Isotope hydrology of the Aghios Nikolaos area of Crete, Greece

doi:10.1016/0022-1694(88)90209-0

Journal of Hydrology

Volume 98, Issues 1–2, 15 March 1988, Pages 121-132

https://doi.org/10.1016/0022-1694(88)90209-0 Get rights and content

Abstract

Deuterium and oxygen-18 data have been used to identify the origin of recharge to a coastal complex of springs and also aquifers developed for supplying water to Aghios Nikolaos, Crete. Tritium data have been used to estimate the age of groundwater at different sampling locations. The results of this study indicate that the Almyros Aghios Nikolaos springs are recharged mainly from the part of the Gavrovo-Tripolitza limestones forming the mountains of Selena, Katharo Tsivi and Lassithiotika, while the part of the same limestones forming the mountainous area of Mavro Dassos provides recharge to the northern part of the Aghios Nikolaos plateau. The total surfaces of these areas, their corresponding potential annual recharges, as well as the flow velocity of the water recharging the springs of Almyros Aghios Nikolaos during the last few kilometers of its way are estimated.

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Groundwater residence time in basement aquifers of the Ochi-Narkwa Basin in the Central Region of Ghana
2017, Journal of African Earth Sciences
Citation Excerpt :
Environmental Isotopes provide insights into the origin of waters, mixing pattern, flow directions, residence times and climate change scenarios (Das et al., 1988; Leontiadias et al., 1988; Maduabuchi and Faye, 2006; Madioune et al., 2014).
Groundwaters from basement aquifers in the Ochi-Narkwa basin of the Central Region together with rain and surface waters have been analysed for stable isotopes (δ¹⁸O, δ²H and δ¹³C) and radioisotopes (³H and ¹⁴C) to determine sources of recharge, groundwater residence time and flow path. The mechanism of recharge to the groundwaters is by direct infiltration of past local rainfall of mean isotopic composition δ¹⁸O = −3.8‰ V-SMOW and δ²H = −18‰ V-SMOW. Tritium in the groundwaters ranged from 0.05 ± 0.07 to 4.75 ± 0.16 TU. Tritium data revealed that 85% of the groundwater samples were of modern recharge or young waters. The ¹⁴C content of the groundwaters ranged between 9.50 pMC in borehole CR2-50 at Ekumfi Asokwa to 113.56 pMC in borehole CR3-26 at Onyaadze. Evaluation of ³H and ¹⁴C data distinguished three groups of water namely (1) waters characterised by high ³H and high ¹⁴C depicting modern recharge, (2) waters showing a mixture of young and old water due to fractures and (3) waters showing low ³H and low ¹⁴C contents referred to as very old waters and include borehole CR2-50 at Ekumfi Asokwa. The estimated age or residence time of this older water is 19,459 years BP based on uncorrected age. The major flow direction is northwest-southeast. The dominant months contributing to recharge in the study area were February, March, April, May, June, August, September and October. Groundwater residence times in the basement aquifers of the Ochi-Narkwa basin showed that groundwater abstraction is sustainable and requires that the recharge areas are protected from contamination.
Assessment of tritium levels in rivers and precipitation in north-western Greece before the ITER operation
2011, Fusion Engineering and Design
Citation Excerpt :
Only a few isotopic hydrology investigations were conducted recently in Greece [8,27,28]. However, data of tritium measurements in precipitation performed from 1953 to 1984 and tritium measurements in water from boreholes, springs and other water bodies from 1982 to 1987 exist for the Axios River basin, (Central Macedonia, northern Greece) [29], the Aghios Nikolaos area of Crete [30], and Peloponnesus (south Greece) [31]. Because of the lack of data concerning the tritium concentration levels in the environment nowadays, an extended temporal and spatial study was conducted from May 2004 to May 2006.
The project ITER aims to demonstrate that fusion is the energy source of the future. The prototype Tokamak machine is intended to start operation at about 2019 and tritium is one of the major contaminants that can be accidentally released in the environment. Nowadays environmental tritium levels are of natural origin except in the vicinity of nuclear facilities. The evaluation of background tritium levels is essential in the context of a future possibility of accidental tritium releases. For this purpose and also because of the lack of relevant information, an extended programme of river and rain water sampling was implemented in north-western Greece. Water samples from six major rivers in this area and rain water samples were analysed for tritium content. The rivers under investigation were Aliakmonas River, Pinios River, Arachthos River, Kalamas River, Aoos River and Louros River, which originate from the central Greek mountain range Pindos, and flow to Aegean and Ionian Sea.
