Water In Limestone Research Articles

Characterization of Dominant Hydrogeochemical Processes in Groundwater in Onitsha Area, Southeastern Nigeria

The characterization of the dominant hydrogeochemical processes in groundwater in Onitsha area, southeastern Nigeria was carried out. This is to identify the dominant mechanisms responsible for the evolution and the chemical composition of the water sources. A total of fifteen (15) groundwater samples were collected from different locations in the study area in August 2022 and these samples were subjected to chemical analysis using standard methods. The results indicated that the water quality parameters were within the World Health Organization acceptable limits for drinking quality although turbidity in six of the samples exceeded the guideline values. The hydrochemical facies were determined using various plots. Piper diagrams indicated that Ca2+ - Mg2+ - Cl- – SO42- was the dominant facies with Ca2+ and Cl- as the dominant ions. The Durov diagram indicate recharge water in limestone and sandstone aquifers and influenced by important ion exchange reactions. However, the Gibbs plots mainly plotted in the rock dominance zone indicating that the major processes controlling water chemistry in the study area were water-rock interaction and dissolution of rock minerals. The ionic ratio plots were employed to determine the mechanisms and reactions prevalent in the study area that influenced the water chemistry. Na/Cl plot indicated that the excess of Cl- over Na+ was balanced by Ca2+ and Mg2+ while the depletion of Na+ with respect to Clindicated ion exchange reaction which could be attributed to silicate weathering confirming the Na/Cl plot conclusions. The relative abundance of anionic facies shows that Cl- + SO42- were more abundant than HCO3- and the plot of Ca2+ + Mg2+ ions against HCO3- ions depict samples with excess Ca2+ + Mg2+. However, Ca2+ +Mg/HCO3 ratio was less than one (<1) and indicated fresh recharge water.

Influence of Anthropogenic Sulfuric Acid on Different Lithological Carbonate Weathering and the Related Carbon Sink Budget: Examples from Southwest China

Accurate estimate of carbonate weathering and the related carbon sink flux induced by anthropogenic H2SO4 is of great significance for improving understanding of the hydrogeochemical evolution and the global carbon cycle. Here, to quantitatively evaluate the influence of anthropogenic H2SO4 on different lithological carbonate weathering and the related carbon sink budget, karst spring water in the typical limestone and mixed limestone–dolomite catchments in Yaji and Beidiping affected by acid precipitation in southwest China were sampled monthly for the analysis of hydrochemical and δ13CDIC characteristics. Results show for the period of sampling (August 2013 to December 2014) that the average contribution rates of atmospheric inputs and carbonate weathering to total dissolved cations are 2.24% and 97.8%, and 3.09% and 96.9% in Yaji and Beidiping, respectively. The δ13CDIC values (−17.0% to −14.7‰) and the [Ca2+ + Mg2+]/[HCO3−] (0.98 to 1.25) and [Ca2+ + Mg2+]/[HCO3− + SO42−] (approximately 1) equivalent ratios of samples prove that H2CO3 and H2SO4 simultaneously participate in carbonate weathering. The contribution rates of H2SO4 to [Ca2+ + Mg2+] and [HCO3−] produced by carbonate weathering in Yaji and Beidiping are 0–30% and 0–18%, and 0–37% and 0–23%, with average values of 14% and 7%, and 19% and 11%, respectively, suggesting that the influence of H2SO4 on different lithological carbonate weathering is different. H2SO4 precipitation participating in carbonate weathering increases the weathering rate by 14–19%, whereas it decreases the flux of karst carbon sink by 7–11% in Southwest China. Therefore, anthropogenic acids have influenced the global carbon cycle and climate change by carbonate weathering due to the large karst areas in the world, and their influences on different lithological carbonate weathering should not be ignored in the regional and global carbon cycles in future studies.

