Elsevier

Journal of Hydrology

Volume 561, June 2018, Pages 236-249
Journal of Hydrology

Research papers
Surface–ground water interactions and hydrogeochemical evolution in a fluvio-deltaic setting: The case study of the Pinios River delta

https://doi.org/10.1016/j.jhydrol.2018.03.067Get rights and content

Highlights

  • Surface-ground water interactions modify water quality in space and time.

  • Mineral dissolution and cation exchange processes control water quality.

  • Nitrates in groundwater are due to agricultural and domestic effluents.

  • NO3 values in the river are relatively low compared to European systems.

  • The river water quality is characterized by high quality WQI rankings.

Abstract

River deltas sustain important ecosystems with rich biodiversity and large biomass, as well as human populations via the availability of water and food sources. Anthropogenic activities, such as urbanization, tourism and agriculture, may pose threats to river deltas. The knowledge of the factors controlling the regional water quality regime in these areas is important for planning sustainable use and management of the water resources. Here, hydrochemical methods and multivariate statistical techniques were combined to investigate the shallow aquifer of the Pinios River (Thessaly) deltaic plain with respect to water quality, hydrogeochemical evolution and interactions between groundwater and surface water bodies.

Water quality assessment indicated that most of the river and groundwater samples fully comply with the criteria set by the Drinking Water Directive (98/83/EC). The river is recharged mainly from springs of the Tempi valley and the shallow aquifer, and to a lesser degree from precipitation, throughout the year. The hydrogeochemical characteristics indicated a cation (Ca, Mg, and Na) bicarbonate water type, which evolves to calcium-chloride, sodium-bicarbonate and sodium-chloride water type, in the northern part of the delta. Calcite and dolomite dissolution determined the major ion chemistry, but other processes, such as silicate weathering and cation exchange reactions, also contributed. In the northern part of the plain, the interaction with the deeper aquifer enriched the shallow aquifer with Na and Cl ions.

Principal Component Analysis showed that five components (PCs) explain 77% of the total variance of water quality parameters; these are: (1) salinity; (2) water-silicate rocks interaction; (3) hardness due to calcite dissolution, and cation exchange processes; (4) nitrogen pollution; and (5) non-N-related artificial fertilizers. This study demonstrated that the variation of water hydrochemistry in the deltaic plain could be attributed to natural and anthropogenic processes. The interpretation of the PCA results dictated the parameters used for the development of a modified Water Quality Index (WQI), to provide a more comprehensive spatial representation of the water quality of the river delta.

Introduction

Over 500 million people live in river deltas, despite these areas account for only 5% of the global land mass. River deltas are areas of ecological and societal value, because they host fresh surface and groundwater resources, sustain biodiversity, and provide large flat areas for agricultural and urban uses. These multiple conflicting human activities apply significant pressures and risks to deltaic and coastal ecosystems (Kuenzer and Renaud, 2012).

The status of fresh surface water and groundwater quality in the deltaic areas is affected by natural factors, such as the high lateral and vertical granulometric variability of deltaic depositional sequences, the hydrogeochemical reactions between water and sediments and the surface water-groundwater interactions, which modify the hydrochemical characteristics of the surface water and groundwater resources on a spatial and temporal basis (Brunke and Gonser, 1997, Ezzy et al., 2006, Menció and Mas-Pla, 2008, Torres-Rondon et al., 2013).

Seasonal variations of precipitation, river discharge and water table level can cause a reduced replenishment of the water system leading to limited availability of water. Groundwater over-extraction can trigger sea water intrusion, causing a degradation of the deltaic freshwater quality and shortage of drinking water supplies. Nutrients, such as nitrogen and phosphorus, in agricultural practices can contaminate aquifers and surface waters via infiltration and direct runoff, respectively (Barrett et al., 2002, Kim et al., 2009, Mondal et al., 2011, Sarma et al., 1982).

The detailed knowledge of the factors controlling the surface water and groundwater quality is recognized as critical for water resources management, especially in the semi-arid southern coastal parts of Europe (i.e. Mediterranean coast). Conventional hydrochemical methods of data analysis combined with multivariate statistical techniques, such as Principal Component Analysis (PCA), are widely applied in surface and groundwater studies to identify the natural and anthropogenic factors that control water quality (Ahmed Baig et al., 2010, Cloutier et al., 2008, Fan et al., 2010, Matiatos et al., 2014, Okiongbo and Douglas, 2015, Tanasković et al., 2012, Qin et al., 2013, Ujević Bošnjak et al., 2012).