The tritium concentrations were determined by the Liquid Scintillator Analyser Tri-Carb 3170TR/SL. The statistical analysis of data revealed that there is a seasonal variation of tritium concentration in rain samples and a less pronounced seasonal variation in river samples. The weighted mean tritium concentration for rain samples was determined equal to 0.90 ± 0.08 Bq L⁻¹ (7.6 ± 0.7 TU) and the respective mean value for river samples was 0.94 ± 0.04 Bq L⁻¹ (7.9 ± 0.3 TU). Further analysis has demonstrated that river waters tend to show lower tritium concentrations than the concurrently measured tritium concentrations in rain samples, during spring and summer (at 47% and 71% of the sampling stations, respectively), while this observation is reversed during autumn and winter (at 44% and 35% of the sampling stations, respectively). This may be attributed to rain water remaining underground for a long period allowing tritium to decay and when it reappears as river water, the tritium concentration values are lower when compared to the rain water concentrations. Rough estimates of the residence time of underground waters in the study area provided values, which ranged from 0.5 to 11.7 years, with a mean value of 5.2 ± 0.9 years.
Spatial distribution of the isotopic composition of precipitation and spring water in Greece
2010, Global and Planetary Change
Citation Excerpt :
An extensive literature review has been performed in order to gather all available data on the isotopic composition of water in Greece. Precipitation, spring, borehole, well, river, lake and sea water isotopic, chemical and physical data were compiled from international and Greek sources (Payne et al., 1976; Leontiadis, 1981; Kallergis and Leontiadis, 1983; Leontiadis et al., 1984; Leontiadis and Smyrniotis, 1986; Leontiadis, 1987; Leontiadis et al., 1988; Dotsika and Michelot, 1992; Dotsika, 1992; Leontiadis et al., 1992; Michelot et al., 1993; Christodoulou et al., 1993; Kolios, 1993; Grassi et al., 1996; Leontiadis et al., 1996; Mitropoulos and Kita, 1997; Leontiadis and Nikolaou, 1999; Leontiadis and Stamos, 1999; Leontiadis et al., 1999; Kavouridis et al., 1999; La Ruffa et al., 1999; Kelepertsis et al., 2001; Griffiths et al., 2002; Bencini et al., 2004; IAEA, 2005; IAEA/WMO, 2005; Dotsika et al., 2006a, b; Leontiadis et al., 2006; Stratikopoulos, 2007; Dimitriou and Zacharias, 2007; Duriez et al., 2007; Dotsika et al., 2009). 35 unpublished measurements made by the authors according to the procedures described by Epstein and Mayeda (1953) and Coleman et al. (1982) by means of Finnigan Delta S, and Finnigan Delta V Plus mass spectrometers, are also included.
This paper reviews all available stable isotopic data concerning precipitation and spring water in Greece, from the 1960s until today. Spatial variability is investigated in order to provide basic information and identify the locally significant parameters that affect isotopic distributions. The area of interest was partitioned into eight sections according to geographical location and climatic characteristics. The distance of the station from the sea and the altitude are the main factors imprinted in the isotopic signature of precipitation. Local meteoric water meteoric line (LMWL) for precipitation and spring water were calculated for each section and for Greece as a whole. Precipitation LMWLs differ from the Global Meteoric Water Line (GMWL) in various ways across Greece. Elevated deuterium excess values are observed, probably due to water vapour originating from the Aegean or the Mid-eastern Mediterranean. Spring LMWLs are more or less consistent throughout the country. Furthermore, a high resolution map of precipitation and freshwater spring (Cl⁻ < 200 ppm and T < 25 °C) δ¹⁸O reveals several interesting features such as an orographic shadow effect induced by the Pindos Mountains, a strong climatic signal in southern Greece and a local city-microclimate effect around Athens.
Isotopic composition of precipitation in Greece
2006, Journal of Hydrology
The contribution of stable isotopes in meteorological, climatological and hydrological research is well known. Until this date and despite the fact that several hydrological studies of water sources in Greece have been published, no systematic isotopic study of precipitation has been performed in the country. This paper presents all the available isotopic data collected since 1960 in several Hellenic measurement stations. This data is divided in two periods: the first covers data that was collected in the past, in the frame of a preliminary survey of the isotope composition of precipitation in the Eastern Mediterranean Sea and specific hydrological studies; the second is the result of a three-year coordinated research project of the International Atomic Energy Agency, in which the authors participated, aiming at the systematic study of stable isotopes (²H and ¹⁸O) and ³H in precipitation around the Mediterranean basin. No statistically significant behavior between the two periods of data was found. The isotopic content of precipitation presents characteristics intermediate of those of the Eastern and Western Mediterranean. The tritium concentration in precipitation declines as expected towards the pre-bomb levels, however there is an indication that tritium concentrations are higher in Northern Greece.
δD and δ<sup>18</sup>O evidence for inputs to groundwater at a wetland coastal boundary in the southern Great Lakes region of Canada
1999, Journal of Hydrology
