Karst hydrogeology of the Kaş-Kalkan springs along the Mediterranean coast of Turkey

 The present studies were carried out along the southern Mediterranean coast of Turkey, where most of the karst springs discharge from highly karstified carbonate rocks. The case-study was applied in the Kaş-Kalkan karst region, considered one of the most important touristic Mediterranean provinces in southern Turkey. The purpose of this study is to identify the main water resources of the karst springs in the inland side and the expected groundwater flow paths that may recharge the coastal springs in the study area. A comparison of the physiochemical properties and isotopic contents of the karst springs along the Kaş-Kalkan coastline is also considered an important tool for identifying the hydrogeological characteristics and responses of the different units in the study area. Relevant studies were carried out also considering the morphological and structural characteristics of these karst springs and changes in their discharge amounts during the dry and wet periods. Received: 20 August 1997 · Accepted: 2 December 1997     

Comparative discharges of fresh and waste water along the California coast

As the population of California grows, the discharge of domestic and industrial waste water and power-plant cooling water into coastal waters continuously increases. About 0.75 × 10⁶ m³ of industrial waste water, 3.75 × 10⁶ m³ of domestic waste water, and 26.5 × 10⁶ m³ of thermal effluent are discharged daily into California's nearshore waters. These waters do not have an infinite capacity to break down and disperse the pollutants. Waste water discharged near shore may remain there for considerable time and have a significant effect on water quality and marine life. The low population and wet climate of the northern coastal region have led to small discharges of waste water but very large inputs of fresh water to the ocean. Southward along the Pacific Coast the climate becomes more arid, and population increases. This combination leads to a large excess of waste-water over fresh-water discharge. Many individual waste-water discharges exceed the average daily discharge of most of the rivers which enter the coastal waters.     

Hydrogeochemical evolution of groundwater in a Mediterranean coastal aquifer, Mersin-Erdemli basin (Turkey)

In this study, hydrogeologic and hydrochemical information from the Mersin-Erdemli groundwater system were integrated and used to determine the main factors and mechanisms controlling the chemistry of groundwaters in the area and anthropogenic factors presently affecting them. The PHREEQC geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area. In a broad sense, the reactions responsible for the hydrochemical evolution in the area fall into four categories: (1) silicate weathering reactions; (2) dissolution of salts; (3) precipitation of calcite, amorphous silica and kaolinite; (4) ion exchange. As determined by multivariate statistical analysis, anthropogenic factors show seasonality in the area where most contaminated waters related to fertilizer and fungicide applications that occur during early summer season.     

海底地下水排放:重要的海岸带陆海相互作用过程

沿海地区海底地下水排放在北美和欧洲等发达地区受到了越来越多的重视,被认为是一个重要的海岸带陆海相互作用过程。但这一过程在我国尚未引起足够认识,有关研究极少见。海底地下水排放的研究历史不长,只是近十多年才有了快速的发展,有了越来越多的定量研究成果。其研究方法主要有水文计算法、现场实测法和地球化学示踪法,各种方法之间的对比实验是目前的热点问题。沿海地下水排放具有重要的环境意义,它可以是陆地营养物质和污染物质的一个重要排放通道,可以对海岸带环境产生一定影响。我国沿海地区应该加强有关的研究工作,为海岸带环境管理作出贡献。     

人类活动影响下的龙口海岸带海底地下水排泄通量研究

在沿海地区,以²²³Ra和²²⁴Ra为示踪剂建立的镭质量平衡模型已广泛应用于海底地下水排泄量(SGD)的研究中,然而目前国内外关于在人类活动复杂影响较大情况下的SGD研究却极为少见。本文对比研究了在有防渗墙(A区)和填海造陆(B区)两种不同人为因素影响下的龙口海岸带水体表现年龄、海底地下水排泄量及其携带的氮磷营养盐通量。结果表明,A区平均水体表现年龄为14.26 d,B区平均水体表现年龄为10.64 d。此外,B区沿岸地下水以及近岸海水中的Ra活度均普遍高于A区,而盐度低于A区。在SGD方面,A区的SGD速率为1.26~1.60 cm·d^-1,B区为1.43~1.82 cm·d^-1,考虑SGD在评估方法上存在一定的误差,因此两个区域的SGD速率相差不大。但与我国其他自然海域相比,这两个区域的SGD速率均处于较低水平。此外,B区的氮磷营养盐浓度普遍高于A区,而且由SGD驱动的氮磷营养盐通量不同,地下水输入的不平衡的营养盐极易改变龙口海域的营养盐结构,对海洋生态环境产生不利影响,这也进一步证实SGD在沿海生态环境以及水体污染治理中的重要地位。     

