Modelling groundwater salinisation in irrigated coastal areas

Journal of Hydrology, 2011

Groundwater salinisation is a major groundwater contamination issue worldwide and can be caused by different processes, such as seawater intrusion, agrochemical pollution, geogenic contamination and irrigation-induced salinisation. In many areas, several salinisation processes are superimposed. Since remedial measures vary for different salinisation processes, correct identification is fundamental for adequate design of management strategies: different strategies may be required in one and the same aquifer, depending on which salinisation process is active where in the domain. A simulation-based salinisation risk assessment methodology is proposed, based on the principle of linear superposition of total dissolved solutes in groundwater. In a first step, the measured bulk salinity distribution is used to calibrate a numerical groundwater flow and transport model, accounting for all identified salinisation processes. Then, the bulk salinity distribution is decomposed into different salinity components by adapting the boundary conditions, running a simulation for each salinisation process separately. These simulation results yield the necessary components to calculate the risk index distributions, which are a measure of the respective future potential salinity increase. Overlaying the risk index distributions with a defined threshold concentration reveals risk areas requiring remediation or conservation measures with respect to each process. The risk area maps resulting from this methodology are a promising tool for the design of groundwater management schemes. They condense relevant information from complex dynamic processes obtained from numerical simulations and visualise the results in simple and static maps, accessible to decision makers who are not familiar with groundwater dynamics. The different steps of the salinisation risk assessment procedure are first described and illustrated on a synthetic example and then applied to a real aquifer system in Southern Cyprus (Akrotiri), where three major salinisation processes are superimposed.

Journal of Water Reuse and Desalination, 2013

Climate change and the continuous population growth increase the demand for water, which in arid and semiarid regions, like the Mediterranean, is considered a limited resource. Future demands will not be met by traditional water resources like surface and groundwater. In order to handle increased water demand, the treated wastewater originating from municipal wastewater treatment plants is offered to farmers for agricultural irrigation. Over pumping of fresh groundwater creates seawater intrusion that causes various problems, besides others, to the quality of recycled water used for agricultural purposes. The effects on soils irrigated with saline water are investigated. Actual investigations were carried out in land irrigated with salinity-affected wastewater and non-irrigated land nearby. Soil profile analyses are demonstrated and compared, showing very interesting results and adverse effects on soil resources. Irrigation with saline waters even at slightly above recommended values can have severe effects on soil resources. Various remediation scenarios for preventing seawater intrusion, as well for mitigation or control of soil salinity problems, are also suggested in this study. This case study was carried in the Larnaca district in Cyprus.

DESALINATION AND WATER TREATMENT

This special issue of Desalination and Water Treatment is dedicated to the 2nd International Conference on Water Problems in the Mediterranean Countries (WPMC) which was held 6-10 May 2019 at Near East University in Lefkoşa, Turkish Republic of Northern Cyprus (TRNC) as one of a series organized biennially since 1997. This event, like the previous ones, explored and upgraded the integrated approach towards the protection of water resources in the Mediterranean region by bringing together engineers, scientists, students, managers and other professionals from different countries involved in various aspects of water problems in the Mediterranean region. This integration of water-related problems and water scarcity should be considered as a prerequisite for adopting sustainable solutions to numerous contemporary water problems in the world and particularly in the Mediterranean region. In this issue, 23 papers covering a wide spectrum of scientific contributions on different aspects of the problem were selected and reviewed. The authors and guest editor expect that this issue would provide a valuable overview of recent works done in water-related problems and fulfill scientific gaps indicated previous publications. The guest editor would like to thank all colleagues for their valuable contributions and expresses his appreciation to the Editor-in-Chief, Miriam Balaban, and to the editorial office for providing this opportunity.

International Journal of Environmental Science and Technology, 2018

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 km 2 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 + , SO 4 2− and NO 3 − 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%).

Environmental Earth Sciences, 2006

This paper refers to the development of a conceptual model for the management of a coastal aquifer in northern Greece. The research presents the interpretation and analysis of the quantitative (groundwater level recordings and design of piezometric maps) regime and the formation of the upcone within the area of investigation. Additionally it provides the elaboration of the results of chemical analyses of groundwater samples (physicochemical parameters, major chemical constituents and heavy metals and trace elements) of the area which were taken in three successive irrigation periods (July–August 2003, July–August 2004 and July 2005), in order to identify areas of aquifer vulnerability. The study identifies the areas where ion exchange phenomena occur, as well as the parts of the aquifer where the qualitative degradation of the aquifer system is enhanced. The paper, finally, assesses the lack of any scientific groundwater resources management of the area by the local water authorities, as well as the current practices of the existing pumping conditions scheme as applied by groundwater users.

