Water supply potential and optimal exploitation capacity of karst aquifer systems

The management of groundwater flow systems in karst regions appears, at present, to be the most important procedure for solving water deficiency problems during periods of low rainfall. Faced with a lack of data for characterizing the water supply potential of karst aquifers, analyses of spring hydrographs may provide valuable indirect information regarding the structure of karst hydrogeological systems. To estimate the optimal exploitation capacities of karstic sources, a stochastic-conceptual approach was applied in case studies from the Serbian karst. Water supply potentials were initially evaluated on the basis of groundwater budgets. Further steps towards defining optimal “exploitable” regimes included analyses of storage changes in karst water reservoirs under natural conditions and calculation of the potential expansion of currently tapped sources. The results obtained through these analyses are a significant contribution to feasibility studies and aid in the avoidance of problems of overexploitation.     

Hydrogeological characteristics of some deep siphonal springs in Serbia and Montenegro karst

In terms of hydrogeological, engineering-geological, and hydrotechnical tapping in karst in relation to ground waters, karst channels, springs and ponors, speleodiving is the only research method which enables direct observation, studying and exact geological mapping of karst channels and caverns. Data collected during speleodiving research contribute considerably to the analysis of karst evolution process in the given region, which is very important in evaluating the depth of karstification and determining the main direction of the groundwater flow. In the past 30 years in Serbia and Montenegro, speleodivers have investigated over 40 siphonal springs, active cave channels and ponors, of which more than 20 are proof of deep siphonal circulation in karstic aquifers. The karstic springs are the most interesting phenomenon from a hydrogeological view point, and their investigations need particular attention. Most of significant karstic springs are on the rims of erosion basins—perimeters of karst poljes, river valleys, sea coasts and contact areas between karst aquifers and hydrogeological barriers. General characteristics of the spring regime are the direct correlation between precipitation and spring discharge. Moreover, the hydrogeological regime of these springs also depends on the size of the catchment area, karstic aquifer retardation capacity, total porosity, as well as lithological and structural characteristics.     

Management of karst water resources in mining area: dewatering in mines and demand for water supply in the Dongshan Mine of Taiyuan, Shanxi Province, North China

Coalfields in North China contain six to seven coal seams in the Permo-Carboniferous strata. The coal seams are underlain by the Ordovician limestone. Large-scale dewatering or depressurizing of the karst aquifer was considered essential to avoid water inrushes and keep the mines safely operational. This practice, however, has caused water supply shortage in the mining areas. The most effective solution to this conflict is to use the uncontaminated karst water from the mines for water supply. This paper explores a management model to maximize the utilization of the karst water while maintaining the safe operation of the mines. The model can provide essential information on water resource distribution for decision makers. The model was applied to the Dongshan Coal Mine in Taiyuan City, China.     

Dinarides东南部跨界岩溶含水层的特性

Dinarides南部是世界上岩溶发育最强烈的地区之一,同时也是欧洲降水量最大的地区。区内碳酸盐岩沉积厚度大于300m,平均岩溶发育深度从250m 至350m,沿断裂发育的岩溶,甚至更深。地下水平均流速变化较大,从0.002 cm/s至55.2cm/s。地下水滞留时间很短,水位变化非常迅速,变幅高达312m。地下水位对强降雨的响应小于4小时。岩溶大泉的主要特征是管道出口深,最大最小流量变化大。区内发育的落水洞有成千上百个,其中一些落水洞排水能力超过100m3/s,规模巨大并被洪水暂时淹没的岩溶坡立谷闻名世界各地。泉水天然流量和野生动物生存环境的改变,特别是当地特有物种的破坏,已经成为新近许多岩溶工程项目的焦点议题。由于该区极其复杂的水文地理和政治环境,不同国度间的跨界含水层似乎是一个非常敏感的问题。     

Monitoring of percolation water to discriminate surficial inputs in a karst aquifer

 A long-term study on the chemistry of percolating waters in a very large touristic karst cave (Grotta Gigante, northern Italy) was carried out in order to define recharge zones, flowpaths, and possible anthropogenic contamination from the neighboring area. On the basis of a multivaried analysis of the chemical parameters, a discrimination of the dripping points was attempted. Percolation waters whose recharge zone is in the northernmost sector of the cave appeared permanently affected by the anthropic settlements and agricultural activity on the ground surface. Received: 28 April 1997 · Accepted: 3 February 1998     

Characterising the main karst aquifers of the Alvand basin, northwest of Zagros, Iran, by a hydrogeochemical approach