Effects of Site Karst Water on Fresh Coal Gangue at Baizhuang Coalfield, China—Leaching Characteristic

In mining areas where gangue is used for infill mining, Ordovician limestone karst water is affected by discarded gangue, and the water quality changes significantly. In this study, the effects of gangue on water quality change under different immersion solution conditions were evaluated by Zhai Zhen Coal Mine, Hongqi Coal Mine Ordovician Limestone Karst Water, and Baizhuang Coal Mine. The results showed that the cations in each group of immersion solutions had similar trends, and the Na+ concentration fluctuations were greater in karst water immersion solutions with higher initial sodium ion concentrations, while the fluctuations of calcium and magnesium ions were more obvious in the early stage of immersion, and the fluctuations were gradually slowed down in the later stage. The anions in the immersion solution also have a similar fluctuation trend, but only in the early stage of immersion. By comparing the changes of the three indexes (pH, TDS, and ORP) in the immersion solution, it was found that highly mineralized karst water had a good buffering effect on the changes in the basic water quality index, while the ultrapure water quality index with low salinity had the greatest change. The 100% stacked columnar plot between the main water chemical ion changes shows the relative scale relationship of the water chemical components in the immersion solution at each period, and the water chemical components change significantly in the early immersion period (0–7 d), and then enter the fluctuation changes period, and the ion changes in the fluctuation changes period are mainly Na+ and SO42− ions. This study provides a theoretical basis for exploring the changes of gangue to the quality of karst water in Ordovician limestone and also provides theoretical guidance for the study of groundwater pollution mechanisms in closed coal mines.

Relationships between diatoms and environmental variables in industrial water biotopes of Trzuskawica S.A. (Poland)

Abstract The heterogeneous nature and widespread anthropogenic impacts on industrial water biotopes in the Trzuskawica S.A., pose challenges to biomonitoring of this habitat. Generally, the concentration of trace elements in the industrial water biotopes reflects the anthropogenic impacts. With X-ray fluorescence method (TXRF) in waters 17 elements:P,S,Cl,K,Ca,Ti,Cr, Mn,Fe,Ni,Cu,Zn,Br,Rb, Sr, Ba, Pb were revealed. High amounts of Ca, from 300 ppm to 198 ppm in May and from 999 ppm to 231 ppm in September 2015, was determined. A total of 36 diatoms were found in two reservoirs and drainage ditch, but only three taxa: Cymatopleura radiosa, Navicula upsaliensis and Nitzschia angustata were present in all 7 sampling sites. These species are known to be tolerant to organic pollution, eutrophication, and also characteristic for limestone waters. The results of CVA showed that dintoms in the water reservoir stocked with fish were distinguished by highest species richness. The relationships between diatoms and environmental variables confirm the positive correlation with the currently functioning industrial plant (despite the increased water temperature and large content of trace elements). Our results suggest that, though heterogeneity in both diatoms and selected elements in industrial waters, diatoms can be useful indicators of habitat conditions.

Terrestrial LiDAR Survey and Morphological Analysis to Identify Infiltration Properties in the Tamala Limestone, Western Australia

Caves are an ideal observatory of infiltration water in karstified limestone, and the application of remote sensing techniques can bring new insights toward flow patterns and processes. We present an exhaustive characterization of Golgotha Cave in SW Western Australia, based on a light detection and ranging (LiDAR) measurement campaign. The cave is developed in Quaternary age aeolianite (dune limestone) and its infiltration waters form speleothems. We collect ground-based LiDAR scans of the cave ceiling at three sites within the cave system. The resulting point-clouds are analyzed using mathematical morphology to determine statistical information on stalactite widths, lengths, and spatial distributions. We establish a relationship between stalactite diameter and length that is in agreement with the platonic ideal of stalactite shape. We relate stalactite density variation with topography of the cave ceiling and variations in hydraulic gradient. From this analysis, it appears that longer stalactites tend to occur in comparatively lower ceiling elevation, which, we hypothesize, represents greater mass of water in the limestone above the roof of the cave. We also investigate the relationship between stalactite distribution and ceiling features such as fractures. We apply this to identify different types of possible flow patterns such as matrix flow and fracture flow. This analysis demonstrates a spatial variability, with one site having linear groups of stalactites and another site mostly dominated by stalactite clusters.

Diatoms in the biological assessment of the ecological state of waters using the Czarna Staszowska River as an example

Abstract The object of the present research was the Czarna Staszowska River, which is located in south-eastern Poland and which is a left tributary of the upper Vistula River. The length of the river is 61 km and its sources are situated in the Świętokrzyskie Mountains. The river flows across an area covered by Mesozoic rocks, mostly carbonate and sulfate ones. The upper and middle course of the river is of natural character, while increased pollution occurs downstream of the Chańcza Reservoir. In the present study, the water quality of the Czarna Staszowska is investigated in the pure and polluted sections using diatom indices, such as IO − Diatom Index, IPS − Specific Pollution Sensitivity Index, GDI − Generic Diatom Index and TDI − Trophic Diatom Index. In the four river sections distinguished on the basis of the hydrology and the degree of water pollution, the occurrence of different indicator species was determined in the respective diatom assemblages. Indicator species were determined, i.e. characteristic of oligosaprobic and mesosaprobic, limestone and silicon-rich waters. Also taxa indicating an increased trophic status of the river (occurring in its polluted sections) were identified.