The stable isotope compositions (δ¹⁸O and δD) of water have been used to determine the relative contributions of different water sources to the groundwater in a barrier sand-bar that separates a coastal freshwater marsh from Lake Erie, Canada. An extensive groundwater study was initiated by Environment Canada at Point Pelee National Park after elevated nutrient concentrations were measured in the park’s marsh, located on a spit of land that extends 15 km south into Lake Erie. As part of this larger study, which includes groundwater and nutrient modelling, the stable isotope compositions (δ¹⁸O and δD) of water have been used to independently determine the nature and extent of groundwater flow within sand deposits that separate the marsh from Lake Erie. One of the two study sites chosen for this investigation is located near a large septic-system tile-bed that receives human waste from a public toilet facility within the park, and could potentially release nutrients to the marsh via the groundwater. Both transects studied are well suited to isotopic investigation because they are located between two potentially recharging surface water bodies with temporally variable isotopic compositions, and because the transects are subject to recharge by local precipitation, which exhibits large seasonal isotopic variations. These differing isotopic compositions, when considered spatially and temporally, make it possible to establish the source and movement of groundwater within the transects. The oxygen and hydrogen isotopic compositions of surface waters from the Point Pelee marsh and Lake Erie lie on an evaporation line with a slope of 5.7. The isotopic composition of Lake Erie remained relatively stable for over 21 months (δ¹⁸O=−7.5‰ to −6.7‰) whereas the marsh exhibited considerable spatial and temporal variability (δ¹⁸O=−8.4‰ to −0.1‰). The δD and δ¹⁸O values of precipitation samples vary seasonally with local surface temperatures, and constitute a local meteoric water line of δD=8.0(δ¹⁸O)+9.8. While influx of precipitation is evident and similar in the upper two metres of both transects, the relative contribution to groundwater from Lake Erie and the Point Pelee marsh appears to differ. The average δ¹⁸O and δD groundwater values measured for the narrower transect were −7.0‰ and −54‰ respectively, and reflect significant groundwater recharge from both Lake Erie (∼67%) and the marsh (∼28%). Precipitation constitutes the primary source of groundwater recharge to the wider transect, located near the large septic-system tile-bed, with average groundwater values of δ¹⁸O=−9.1‰ and δD=−65‰. The isotopic profile of groundwater in this area is very stable, both with depth and over time, and contrasts sharply with the narrower northern transect which is much more dynamic. These findings suggest that the septic-system tile-bed is well situated in the wider portion of the barrier sand-bar, where a larger head difference between the lake and the marsh would be required to produce groundwater flow equivalent to that observed in the narrower transect. The differences in groundwater recharge between the two sites arise primarily from the difference in width, and account for the 2‰ and 10‰ differences in δ¹⁸O and δD values, respectively, measured in the base-flow groundwater of the two transects.
Isotope hydrology study of areas in Eastern Macedonia and Thrace, Northern Greece
1996, Journal of Hydrology
Sampling of springs, for which the mean elevation of recharge could be estimated, provided an estimate of −0.44‰ 100 m⁻¹ for the groundwater altitude effect on the δ¹⁸O value in Eastern Macedonia and −0.21‰ in Thrace. A slight difference in both the slope and the intercept of the lines expressing the regression of elevation against δ¹⁸O values in the continental part of Thrace and the island of Thassos, is also observed.
As case studies, the isotopic composition of surface water and groundwater was used to investigate the mechanism of recharge of groundwater in the areas of Lekani Mountains and Thassos Island. As a result, the contribution of water leaking from the river Nestos to the recharge of the springs of Paradissos, near to the river bed, Kastro Filippon and Aghios Athanassios, at a distance of over 25 km from the river bed, as well as of the aquifers tapped by boreholes in the plain between Kastro Filippon and Aghios Athanassios, was indicated. The estimate is 54 ± 12% for the contribution of the river water to the spring yield, in the case of Aghios Athanassios, and 43 ± 10% in the case of the springs of Paradissos.
As another result, the hydraulic connection between the marbles of Profitis Ilias and the marbles and dolomites of Potamia series, in the case of Thassos Island, was confirmed.
Finally, the extent of the carbonate rocks and the amount of precipitation effective in recharge to the main springs, as well as to the aquifers tapped by boreholes in the different plains of the areas under investigation were estimated.

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Research paperIsotope hydrology of the Aghios Nikolaos area of Crete, Greece

Abstract

J. Hydrol.

Nuclear techniques in groundwater hydrology

Statistical Treatment of Environmental Isotope Data in Precipitation

Guidebook on Nuclear Techniques in Hydrology

Water balance investigation in the karstic region of Hungary

Research paper
Isotope hydrology of the Aghios Nikolaos area of Crete, Greece