Geological characteristics of 2011 Japan tsunami sediments deposited along the coast of southwestern Mexico

The tsunami of 11th March 2011 was originated at the east coast of Japan and deposited ca.1 cm thick sediment layer along the coast of southwestern Mexico up to a maximum distance of 320 m from the beach. The sedimentological, mineralogical and geochemical characteristics of the sediments deposited during the tsunami (JT) are compared with the pre-tsunami sediments (PRT). JT sediments consist of dominant coarser fractions (>54% of medium to coarse sand), whereas PRT deposits comprise abundant finer fractions (>58% of fine sand). Assemblage of mafic and heavy minerals suggests similar provenance for both. The higher abundance and variation of heavy minerals along with higher concentrations of bromine (Br) and sodium (Na) in the JT deposits reveal the influence of high energy sea waves in transportation of heavy mineral rich coarse sediments onto the coastal lowlands.     

Impact of sea level rise and coastal slope on shoreline change along the Indian coast

Densely populated coastal zones of India are highly exposed to natural environment. These are impacted by episodic natural events, continuous coastal process, gradually rising sea levels and coexisting human interventions. The present study is an attempt to assess the implication of the sea level rise and coastal slope in the coastal erosion for entire mainland of India. In this regard, two methods were employed to estimate the shoreline change rate (SCR): (1) satellite-derived SCR using the Landsat TM and ETM+ acquired during 1989–2001 and (2) SCR derived by Bruun Rule using the parameters coastal slope and sea level trend derived from satellite altimetry. Satellite-derived SCR has been compared with the shoreline change estimated based on Bruun Rule, revealing a better agreement with each other in terms of trend. Peaks of shoreline retreat calculated using Bruun model and satellite-observed SCR offset by 25–50 km. Offset in these peaks was observed due to net drift towards north in the east coast and south in the west coast of India, revealing the applicability of the Bruun Rule along the Indian coast. The present study demonstrates that coastal slope is an additional parameter responsible for the movement of shoreline along with sea level change. The results of satellite-derived SCR reveal the highest percentage of erosion along West Bengal coast with 70% followed by Kerala (65%), Gujarat (60%) and Odisha (50%). The coastlines of remaining states recorded less than 50% of coasts under erosion. Results of this study are proving critical inputs for the coastal management.     

Geochemistry and quality of the groundwater from the karstic and coastal aquifer of Geropotamos River Basin at north-central Crete, Greece

In Geropotamos River Basin, located on the north-central part of Crete, Greece, two main factors were believed to be affecting the geochemistry of the groundwater with high salt contents: seawater intrusion and/or Miocene evaporates. To identify the origin of the high salinity in groundwater, a hydrogeochemical and isotopic study was performed. Water samples from 22 wells and 2 springs were analyzed for physico-chemical parameters, major ions analysis, as well as stable isotopes (??¹⁸O, ??D). From the present survey, in which detailed hydrogeochemical investigation was conducted, the uncertainty of the contamination sources was decreased in the northern part of Geropotamos Basin. The results complement the scenario in which seawater and the widespread human activities are the principal sources of groundwater contamination. Moreover, the results of the stable isotopes analyses (??¹⁸O and ??D) support the same hypothesis and make seawater intrusion the most probable cause for the highest salinity waters. It is indicated that saline intrusion is likely to occur along fractures in a fault zone through otherwise low-permeability phyllite?Cquartzite bedrock, which demonstrates the critical role of fracture pathways in salination problems of coastal aquifers.     