The Alvand River basin, situated in the northwest of the Zagros mountain range, Iran, drains carbonate aquifers through some important karst springs. The physical, chemical and isotopic characteristics of spring water were studied for two years in order to assess the origin of groundwater and determine the factors driving the geochemical composition. Principal components analysis was used to identify the main factors controlling the water chemistry. Two groups of springs were identified: (1) low mineralisation, ion concentration, especially sulphate, low temperature, light isotope composition and high elevation of the recharge area, and (2) moderate to high mineralisation, especially sulphate, higher temperature, heavy isotope composition and low altitude of the recharge area. The main factors controlling the groundwater composition and its seasonal variations are the geology, because of the presence of evaporite formations, the elevation and the rate of karst development. In both groups, the carbonate chemistry is diagnostic of the effect of karst development. The supersaturation with respect to calcite indicates CO₂ degassing, occurring either inside the aquifer in open conduits, or at the outlet in reservoirs. The undersaturation with respect to calcite shows the existence of fast flow and short residence-time conditions inside the aquifer. A PCA analysis showed that, contrary to most developed karst systems, where dilution occurs during the wet season, leaching of the gypsum-bearing Gachsaran Formation by rainwater produced higher mineralisation.

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Resumen La cuenca del río Alvand, situada en el noreste de la cadena montañosa Zagros drena acuíferos compuestos por carbonatos a través de manantiales kársticos. Durante dos años se estudiaron las características físicas, químicas e isotópicas del agua de manantial con el objetivo de determinar el origen del agua subterránea y de los factores que controlan su composición geoquímica. Se utililizó el análisis de componentes principales para identificar los factores principales que controlan la química del agua. Se identificaron dos grupos de mantaniales: (1) de baja mineralización, concentración de iones especialmente sulfatos, y baja temperatura, composición de isotopos livianos y elevación alta del área de recarga, y (2) mineralización moderada y alta, especialmente, sulfatos, y temperatura más alta, composición de isotopos pesados y altitud más baja del agua de recarga. Los factores principales que controlan la composición del agua subterránea y sus variaciones estacionales son la geología debido a la presencia de formaciones evaporitas, la elevación y la tasa a la que se desarrolla el karst. En ambos grupos la química de los carbonatos es un diagnóstico del efecto del desarollo de la estructura kárstica. La supersaturación con respecto a la calcita indica presencia de CO₂ que está en proceso de degasificación que ocurre dentro de acuífero en conductos abiertos o a la salida en reservorios. La subsaturación en lo referente a la calcita muestra la existencia de flujo rápido y de tiempos cortos de residencia al interior del acuífero. El análisis de componentes principales muestra que a diferencia de la mayor parte de sistemas kársticos en donde la dilución ocurre durante la temporada de lluvias, la lixiviación de la formación Gachsaran que contiene yeso a causa de lluvia produce mineralizaciones más altas.

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Résumé Le bassin de la rivière Alvand, situé dans le nord-ouest de la chaîne de montagne Zagros, draine des aquifères carbonatés par le biais dun important réseau de sources karstiques. Les caractéristiques physiques, chimiques et isotopiques de leau provenant des sources ont été étudiées pendant deux ans afin de déterminer lorigine de leau souterraine et les facteurs responsables de sa composition chimique actuelle. Lanalyse des éléments chimiques majeurs a été utilisée pour identifier les processus qui contrôlent la composition chimique de leau. Deux groupes différents de sources ont été identifiés: (1) faible minéralisation et concentration en ions, spécialement en sulfates, faible température, composition isotopique légère et haute élévation de la zone de recharge, et (2) minéralisation moyenne à élevée, particulièrement en sulfates, température élevée, composition isotopique lourde et plus basse altitude de la zone de recharge. Les facteurs principaux qui contrôlent la composition et la variation saisonnière de leau souterraine sont la géologie, en raison de la présence dévaporites, lélévation et le taux de développement des karsts. Dans les deux groupes, la teneur en carbonates est un diagnostic de leffet du développement de la structure des karsts. La sursaturation par rapport à la calcite indique un dégazage en CO₂ qui a lieu soit à lintérieur de laquifère, dans les conduits ouverts, ou à sa sortie, dans les réservoirs. La sous-saturation par rapport à la calcite indique lexistence dun écoulement rapide et un faible temps de résidence dans laquifère. Une analyse des éléments chimiques majeurs a démontré que contrairement aux systèmes de karst les mieux développés où la dilution a lieu lors de la saison humide, le lessivage du gypse de la formation de Gachsaran par leau de pluie produit une minéralisation plus élevée.