Environmental Science and Pollution Research, 2014

Coastal aquifers are at threat of salinization in most parts of the world. This study was carried out in coastal shallow aquifers of Aousja-Ghar El Melh and Kalâat el Andalous, northeastern of Tunisia with an objective to identify sources and processes of groundwater salinization. Groundwater samples were collected from 42 shallow dug wells during July and September 2007. Chemical parameters such as Na + , Ca 2+ , Mg 2+ , K + , Cl − , SO 4 2− , HCO 3 − , NO 3 − , Br − , and F − were analyzed. The combination of hydrogeochemical, statistical, and GIS approaches was used to understand and to identify the main sources of salinization and contamination of these shallow coastal aquifers as follows: (i) water-rock interaction, (ii) evapotranspiration, (iii) saltwater is started to intrude before 1972 and it is still intruding continuously, (iv) irrigation return flow, (v) sea aerosol spray, and finally, (vi) agricultural fertilizers. During 2005/2006, the overexploitation of the renewable water resources of aquifers caused saline water intrusion. In 2007, the freshening of a brackish-saline groundwater occurred under natural recharge conditions by Ca-HCO 3 meteoric freshwater. The cationic exchange processes are occurred at fresh-saline interfaces of mixtures along the hydraulic gradient. The sulfate reduction process and the neo-formation of clays minerals characterize the hypersaline coastal Sebkha environments. Evaporation tends to increase the concentrations of solutes in groundwater from the recharge areas to the discharge areas and leads to precipitate carbonate and sulfate minerals.

In this paper the groundwater quality of the southern part of Korinthos region (north-east Peloponnese) is discussed. The geology is characterized by a thick sequence of Neogene marls alternating with sandstones, overlain by superficial Quaternary deposits. The latter consist of a mixture of loose materials such as conglomerates, marly sandstones, sands and clay to silty sands. The area is crossed by a fault system parallel to the coastline, and the Quaternary sediments have formed extended Tyrrhenian marine terraces. Two aquifers have been identified in the area. The first is unconfined and occurs within the Quaternary sediments whereas the other is a deep confined aquifer occurring within the underlying Neogene marl series. Analysis of hydrochemical evolution over the past 30 years has indicated significant deterioration of quality owing to seawater intrusion and nitrate pollution. The various sources of pollution have rendered, to a large extent, shallow groundwater unsuitable not only for potable water supply but also for irrigation purposes. However, this is not the case for the deeper confined aquifer. Statistical analysis was used to explore the evolution of salinization during the years 1968 and 1998. In view of the alarming conditions caused by the documented groundwater quality deterioration, the need for integrated water resources management is stressed to maintain the socio-economic growth of the region studied.

WATER RESOURCES MANAGEMENT, 2014

The coastal aquifer salinization is an urgent problem caused by groundwater resources overexploitation and climate change. This phenomenon is enhanced in areas lying below the sea level, like the polders in the Netherlands or the Po River lowland in Italy. In these reclaimed lands the saltwater intrusion is usually controlled by a network of irrigation canals that supplies freshwater to the shallow aquifer, maintaining soil salinity at acceptable levels. The 2012 was dramatic in terms of agricultural water supply, since the Po River plain experienced a prolonged drought. Despite this, continuous monitoring of piezometric heads and total dissolved solids (TDS) near a canal (Canale della Gronda) demonstrated that freshening was occurring in the shallow portion (first 4 m) of the unconfined aquifer, while the bottom part was characterized by elevated relic salinity. The two-dimensional model SEAWAT was calibrated using piezometric heads and TDS depth profiles measured along a transect perpendicular to the canal. The calibrated model was then used to predict the behaviour of this cross section using a multiple scenario approach: increase in evapotranspiration induced by temperature increase; increase in the frequency of extreme high rainfall events; extreme drought conditions; and canal dewatering due to salinization of the water courses. Moreover, for each scenario, two sub-scenarios were run to account for projected sea level rise. The first three scenarios had only a minor influence on the aquifer salinization rate, while the fourth one predicted serious upward flux of the high salinity groundwater actually residing in the bottom of the unconfined aquifer. The scenarios quantified the possible future effects on groundwater salinization and could be useful to find adaptation strategies to manage the water resources of this and similar areas.

2007

The Thurne catchment in north-east Norfolk, UK, is an extremely important part of the Broads National Park, an internationally important wetland environment. Extensive engineered land drainage of the marshes of this low-lying coastal catchment over the past two centuries has led to land subsidence and the need for drainage pumps to control water levels sufficiently below sea-level to maintain agricultural productivity. Consequently, seawater from the North Sea has intruded into the underlying Pleistocene Crag (sand) aquifer and brackish groundwater enters into land drainage channels, thereby raising their salinity. Powerful pumps discharge these brackish drainage waters into a Special Area of Conservation (SAC) and RAMSAR site, leading to adverse ecological impacts on salt-sensitive species. Chloride concentrations within drainage channels throughout the network have been found to significantly vary, with several influential factors affecting channel salinity such as proximity to th...

Journal of Hydrology, 2006

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