Aquifer storage recovery: an ASR solution to saltwater intrusion at Hilton Head Island, South Carolina, USA

Achieving high recovery efficiency is a goal for almost all aquifer storage recovery (ASR) wells, whether storing fresh water in brackish aquifers or in fresh aquifers containing native water quality constituents that are not wanted in the recovered water. This goal can be achieved rapidly by initial formation and maintenance of a target storage volume (TSV) that includes the water volume required for recovery plus a buffer zone volume that separates the stored water from the surrounding native groundwater. The buffer zone volume is a one-time addition of water to the well. An ASR demonstration project was constructed and tested at Hilton Head Island, South Carolina, USA, storing drinking water in a brackish limestone, semi-confined, artesian aquifer. Operating performance has confirmed the viability of this TSV approach for development of ASR wells. The stored drinking water was recovered at a flow rate of 8 Ml/D for 126 days, with an ending chloride concentration of 170 mg/l, rapidly achieving 100 % recovery efficiency. The storage aquifer had a chloride concentration of 685 mg/l. Results have since been replicated at two other ASR wells on Hilton Head Island, addressing the expected loss of all remaining fresh public water supply wells on the island due to saltwater intrusion. ASR well cycle testing in which the same volume is stored and recovered, with progressively larger storage volumes in each successive cycle, is appropriate for geochemical and microbial studies but is inappropriate for determination of recovery efficiency since any buffer zone is removed during each cycle.

3D mapping of water in oolithic limestone at atmospheric and vacuum saturation using X-ray micro-CT differential imaging

Determining the distribution of fluids in porous sedimentary rocks is of great importance in many geological fields. However, this is not straightforward, especially in the case of complex sedimentary rocks like limestone, where a multidisciplinary approach is often needed to capture its broad, multimodal pore size distribution and complex pore geometries. This paper focuses on the porosity and fluid distribution in two varieties of Massangis limestone, a widely used natural building stone from the southeast part of the Paris basin (France). The Massangis limestone shows locally varying post-depositional alterations, resulting in different types of pore networks and very different water distributions within the limestone. Traditional techniques for characterizing the porosity and pore size distribution are compared with state-of-the-art neutron radiography and X-ray computed microtomography to visualize the distribution of water inside the limestone at different imbibition conditions. X-ray computed microtomography images have the great advantage to non-destructively visualize and analyze the pore space inside of a rock, but are often limited to the larger macropores in the rock due to resolution limitations. In this paper, differential imaging is successfully applied to the X-ray computed microtomography images to obtain sub-resolution information about fluid occupancy and to map the fluid distribution in three dimensions inside the scanned limestone samples. The detailed study of the pore space with differential imaging allows understanding the difference in the water uptake behavior of the limestone, a primary factor that affects the weathering of the rock.

Seepage Field-Strain Field Coupling Analysis for Rock Masses of Coal Seam Floor during Mining Based on COMSOL

Based on the fluid-solid coupling theory, The fractured rock mass was described as a continuous porous medium, and consider the rock mass permeability coefficient has a relationship with the stress and strain. The dynamic change of permeability coefficient was achieved using the multi-physics coupling analysis software COMSOL, and found that the stress and strain of surrounding rocks changes a lot due to mining. The maximum stress and strain in the mudstone area reaches 2-3 times of the original one, which happened at the immediate roof of mined-out area. According to the analysis of seepage field, mining does not destroy water resistance of floor aquifer. Mining fissures do not connect limestone aquifers, and water in the limestone is less likely to flow into stop to cause damage.