     

Temporal variability of phosphorus fractions in Irish karst springs

Transfer pathways of phosphorus (P) from soil to surface waters are the subject of much current research because of concerns about eutrophication. However, P transfer via groundwater discharge has received little attention. Temporal P changes at eight Carboniferous limestone karst springs from two catchments in western Ireland are examined. The eight springs were sampled fortnightly between June and October 1999 and thereafter monthly until February 2000. Each sample was analysed for total P (TP), total dissolved P (TDP) and dissolved reactive P (DRP). Total P exhibited some hydrological response at all springs (e.g. increase from 45 to 107 µg l^–1) reflecting significant changes in particulate P (PP) (e.g. increase from 7 to 44 µg l^–1) and dissolved organic P (DOP) (e.g. increase from 0 to 27 µg l^–1), with DRP displaying greatest temporal stability. Greatest response to rainfall events occurred after the first major autumnal rains in September 1999, when there appeared to be dislodging of loosely bound PP and DOP, which was transported to groundwater. This response to the first autumnal rains probably reflects the hydrological switch where the catchments change from a soil moisture deficit to a soil moisture surplus situation. Daily autosampling demonstrated TP concentrations of up to 1,814 µg l^–1 due to local pollution, highlighting the need to adopt storm event driven sampling rather than discrete sampling in karstic springs. Identification and management of springs in karst areas, with associated point recharge via swallow holes, presents an urgent and demanding challenge.     

Groundwater monitoring for cement kiln dust disposal units in karst aquifers

Well-developed karst aquifers tend to be heterogeneous and consist of variable porosities. Groundwater monitoring and the associated data interpretations in such aquifers are often more complicated than porous medium aquifers. Collection of representative data in karst aquifers often requires monitoring at appropriately located wells and/or springs that are proven to connect to the groundwater system. Water samples are to be collected under different flow conditions, including base flow, high-flow, and low-flow. The sampling frequencies may vary from several months for base flows to minutes in response to recharge events. The groundwater monitoring program presented in this paper is for a cement kiln dust mono-fill site in a karst area of southern Indiana. Following dye tracing and extensive geophysical investigations, one spring was selected as a monitoring location. A second spring should be used as a monitoring location when the last cell of the mono-fill begins receiving the wastes. The paper discusses results from the first spring, at which nine background sampling events were completed to evaluate the natural variations of the water quality. Based on the background data, a statistical evaluation plan was developed for 12 water-quality parameters to determine the integrity of the landfill. The statistical power of the statistical analyses was evaluated by Monte Carlo simulations.     

Specific yield of phreatic variation zone in karst aquifer with the method of water level analysis

Regime of groundwater level is a comprehensive reflection of the hydrogeological environment from the perspective of groundwater. Based on the analysis of the water-level change of 65 groundwater monitoring points from 1987 to 1990, it is found that intermittent cones of depression came into being due to groundwater exploitation in Guilin during the observation period. The buried depth of groundwater in the drawdown cones, the annual variation of water level and specific yield have higher values. Improvement has been made to the formula of infiltration coefficient of precipitation. By using the precipitation response data recorded at every 15 minutes for water level of No. 9 borehole which is near Zengpiyan Cave, the specific yield of phreatic variation zone is indirectly calculated by using the modified formula. The results are range from 0.012 to 0.462 and the spatial distribution of specific yield is ascertained. These make up the deficiency that empirical values cannot be categorized based on the actual conditions. What’s more, the widely used Aviriyanover’s empirical formula is poorly applicable to karst area. This is due to its strict requirement for outside conditions, such as shallow buried depth, homogeneous aquifer medium and small hydraulic gradient.     

Spring and conduit sediments as storage reservoirs for heavy metals in karst aquifers

Sediment samples were collected from six springs draining the karst aquifer at Fort Campbell, Kentucky/Tennessee. These were analyzed by ICP-MS following an extraction procedure that separates the metals into exchangeable, carbonate, oxide, organic and residual fractions. Aluminum and iron are primarily present in the residual fraction while manganese may be dominantly in either the oxide or carbonate fraction. The redox-sensitive metals (Fe and Mn) have the greatest fractional distribution in the spring with the thickest sediments. Trace metals detected include Cr, Cd, Ni, Pb, and Zn in the range of a few to 200 mg/kg. In Beaver Spring, nickel is distributed between the exchangeable, carbonate and organic fractions, while in Gordon Spring, nickel is largely residual. Chromium is almost entirely associated with the organic fraction in Beaver Spring while it is largely residual in Gordon Spring.     