Historical shoreline trend analysis and drivers of coastal change along the Ravenna coast,NE Adriatic

One of the most important aspects of coastal zone management is the analysis of shoreline dynamics. Over the last years, beaches of the Ravenna coast (NE Italy) experienced large modifications, in some places narrowing or even being completely lost, thus threatening tourism, coastal assets and nature. Coastal erosion has direct consequences for Ravenna tourist-based economy, which largely depends on the attraction provided by sandy beaches. In this study, long-term (>?50 years) coastal analysis was used to identify the sectors along the coast where the shoreline position has changed, either advancing or retreating. Shoreline changes were measured on GIS environment by means of Digital Shoreline Analysis System (DSAS) extension. Net Shoreline Movement (NSM) and Linear Regression Rate (LRR) strategies were employed to examine shoreline variability and reveal erosional/accretional trends. The results show that significant shoreline changes affected the entire coastal region, with most of the study area under retreat, mainly in the most valuable tourist assets of the littoral. The effects were found to be worsened by impacts of land subsidence, presence of harbor infrastructure and deficit in sediment budget. A simple shoreline classification was performed over the DSAS results and cross-checked with local knowledge of the area. The measurement of erosion or accretion rates in each studied segment is found to be useful for land use planning and coastal management plans, especially regarding the prediction of future shoreline positions. Especially important is the potential of the classification to identify areas of significant position change, with current and future implications for the design of sustainable shoreline management and mitigation measures.     

Assessment of groundwater salinity using GIS and multivariate statistics in a coastal Mediterranean aquifer

The integration of the statistical approaches and GIS tools with the hydrogeological and geological contexts allowed the assessment of the processes that cause groundwater quality deterioration in the great important deltaic aquifer in the northeastern Tunisia (Medjerda Lower Valley Aquifer). The spatial variation of the groundwater parameters and the molar ratio (Cl^?/Br^?) were also used to determine the possible impacts from seawater intrusion and from the septic tank leachate. Sixty shallow groundwater samples were collected in 2014 and analyzed for major and trace ions over an area of about 1090 km² to determine the suitability for drinking or agricultural purposes. The total dissolved solids (TDS) content ranges from 1005 to 19,254 mgl^?1 with a mean value of 3477.18 mgl^?1. The chemistry is dominated by the sodium–chloride waters (55%). Mapping of TDS, Cl^?, Na⁺, SO₄^2? and NO₃^? using kriging method shows a clear increase in salinity toward the coastline accompanied by Na⁺ and Cl^? increase which may be related to seawater intrusion and halite dissolution. Locally, higher nitrate concentration is related to the agricultural activities inducing contribution of chemical fertilizers and irrigation with treated wastewater. The saturation indices indicate that all carbonate minerals tend to reach saturation equilibrium confirming water–rock interactions, while evaporitic minerals are still in sub-saturation state and may increase the salinity of the groundwater. The principal component analysis proves the occurrence of groundwater contamination principally by seawater intrusion in the factor I (74.15%) and secondary by an anthropogenic source in the factor II (10.35%).     

Evolution of groundwater salinity in the unconfined aquifer of Bou-Areg, Northeastern Mediterranean coast, Morocco

The Bou-Areg plain in the Mediterranean coast at the North-eastern of Morocco is characterized by a semi-arid climate. The aquifer consists of two sedimentary formations of Plio-quaternary age: the upper formation of fine silts and the lower one of coarse silts with sand and gravels. The aquifer is underlain by marly bedrock of Miocene age that dips toward the coastal lagoon of Bou-Areg. The hydrodynamic characteristics vary between 10⁻⁴ and 10⁻³ m/s; and transmissivities range between 10⁻⁴ and 10⁻¹ m²/s. The general direction of flow is SW to NE, toward the lagoon. The aquifer is crossed by the river Selouane, which also ends in the lagoon. The groundwater is characterized by a high salinity that can reach 7.5 g/l. The highest values are observed in the upstream and in the downstream sectors of the aquifer. The temporal evolution of the physico-chemical parameters depends on the climatic conditions and piezometric variations. The analysis of the spatio-temporal distribution of the physico-chemical parameters suggests different sources of groundwater salinization: the seawater intrusion, the influence of marly gypsum-bearing terrains, and the influence of anthropogenic products as the agricultural fertilizers, which cause great nitrate concentrations that vary between 80 and 140 mg/l.     

Soft-sediment deformation of Late Pleistocene sediments along the southwestern coast of the Baltic Sea (NE Germany)

A 1,460-m-long profile of a Late Glacial subglacial, glacio-fluvial, glacio-limnic and glacio-deltaic sequence exposed at a cliff section on Usedom Island (SW Baltic Sea coast) is described. The sequence is up to 31 m thick and shows sedimentary structures typical of a glacial setting. Soft-sediment deformation is encountered and is associated with changes in lithology. These deformations include liquefaction, slumping, and faulting. As the most plausible cause, earthquake-induced shaking is discussed. The associated neotectonic activity is seen as a consequence of the postglacial isostatic crustal rebound. As the deglaciation earthquake ratio diminishes with time and as the rebound is phasing out, no large earthquakes are anticipated for northern Germany, although in conclusion the lithosphere of the North German Basin has to be regarded as weakened by repeated ice loading and deloading.     