Speleothem trace element signatures: A hydrologic geochemical study of modern cave dripwaters and farmed calcite

Trace element variations in ancient cave speleothems are often interpreted as indicators of changes in paleo-rainfall and hydrologic conditions. However, these records are difficult to interpret without an understanding of the physicochemical controls on stalagmite chemistry plus site-specific calibration of changes in net rainfall to variations in dripwater and speleothem chemistry. In this study we examine geochemical relationships between net rainfall (Precipitation minus Evapotranspiration; P−ET), drip rates, drip water chemistry, and contemporaneous calcite chemistry to test the hypothesis that speleothem Mg/Ca and Sr/Ca records are proxies for rainfall amount.HRC is contained within four low-magnesium limestone units capped sporadically by a remnant dolomitic limestone. Aqueous concentrations of magnesium (post evapotranspiration) decrease with increasing vertical travel distance between the soil zone and the point of in-cave drip emergence (Drip Path Length – DPL) as dissolved high-Mg solutions sourced from the dolomitic caprock are diluted with dissolved low-Mg limestone waters sourced from the host limestone. Dripwater Mg/Ca and Sr/Ca ratios covary and provide diagnostic indicators of the two dominant mechanisms controlling dripwater chemistry: (1) mixing of post-evaporative solutions derived from two geochemical endmembers (dissolution of dolomite and limestone); and (2) evolution of hydrochemistry away from dissolved bedrock compositions due to Prior Calcite Precipitation (PCP) above the drip sites. By resolving the linear mixing relationships for drip water Mg/Ca and Sr/Ca sources and the distribution coefficients for trace element transfer in the PCP dripwater-to-calcite precipitation reactions and applying these principles to our time series, we find that the extent of PCP production within the karst is directly controlled by the balance between Precipitation (P) and Evapotranspiration (ET): higher net rainfall (P−ET>1: wet conditions) reduces PCP, and lower net rainfall with increased evapotranspiration (P−ET<1) increases PCP.Farmed calcite X/Ca ratios faithfully track hydrologically-influenced seasonal variations in dripwater chemistry for X=Mg, Sr, and Na. However, the relationship between changes in net rainfall and changes in Mg/Ca and Sr/Ca ratios in modern calcite is unique at each site and differs significantly at closely-spaced drip/stalagmite locations. This suggests that in situ modern hydrochemical calibrations should be performed atop individual speleothems prior to harvesting for paleoclimate investigations, and that such calibrations may not reflect past conditions as drip paths change. We apply this understanding to published dripwater data and speleothem time series from other caves. A major implication is that in order to interpret stalagmite Sr/Ca and Mg/Ca ratios as ‘wet vs. dry’ proxies, speleothem Sr/Ca and Mg/Ca variations must be coherent and in-phase over all time periods (i.e., Sr/Mg ratios must be constant). These criteria will help to distinguish ‘rainfall amount’ versus ‘rainfall source’ in speleothem δ18O records.

Water‐storage capacity controls energy partitioning and water use in karst ecosystems on the Edwards Plateau, Texas

ABSTRACTWoody plants are encroaching into grasslands and savannas of the karst Edwards Plateau, but their impacts on climate and hydrology are unclear because of high variability in soil depth and uncertainties about the contribution of water in fractured limestone to the water available to trees. Water use is controlled by available energy (AE) and its partitioning between latent (λE) and sensible (H) heat fluxes. We hypothesized that the partitioning of AE depends on soil depth, with greater depth leading to more λE and less H. We compared energy fluxes of a deep soil savanna with ~50% woody cover dominated by Ashe juniper (Juniperus ashei) and a shallow soil woodland dominated by live oak (Quercus virginiana) and juniper over a 5‐year period, which included periods of unusually high rainfall and severe drought. Although AE was 7% higher in the woodland, λE was about 2% higher at the savanna over the 5‐year study. Site differences in evapotranspiration were maximal during dry periods between rainfall events, suggesting greater storage of water at the savanna site. During periods of high rainfall, the impact of water storage limitations was minimal, and site differences in evapotranspiration were controlled mainly by AE and its partitioning into H. Both sites were characterized by rapid reductions in λE and reciprocal increases in H during drying cycles following rainfall, indicating that neither of these ecosystems had access to easily utilized sources of deep water. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Application of Pre-Grouting Technique in Yellow River Crossing Tunnel in Eastern Route of South to North Water Transfer Project

The yellow river crossing tunnel runs through limestone at a depth of about 70m below the level of yellow river. Since the river water, phreatic pore water in loose Quaternary deposits and karst/fissure water in limestone communicates with each other, pre-grouting technique has to be employed before drilling and blasting excavation of the tunnel.