Impacts of karst paleo-sinkholes on mining and environment in northern China

The karst paleo-sinkhole is a special geological structure widely found in the coal measures of northern China. Some paleo-sinkholes have high permeability and connectivity, making them excellent connectors between the karst aquifer and the coal seam. Consequently, during coal extraction disastrous water inrushes take place frequently, which cause severe loss not only in mine submersions and personnel casualties, but also in environmental quality. Locations and the geological and hydrogeological characteristics of paleo-sinkholes in northern China are presented. In-situ drilling and excavation results show that paleo-sinkholes have different hydrogeological behaviors in different regions and in different mines. Based on observed data, mining-induced strata failure in the seam floor is analyzed. The existence of paleo-sinkholes increases the floor strata failure zone. Numerical simulation then is adopted to model coal mining with the effects of both the paleo-sinkholes and the water pressure in the confined aquifer. Analyses of the simulation conclude that the paleo-sinkhole induces the increase in the strata failure and deformation. These make water inrushes more likely to happen.     

Groundwater potentiality index: a strategically conceived tool for water research in fractured aquifers

Durable development requires full profit and knowledge of natural resources potentialities. Multi-criterion approaches that encompass geological, morphological, hydrological and Geographical Information System technologies are ones of exiting developments in environmental sciences. This work is a proposition of a numerical model based on a groundwater potentiality index (GPI) calculation, using data on rock fracturing, lithology, drainage, topography, rainfall and drilling water yield. It provides the ability to identify areas indicating favorable conditions for exploratory well positioning in semi-arid zones with non-permeable outcrops. It is therefore a helpful tool to assist water resources prospecting in deprived regions. The newly conceived approach has been applied in the southeastern boundary of the Bouregreg and coastal basins of Central Morocco, where Paleozoic fractured rocks outcrop. The suitability of the GPI method use was verified by comparing the GPI map values with water yield of thirteen pumping tests in a field checking area, which revealed promising results.     

Impact of karst water on coal mining in North China

Coalfields in North China encompass more than ten Provinces. They contain six to seven coal seams in the Permo-Carboniferous strata. The lower three seams account for 37% of the total reserves and are threatened with intrusion of karst water from the underlying Ordovician limestone. Hundreds of water inrush incidences have occurred, in which a large amount of water suddenly flows into tunnels or working faces under high potentiometric pressure. Over 50 mines have been flooded over the last 30 years. Large-scale dewatering or depressurizing of the karst aquifer was considered essential to avoid water inrushes and keep the mines safely operational. This practice, however, has caused sinkholes, dry springs, water supply shortage, and groundwater contamination in the surrounding areas. One alternative water control measure is to make full use of the rock layer between the coal seam and the karst aquifer as a protective barrier to prevent or constrain water flow from the underlying aquifer into the mines. Grouting is effective when the hydrogeological conditions are favorable to this technique. Proper design of the grouting program and experience of the contractor are also important for a successful application.     

Protection of karst aquifers in the Dinarides in Croatia

 This paper presents karst water protection measures being introduced in the Dinarides of Croatia. The spring sites for the water supply of the town of Rijeka, for its 200 000 inhabitants and the largest harbor of the northeastern side of the Adriatic Sea, have been used as a pilot research area. The European research project was used, and protection of water was generally divided into three phases. A categorization of springs has been made, and five basic protection zones have been distinguished. The rules of behavior in protected zones have been outlined. For the first time, the term water-supply "reserve" has been introduced, referring to the parts of the mountainous region where karst groundwater is recharged. Received: 26 March 1997 · Accepted: 22 July 1997     

Affordable water resource development in the northern province, South Africa

An approach to groundwater exploration and utilisation is presented in an area that was traditionally regarded as having scarce groundwater resources. The area is situated in the Northern Province of South Africa and is known as the Nebo Plateau, which is formed by the Nebo Granite of the Lebowa Granite Suite, Bushveld Igneous Complex. Several historic tectonic events resulted in previously unutilised aquifers, of which the Spitskop Complex and geological lineaments associated with the Wonderkop Fault are examples. Both these areas show promising results, although high fluoride content in the groundwater may pose a problem. This can, however, be solved by treatment processes. The paper emphasises that the influence of the regional geology must be taken into account when exploring and developing groundwater in areas underlain by hard crystalline rocks.     

Hydrogeological conditions for the forming and quality of mineral waters in Serbia

In the past researches conducted on the territory of Serbia, 5 regional geotectonic units have been distinguished with registered occurrences of 230 mineral springs. Recent analyses of the bottled mineral waters quality have not included systematic examinations of micro-components present in these waters. Based on the analyses of the bottled mineral waters (EuroGeoSurveys Geochemistry Expert Group), it has been observed that the water quality is greatly influenced by the chemical composition of igneous intrusions, regardless of the fact that the analyzed waters have been taken from different aquifers (Neogene sediments, limestone, flysch, schist).     