Monitoring and methods to analyse the groundwater quality degradation risk in coastal karstic aquifers (Apulia,Southern Italy)

A multi-methodological approach based on monitoring and spatio-temporal analysis of groundwater quality changes is proposed. The presented tools are simple, quick and cost-effective to give service to all sorts of users. The chief purpose of the monitoring network is the detection of the piezometric or potenziometric level in the aquifer. The spatial and multi-temporal analysis of usual chemical and physical data provides both an assessment of the spatial vulnerability of the aquifer to seawater intrusion, defining a salinity threshold between fresh groundwater and brackish groundwater and of the water quality trend in terms of salinity. The evaluation of the salinity trend or of salinity-correlated parameters highlights the effects of groundwater mismanagement. The multiparameter logging provides a rapid groundwater quality classification for each well. The whole approach allows evaluating the effects of current management criteria and designing more appropriate management targets. The Apulian karstic coastal aquifers have been selected as a case study (Southern Italy). Three types of aquifer zones can be distinguished: (1) areas with low vulnerability to seawater intrusion, (2) areas with high vulnerability and (3) areas with variable vulnerability in which the salt degradation largely depends on the ability to manage the well discharge. The water quality degradation caused by seawater intrusion appears to be a combined effect of an anomalous succession of drought periods observed from about 1980 onwards and increased groundwater pumping, particularly during drought periods. A management criterion based on aquifer zones is proposed.     

The origin and disappearance of the late Pleistocene-early Holocene short-lived coastal wetlands along the Carmel coast, Israel

The formation of short-lived backswamps along the Carmel coast of Israel coincides with the rapid global sea-level rise during the late Pleistocene-early Holocene transition. The current study shows that the wetland phenomena originated around 10,000 yr ago and dried up shortly before the local Pre-Pottery Neolithic humans settled on the wetland dark clay sediments 9430 cal yr BP. Palaeontological and stable-isotope data were used in this study to elucidate previously published sedimentological reconstruction obtained from a core drilled into the western trough of the Carmel coastal plain. The water body contained typical brackish calcareous fauna, with variable numerical abundance and low species richness of ostracods and foraminifera. The δ¹⁸O and δ¹³C of the ostracod Cyprideis torosa show close similarity to the present Pleistocene coastal aquifer isotopic values. This study therefore concludes that the wetlands were shallow-water bodies fed by groundwater, with no evidence of sea-water mixing. It seems that they developed as the result of high groundwater levels, transportation of sediments landward, and deposition of sand bars at the paleo-river mouths. It is still not fully understood why these wetlands deteriorated abruptly and disappeared within less than 1000 yr.     

Hydrogeochemical assessment of groundwater quality along the coastal aquifers of southern Tamil Nadu,India

Hydrogeochemical investigation of groundwater has been carried out in the coastal aquifers of southern Tamil Nadu, India. Seventy-nine dug well samples were collected and analyzed for various physicochemical parameters. The result of the geochemical analysis indicates the groundwater in the study area is slightly alkaline with moderate saline water. The cation and anion concentrations confirm most of the groundwater samples belong to the order of Na⁺ > Mg²⁺ > Ca²⁺ > K⁺ and Cl^? > SO₄ ^2? > HCO₃ ^?. Thereby three major hydrochemical facies (Ca–Cl, mixed Ca–Mg–Cl and Na–Cl) were identified. Based on the US Salinity diagram, majority of the samples fall under medium to very high salinity with low to high sodium hazard. The cross plot of Ca²⁺ + Mg²⁺ versus chloride shows 61 % of the samples fall under saline water category. Higher EC, TDS and Cl concentrations were observed from Tiruchendur to Koodankulam coastal zone. It indicates that these regions are significantly affected by saltwater contamination due to seawater intrusion, saltpan deposits, and beach placer mining activities.     