Water flow in the Oxfordian and Dogger limestone around the Meuse/Haute-Marne Underground Research Laboratory

Within its scientific program devoted to the feasibility of a high level radioactive waste facility in the Callovo-Oxfordian argillaceous rock (COx) of the eastern Paris Basin, Andra has conducted an extensive characterization of the Oxfordian and Dogger limestone formations above and below the COx. More than 25 wells were dedicated to the hydrogeological and geochemical characterization of the Oxfordian and Dogger limestones over a 400 km 2 sector. An original strategy was developed to obtain field hydrogeological measurements and representative formation water samples in these wells. An extensive 3D set of field data and water compositions were obtained over 15 years. The geochemical and isotopic data indicate a meteoric origin for the Oxfordian and Dogger limestone waters. The geological observations revealed a clay rich level horizontally dividing the Oxfordian limestones into two parts in the NE zone of the study area. In the lower Oxfordian, water inflows come mainly from the outcrop in the south-eastern part of the study area. Three meteoric water inflows were identified in the upper Oxfordian in the study area: the first one covers the eastern and southeastern part of the area, the second one covers the diffuse fracturation zone (DFZ) south of the area, and the third one is located in the north eastern part of the area. The two first inflows consist of fresh water, while the last one consists of Mg 2+, SO 4 2 - and Na + rich waters coming from the erosion of the Purbeckian lithological type facies. Fresh waters from the outcrops flow slowly towards the North West. They equilibrate with the limestone dolomite formations and are enriched by a Na + and Cl − diffusive flux coming from the Dogger through the Callovo-Oxfordian argillaceous rock. These waters mix with the water coming from the North East upper Oxfordian. The Dogger limestone is characterized by sodium chloride groundwaters with higher salinity values than the Oxfordian limestone. North–northwest flows in the Dogger limestone are slower than flows in the Oxfordian formation. In both formations, the DFZ must be considered to be an apart hydrological system.

Numerical analysis of water inrush from working-face floor during mining

Abstract Confined water in the Ordovician limestone is one of the hidden troubles that threaten safe production of mines in north China. A numerical model of the key strata was developed. It included the structural characteristics and mechanical properties of the floor rock at the working face of a particular coal mine. The model was used to predict failure modes and to help establish rules for safe mining above the aquifer. The distribution of deformation, failure and seepage was simulated by using Dilian Mechsoft's Realistic Failure Process Analysis (RFPA2D) program. The stress distribution, the deformation and the flow vectors were also obtained. The results indicate that: 1) The original balance of the stress and seepage fields is disturbed due to coal mining; and 2) As the working face advances different deformation, or failure, appears in the surrounding rocks, the water-resisting strata in floor may be destroyed and the passage of water from the aquifer into the mine may occur. The combined action of mining stress and water pressure ultimately lead to water inrush from the floor.

Water harvesting potential in function of hillslope characteristics: A case study from the Sierra de Gador (Almeria province, south-east Spain)

Surface water in limestone and dolomite mountain ranges in semi-arid regions is very rare. Therefore, water harvesting systems, collecting the runoff from hillslopes, can be found at regular distances to supply water points for grazing animals. The hydrological behaviour of a range of hillslopes and small catchments can thus be studied by monitoring the rainfall and runoff for such water harvesting systems. The number of runoff events collected in four of such systems ranged from 2 to 22 per year during a 7-year period in the Sierra de Gador (Almería province, Spain). The large variation in runoff response can be attributed to the distribution of the rainfall (long-term average 400 mm) and the characteristics of the catchment areas. Rainfall–runoff behaviour was far more erratic than reported for plot studies and rainfall simulations in other semi-arid regions, demonstrating that plot scale results cannot be extrapolated to design water harvesting systems. The aim of this study was to determine thresholds for the production of runoff on hillslopes and zero-order catchments reaching the water harvesting reservoirs at the footslopes. Multiple logistic regressions showed that the rainfall depth per event and the antecedent precipitation index over 20 days (API20) are the main parameters to explain the occurrence of runoff in the reservoirs connected to the four catchments. The hillslopes show a systematic pattern of rock outcrops on the crest and shoulders to a colluvial mantle at the footslopes, where the cisterns are dug out. The rainfall and API threshold of the four catchments, required to produce runoff in the reservoirs, are lowest for hillslopes with a short distance from the rock outcrops to the reservoirs and a low vegetation cover. It was demonstrated that (i) re-infiltration of runoff frequently occurs (56 events not reaching the reservoirs against 14 events with continuous runoff) even within the unlined channel connecting the cistern to the hillslope, and that (ii) the 80% probability of runoff occurrence, calculated using the logistic regression, can be used as a proxy for the total annual runoff to be collected.