Flow and solute transport monitoring in the karst aquifer in SW Slovenia

The role of the unsaturated zone in the karst aquifer hydraulic behaviour was brought into focus in these studies of the catchment of the Hubelj spring (SW Slovenia). The variations of natural tracers in precipitation and in groundwater during a summer storm event made it possible to trace local flow and solute transport in the observed aquifer. The results produced data on the aquifer recharge, storage and discharge processes, as well as on mechanisms that affected them, which reflects a karst groundwater dynamics also at a regional scale. They point out the significance of effects of the fast preferential flow—epiflow that is the main factor controlling solute/contaminant transport towards the aquifer saturated zone. Numerous arguments indicate that the karst aquifer flow and solute transport mechanisms depend on the hydraulic behaviour of the epikarst zone.     

A transdisciplinary analysis of water problems in the mountainous karst areas of Morocco

Water management and engineering in the karstic High Atlas of Morocco are difficult tasks under the prevailing geological, hydrogeological, geomorphological, vegetational and climatic conditions. It is important to be able to understand and predict the characteristics and availability of water for future water planning in the region under changing climatic and agricultural conditions. An interdisciplinary analysis of problems and adequate hydrological modelling tools developed by geologists, hydrologists and biologists are necessary. The karst areas of the High Atlas Mountains are characterised by impermeable triassic basalt underlying substantial subsurface reservoirs with high potential discharge rates. The karst groundwater aquifers are extensive but largely unknown in dimension, probably with a hierarchical network of groundwater flow paths. It is estimated that approximately 70% of the surface water is directly lost to groundwater. Steep landslide- and debris flow prone slopes exist next to coarse-grained, highly porous river beds. Infrequent, high intensity rainfall or snowmelt causes a particularly high flood risk to these karst areas. In addition, agriculture and land use changes have degraded the karst areas. The most important driving forces for degradation include permanent overgrazing even during droughts and the use of firewood by a continually growing population. Large scale degradation of vegetation has occurred in the oro-mediterranean (mountainous Mediterranean) zone, between 2600 and 3400 m which coincides with the most important zone for karstic groundwater creation. The combination of high amounts of groundwater flow and rapid surface flow due to sparse vegetation has increased the problems of flood flow.     

Hydrogeologic investigations of contaminant movement in karst aquifers in the vicinity of a train derailment near Lewisburg,Tennessee

A train derailment near Lewisburg, Tennessee, in October 1990 prompted two series of groundwater investigations. The first was to determine the subsurface flow route of chloroform and styrene that sank into the underlying karst aquifer. The second was to determine the source of contamination for two nearby residential wells which were found to be contaminated with trichloroethylene (TCE). Water-sample analysis and a dye trace performed at the time of the train derailment indicated groundwater flow to Wilson Spring. A dam was constructed to contain the entire discharge from the spring so that it could be treated before being discharged into Big Rock Creek. Three springs and three water wells were contaminated with chloroform and styrene. Dye traces were performed to determine groundwater flow directions in the vicinities of the TCE-contaminated wells and in the vicinities of potential sources. At the train derailment, the chloroform and styrene sank into the Upper Ridley Karst Aquifer and pooled on top of the Lower Ridley Confining Layer. An exploratory well revealed a layer of chloroform (a Dense Non-Aqueous Phase Liquid DNAPL) on the bottom, a layer of groundwater in the middle, and a layer of styrene (a Light Non-Aqueous Phase Liquid LNAPL) on top. Groundwater with relatively low levels of chloroform and styrene in solution was carried by a small cave stream southeast along the strike to Wilson Spring. Chloroform product moved by gravity southwest down-dip along weathered bedding planes. Treatment of contaminated groundwater from Wilson Spring and recovery wells at the spill site has occurred continuously since October, 1990.     

Simulation of the development of karst aquifers: role of the epikarst

 The evolution of a karst aquifer is modelled taking into account the karst groundwater flow as well as the dissolution kinetics of calcite. In particular, infiltration of water from the epikarst is simulated which controls the temporal and spatial distribution of recharge to the phreatic zone. The results show that the evolution of karst conduits is initiated in the spring. The existence of preferential flow paths leads to the evolution of highly conductive so-called dendritic cave systems, i.e., single passages which concentrate the flow and drain the catchment. With time, the amount of undersaturated water flowing directly into the conduit system is increased leading to an acceleration of the conduits enlargement. Three phases are identified for the evolution of karst aquifers: (a) an initiation stage; (b) an enlargement stage; and (c) a stagnation phase. Received: 4 August 1997 / Accepted: 19 January 1998