenqi and Dengzhanhe, which shared the same climatic condition but different land use/land cover (LULC) at Puding, Guizhou Province, SW China, were monitored by two high-resolution multi-parameter auto-recordable instrument of CTDP300 during the hydrological year of September 2007–September 2008. Other monthly hydrogeochemical and carbon isotopic (δ13C) variations in the paired karst catchments during the same hydrological year were also investigated. A thermodynamic model was used to link the continuous data to monthly hydrogeochemical data allowing the calculation of CO2 partial pressure (pCO2) and calcite saturation index (SIc) on a continuous basis. The primary study objective was to understand how the karst processes and karst hydrogeochemistry respond to different LULC, which is essential to assessing the karst-related carbon cycle. Marked seasonal and storm-scale variations were found for pH, conductivity, pCO2, SIc and δ13C of the two springs, indicating that both springs were dynamic and variable systems. However, there were differences in the magnitude and direction of the variations of these features between the two springs. The higher pCO2 and HCO3- concentration and lower pH, SIc and δ13C in Chenqi spring than those in Dengzhanhe spring tend to be related to the difference in LULC between Chenqi and Dengzhanhe spring catchments: in the Chenqi spring catchment, there was larger soil cover and the paddy land was located in the discharge area, both of which produced and kept more CO2 (a major driving agent for the karst processes) and lower δ13C in the soil-aquifer system, while in the Dengzhanhe spring catchment area, there was larger bare carbonate rock occurrence and the paddy land was located mainly in the recharge area. Moreover, the pH increased and pCO2 decreased generally in Chenqi spring after rainfall, possibly due to more carbonate dissolution in the larger soil cover rich in limestone fragments in the spring catchment, while the pH decreased and pCO2 increased generally in Dengzhanhe spring after rainfall. All these differences show that soil cover and land use pattern played important roles in the karst processes. In other words, the karst hydrogeochemistry and the karst-related carbon cycle could be regulated effectively by different LULC. In addition, the higher concentrations of Ca2+, SO42-, Mg2+ and conductivity of Dengzhanhe spring were due to the dissolution of more gypsum and dolomite minerals in the strata of Dengzhanhe spring catchment. Therefore, the karst hydrogeochemical parameters, including pH, conductivity, HCO3-, Ca2+, Mg2+, SO42-, pCO2, SIc, and δ13CDIC, could serve as good indicators of different LULC and the other environmental changes.

An estimation of groundwater type and origin of the complex karst catchment using hydrological and hydrogeochemical parameters: A case study of the Gacka river springs

Karst aquifers are heterogeneous terrains, where it is hard to assess any hydraulic parameter. Therefore, a multidisciplinary approach is necessary for research on karst aquifers. Catchment area of the Gacka river springs is typical Dinaric karst terrain built of karstified carbonates. Groundwater flow is mostly directed by preferential flow paths usually connected with main faults and fracture zones. In the presented case study structural geological and tectonic characteristics were defined. A recession diagram was created, and the water balance was calculated. Tracer-test data were also used for analysis. All these data were compared with the bulk hydrogeochemical and isotopic analyses of spring and surface waters. For this purpose, samples were obtained every month for one hydrological year at 17 sampling locations. Processing of all these data allowed a tenable definition of the Gacka spring catchment area.

Implications for karst hydrology from 3D geological modeling using the aquifer base gradient approach

We use the gradient of the aquifer base to investigate the hydrology of mature, shallow karst systems. We first present a 3D geological model of the Gempen plateau (NW Switzerland) that reveals the geometry of aquifers and aquitards and their displacement at faults, then transfer the 3D geological model to a hydrological model. The transformation is based on a conceptual karst model approximating subsurface flow in mature, shallow karst systems to open surface flow on the top of the uppermost aquitard or aquifer base. The gradient of this surface is expected to mainly influence regional groundwater flow patterns. We use the hydrological model to delineate spring catchment areas. The discharge areas and corresponding catchment areas of the model are compared with the occurrence of springs in the study area and with hydraulic links confirmed by tracer tests. We also describe the way in which the hydrological model contributes to identifying flow processes. The proposed aquifer base gradient approach enhances vulnerability assessment in mature, shallow karst regions by (1) localizing catchment areas as a precondition of source protection strategies and (2) indicating dominant flow processes associated with individual springs.

Residence times and age distributions of spring waters at the Semmering catchment area, Eastern Austria, as inferred from tritium, CFCs and stable isotopes

The groundwater system in the mountainous area of Semmering, Austria, was studied by environmental tracers in several karst springs. The tracers used included stable isotopes (18O, 2H), tritium (3H) and chlorofluorocarbons (CFCs). The tracers provided valuable information in regard to (1) the mean altitude of the spring catchment areas; (2) the residence time and age distribution of the spring waters; and (3) the interconnection of the springs to a sinkhole. The combination of the stable isotopic data and the topography/geology provided the estimates of the mean altitudes of the catchment areas. Based on the stable isotopic data the recharge temperature of the spring waters was estimated. The smoothing of precipitation's isotopic signal in spring discharge provided information on the minimum transit time of the spring waters. Due to short observation time, 3H data alone cannot be used for describing the mean residence time of the karst waters. CFCs, though useful in recognizing the co-existence of young (post-1993) water with old (CFC-free) water, could not be used to resolve age distribution models. It is shown in this article, however, that the combined use of tritium and CFCs can provide a better assessment of models to account for different groundwater age distributions. In Appendix A, a simplified method for collecting groundwater samples for the analysis of CFCs is described. The method provides a real facilitation for fieldwork. Test data are given for this sampling method in regard to potential contamination by atmospheric CFCs.