Correlating specific conductivity with total hardness in limestone and dolomite karst waters

AbstractUnder field conditions modern digital conductivity meters give standardized, rapid and reproducible measurements. Here we investigate the accuracy of their estimates of the composition of karst waters, as total hardness (TH, as mg/L CaCO3) for limestone and dolomite. These are the fundamental measures of process in carbonate karst geomorphology. PHREEQC theoretical curves for the dissolution of pure calcite/aragonite and dolomite in water at 25 °C are compared with water analyses from karst studies worldwide. Other principal ions encountered are sulphates, nitrates and chlorides (the ‘SNC’ group). From carbonate karsts, 2309 spring, well and stream samples were divided into uncontaminated (SNC &lt; 10%), moderately contaminated (10 &lt; SNC &lt; 20%), and contaminated (SNC &gt; 20%) classes. Where specific conductivity (SpC) is less than 600 µS/cm, a clear statistical distinction can be drawn between waters having little contamination and substantially contaminated waters with SNC &gt; 20%. As sometimes claimed in manufacturers' literature, in ‘clean’ limestone waters TH is close to 1/2SpC, with a standard error of 2–3 mg/L. The slope of the best‐fit line for 1949 samples covering all SNC classes where SpC &lt; 600 µS/cm is 1·86, very close to the 1·88 obtained for clean limestone waters; however, the value of the intercept is ten times higher. The regression line for clean limestone waters where SpC &gt; 600 µS/cm helps to distinguish polluted waters from clean waters with possible endogenic sources of CO2. In the range 250 &lt; SpC &lt; 600 µS/cm, dolomite waters can be readily distinguished from limestone waters. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Determining the Age of What Is Not There

How old is a cave? This is not an easy question. A cave is not an actual object but is rather the absence of material, and ascertaining the age of what is not there is difficult. In his research commentary, Sasowsky discusses results presented in the same issue by [ Polyak et al ][1]. in which a new strategy has been developed for dating caves created by the dissolving action of acidic ground water in limestone. In particular, the method has been applied to two of the most famous caves in the world: Carlsbad and Lechuguilla caves in New Mexico, USA. [1]: http://www.sciencemag.org/cgi/content/short/279/5358/1919

British travertines: a review

A review of British Quaternary travertines is provided, including details of 159 sites presented as a cross-referenced coded list with a full bibliography. Almost all of these travertines were formed by the degassing of calcium bicarbonate waters. The ‘carrier’ CO2 originated from the soil and epigean atmospheres. At most sites, the travertine is composed of calcite as micrite or microspar, but aragonite occurs in the thermal waters of Bath Spa. The chemical composition of 20 samples gave an average CaCO3 content of 94.2% for active sites and 91.6% for inactive sites. Levels of Fe, Mg, Mn, P and Sr are also reported. Stable carbon and oxygen isotope compositions gave values consistent with the degassing of limestone waters in contact with a soil atmosphere. Some evidence indicated that photo-synthetic activity could also influence travertine deposition. Bryophytes and algae in particular, can influence travertine fabrics through the trapping and binding of calcite. The median δ13CPDB was −11.5‰. The British travertines have been classified into seven fairly broad categories: (1) paludal deposits; (2) cascades; (3) barrages; (4) stream/spring crusts; (5) lake crusts; (6) cemented rudites; and (7) clastic deposits. Spring/stream crusts and paludal deposits are the most common types of active and inactive travertines, respectively. Further statistics on deposit size, relation to solid geology and age are presented. Most sites are Holocene in age but the available dates do not point to a specific period of high travertine deposition, even though the Atlantic period (6000–7000 bp) is considered to represent such a time. Only a handful of travertines are known from the Pleistocene.

An approach to estimation of leakage from a karstic limestone reservoir

A prediction of the quantity of water likely to escape through cavernous limestone under full-reservoir conditions may be possible based on the knowledge of void space and average velocity of water in limestone. In practice, in place of actual void space, the total cross-sectional area of limestone in the probable zone of leakage and the “void-ratio” are calculated. A statistical approach with the data obtained from planned exploratory drilling and water percolation tests provides values for void-ratio whereas knowledge of detailed subsurface geology helps to deduce the sectional area. The average velocity of water can be obtained from the study of natural tritium in groundwater or injection of chemical and radioactive tracers and various hydrological investigations, such as water-balance calculations in adjacent basins.

The range of water temperature fluctuations in the limestone waters of the central and southern Pennines

The range of water temperature fluctuations in the limestone waters of the central and southern Pennines