Characterization of the groundwater flow system in the hillside and coastal aquifers of the Mersin-Tarsus region (Turkey)

In the region between Mersin and Tarsus cities, located along the Mediterranean Sea coast in southern Turkey, the demand for groundwater has increased dramatically as the available surface water supplies have already been developed. Fundamental information is required to characterize the existing groundwater system in this area in order to establish a sustainable groundwater-use policy. For this purpose, hydrochemical and environmental isotopic data were collected and integrated with available geological and hydrogeological information to develop a conceptual model of the system. Results, backed up mainly by depleted stable isotope composition and infinitesimal tritium content, suggest that most of the groundwater along the coastal zone is supplied by the neighboring mountain belt while local precipitation has also contributes to aquifer recharge. The validation of the conceptual perspective by a steady-state numerical groundwater flow model reveals that about 90% of the recharge to the aquifer system is supplied by the deep flow of karstic groundwater fed from the Taurus Mountains. Monitoring of changes in the recharge regime of the mountain sector seems to be critical in establishing future groundwater use policies.     

Characteristics of groundwater in karstic region in northeastern Vietnam

The groundwater in the karst region of northeastern Vietnam is found in various structural zones such as the Ha Lang, Song Hien, Hon Gai, Song Lo, Song Gam, and Hoang Lien Son Zones, etc. Results from this study show that groundwater in this region is at different depths: ~120 m deep at Quang Ninh, ~100 m at Lang Son, ~80 m at Cao Bang (The most water-abundant depth observed at Cao Bang varies from 40 to 45 m) while it varies from 18–25 to 80 m deep at Quan Ba (Ha Giang), especially at Meo Vac (Ha Giang), where groundwater is observed at 700–800 m deep (equivalent to local base level of the Nho Que River). Overall, groundwater in the region is fresh with total minerals varying from 250 to 400 mg/l; except for the coastal area of Quang Ninh, where groundwater is characterized by much higher total minerals (M = 3–18 g/l) due to the mixing with the saline sea water. The chemistry of water in the region demonstrates that the water is mainly bicarbonate with a [HCO₃ ^?] concentration varying from 150 to 265 mg/l, pH is of 6.5–8.1, and its hardness is of 3.7–6.0 meq/l.     

Submarine groundwater discharge in a subsiding coastal lowland: A Ra and Rn investigation in the Southern Venice lagoon

Several recent studies have suggested that submarine groundwater discharge (SGD) occurs in the Venice lagoon with discharge rates on the same order or larger than the surface runoff, as demonstrated previously in several other coastal zones around the world. Here, the first set of ²²²Rn data, along with new ²²⁶Ra data are reported, in order to investigate the occurrence and magnitude of SGD specifically in the southern basin of the lagoon. The independent connection with the Adriatic Sea (at the Chioggia inlet), in addition to the relative isolation of the water body from the main lagoon, make this area an interesting case study. There is probably only minimal fresh groundwater flux to the lagoon because the surrounding aquifer is subsiding and mainly has a lower hydraulic head than seawater.The data show that the Ra and Rn activities are in slight excess in the lagoon compared to the open sea, with values on the same order as those observed in the northern and central basins. Taking into account the water exchange rate between the lagoon and adjacent seawater provided by previous hydrodynamic numerical modelling, it is shown that this excess cannot be supported at steady state by only riverine input and by diffusive release from the sediment interstitial water. High activities observed in groundwater samples collected from 16 piezometers tapping into the shallow aquifer over the coastal lowland substantiate that the excess radioactivity in the lagoon may indeed be due to the advection of groundwater directly into the lagoon bottom water through the sediment interface. However, the data show that the groundwater composition is extremely heterogeneous, with high Ra activities concentrated within a narrow coastal strip where the contact between fresh and saline water takes place, while Rn strongly decreases when approaching the lagoon shore across the 20 km coastal plain. Assuming that the average groundwater activities measured in the coastal strip are representative of the SGD composition, a SGD flux of 7.7 ± 3.5 × 10⁵ and 2.5 ± 2 × 10⁶ m³/d is calculated using a ²²⁶Ra and ²²²Rn budget, respectively, (i.e. about 1-3 times the surface runoff), substantially lower than in previous studies. The influence of all assumptions on SGD estimates (groundwater heterogeneity, diffusive sediment flux, one-box versus multi-boxes model calculations) is discussed, and a sensitivity analysis of the influence of imperfect exchange and mixing at the lagoon outlets that affects the lagoon composition is provided. Finally, the results confirm that the SGD flux, calculated with these assumptions, is largely (∼80%) composed of saline lagoon water circulating through the sediment under the lagoon margin, and that the fresh water discharge associated with SGD is at most a minor term in the lagoon hydrologic balance.