A quantitative real-time PCR assay for the highly sensitive and specific detection of human faecal influence in spring water from a large alpine catchment area

The aim of the study was the development of a sensitive human-specific quantitative real-time PCR assay for microbial faecal source tracking (MST) in alpine spring water. The assay detects human-specific faecal DNA markers (BacH) from 16S rRNA gene sequences from the phylum Bacteroidetes using TaqMan minor groove binder probes. The qualitative and quantitative detection limits of the PCR assay were 6 and 30 marker copies, respectively. Specificity was proved by testing 41 human faeces and waste water samples and excluding cross-amplification from 302 animal faecal samples from Eastern Austria. Marker concentrations in human faecal material were in the range from 6.6 x 10(9) to 9.1 x 10(10) marker equivalents per gram. The method was sensitive enough to detect a few 100 pg of faeces in faecal suspensions. The assay was applied on water samples from an alpine karstic spring catchment area and the results reflected the expected levels of human faecal influence. The method exhibited sufficient sensitivity to allow quantitative source tracking of human faecal impact in the investigated karstic spring water. The developed method constitutes the first quantitative human-specific MST tool sensitive enough for investigations in ground and spring water.

The vulnerability of karst springs—a case study of the Hubelj spring (SW Slovenia)

The hydraulic behaviour of the karst aquifer in the Hubelj spring catchment area (SW Slovenia) was studied by using an indirect research method based on natural tracers. The variations of natural tracers (in precipitation and in groundwater) during the storm event made possible the separation of the Hubelj spring storm hydrograph by the three-component separation technique. The results produced information on the aquifer recharge, storage and discharge processes, as well as on the mechanisms that affected them. They verified the so-called epikarst hypothesis presuming that an important part of a karst aquifer recharge reaches rapidly and intensively from the epikarst zone. It was demonstrated that epikarst water could occupy up to 50% of the spring discharge during precipitation events. This phenomenon could have important consequences on protection and management of the problems of karst aquifers, including engineering problems in karst areas. With this respect the results could give way to new engineering ideas.

Influence of rainfall quantity on the isotopic composition ( 18O and 2H) of water in mountainous areas. Application for groundwater research in the Yunquera-Nieves karst aquifers (S Spain)

The isotopic composition ( 18O and 2H) of rainwater and groundwater was determined in the Yunquera-Nieves hydrogeological unit, a karstic massif in S Spain with complex orography and hydrogeology. The aims were to identify: (1) the source of the water, (2) the main factors determining the isotopic content, (3) the catchment area of the springs and (4) the aquifer behaviour. The isotopic content of the sampled waters is of mixed Atlantic–Mediterranean origin and is opposite to the quantity of rainwater distribution, both in space and time. Spatially, water is isotopically less depleted toward the eastern sector, where rainwater quantity is lower (which is locally affected by the orography): thus, it is possible to differentiate the catchment areas of the main springs. Aquifer recharge is produced by winter precipitation, when rainfall water is isotopically more negative and evaporation is lower. The decrease in rainfall quantity during the study period provoked an increase in δ 18O and δ 2H values, both in rainwater and in groundwater. The recorded variations of the isotopic content of the rainfall are rapidly evident in the spring waters, which demonstrates a well developed karst network inside the carbonate aquifers, and thus the existence of conduit flow systems.

Recharge characteristics of a phreatic aquifer as determined by storage accumulation

The cumulative storage accumulation curve (CSAC) is a tool for saturated-volume fluctuation (SVF) analysis of transient recharge to shallow phreatic aquifers discharging only to springs. The method assumes that little underflow or phreatic evapotranspiration occurs. The CSAC is a modified water-table hydrograph that distinguishes storage increase caused by recharge from loss due to springflow-induced recession. Required for the analysis are water-table fluctuations at a single representative location within the catchment of a single spring and either direct measurements or robust interpolations of springflows at different aquifer stages. The method employs empirical manipulation of head observations, varying spring catchment area to minimize CSAC water-level changes in late portions of long recessions. Results include volumetric estimates of recharge integrated over individual events and instantaneous rates of recharge to the water table, at the temporal resolution of the water-level sampling interval. The analysis may also yield physically realistic information on spring catchment and recharge focusing. In a test case in West Virginia, USA, recharge estimates by this technique were consistent with integrated springflow time series but greater than estimates based on potential evapotranspiration. Results give insight into dynamic recharge behavior over time as well as an indication of recharge catchment size.