Water Quality Indices (WQIs) are used to describe the overall ‘quality’ of a water body by assigning to a set of critical parameters a single value (e.g. Abbasi and Abbasi, 2012, Debels et al., 2005, Dhanasekarapandian et al., 2016, Şener et al., 2017). The ‘quality’ of a water system can be evaluated in a more easily and rapidly comprehensible manner, assisting decision makers and regulatory authorities to determine priorities and evaluate the impact of various environmental management practices (Pusatli et al., 2009, Sadiq et al., 2010, Song and Kim, 2009). The application of WQIs facilitates the comparison of the water quality between different sampling sites and sampling events in a single or multiple geographical areas.

The deltaic plain of Pinios River lies in central Greece and is of significant ecological importance. It is characterized by rich fresh surface water availability supporting a great biodiversity of flora and fauna. It is classified as “Special Protection Area” of the NATURA 2000 network (GR1420015) and a CORINE biotope (A00020006) and includes riparian forests, an estuary with riparian woodland, marshes, small freshwater lakes, sand dunes and coastal zones. The area combines the natural-biological features of the regions placed under protection by the international treaties of Bonn (Convention on the Conservation of Migratory Species of Wild Animals), Bern (Convention on the Conservation of European Wildlife and Natural Habitats), Barcelona (Convention for the Protection of the Marine Environment and the Coastal Region of the Mediterranean) and Washington (Convention on International Trade in Endangered Species) (Economou, 2005).

This study uses hydrochemical and multivariate statistical techniques and aimed to a) define the possible interactions between groundwater and surface water bodies in the deltaic plain of Pinios River; b) identify the main hydrogeochemical processes and mechanisms that control the water quality in the deltaic environment and the suitability of the water for drinking purposes, and c) test the suitability of a modified Water Quality Index for describing the overall water quality. The major pressures exerted on deltaic aquifers worldwide are reviewed and compared to the results of this study. The outcomes of this work could be easily used by the local authorities, stakeholders and water managers as an operational tool for the effective management of the water resources.

Section snippets

Study area

The deltaic plain of Pinios River (Thessaly, Greece) covers approximately 70 km2, where the river flows in a WSW-ENE direction, discharging into Thermaikos Gulf (Fig. 1). Literature data show that river discharge levels have their maxima between November and April and minima between May and September (Lazogiannis et al., 2014). Before exiting Tempi valley, the river is recharged from karstic spring waters (Fytianos et al., 2002, Migiros et al., 2011). The deltaic plain is characterized by a

Sampling and analytical procedures

Groundwater levels and river water discharge were measured monthly from October 2012 to September 2013. River water discharge (in m3/s) was measured at two river sites, one just before the river enters the delta area (site GA) and one close to the river mouth (site GP, see Fig. 1), using a current flow meter (Valeport BFM 001/002). Groundwater levels were measured in 13 boreholes with a contact gauge (OTT KL 010). RTK-GPS was used to map the position of the boreholes to an accuracy of ∼10 mm.

Hydrological conditions

The temporal variation of groundwater levels in the middle part of the deltaic plain (e.g. P7, P19; Fig. 2a) follows roughly the seasonal patterns of precipitation with higher water table values observed during the wet season and the lower ones during the dry season. In the beginning of the dry season (October–November) water levels of the shallow aquifer were relatively low, increased until February and dropped gradually to reach the lowest values during the end of the dry season

Conclusions

This work presents a regional hydrogeochemical study of the deltaic plain of River Pinios (central Greece), an evaluation of the water quality status and the identification of the main geochemical processes controlling water hydrochemistry and its spatial evolution. The river is primarily recharged by groundwater influxes from the surrounding mountains and secondarily by precipitation and the shallow aquifer inside the deltaic plain.

The results of the Water Quality Index classification showed

Acknowledgements

A significant part of this work was financially supported by project DAPHNE (MIS: 375908), which is co-funded by Greece and the European Union through the O. P. “Education and lifelong learning, 2007-2013” of the Ministry of Education and Religious Affairs. Acknowledgement is given to Mr A. Panagopoulos (PhD), Mr E. Vassilakis (Asst. Professor), Ms D.E. Sifnioti (PhD), Ms D.I. Giannouli (MSc), Mr K. Tsanakas (PhD) and Ms A. Tsoutsia (MSc) for their contribution in the project. We would like to

References (60)

  • R. Qin et al.

    Assessing the impact of natural and anthropogenic activities on groundwater quality in coastal alluvial aquifers of the lower Liaohe River Plain, NE China

    Appl. Geochem.

    (2013)
  • R. Sadiq et al.

    Using penalty functions to evaluate aggregation models for environmental indices

    J. Environ. Manage.

    (2010)
  • Ş. Şener et al.

    Evaluation of water quality using water quality index (WQI) method and GIS in Aksu River (SW-Turkey)

    Sci. Total Environ.

    (2017)
  • T. Song et al.

    Development of a water quality loading index based on water quality modeling

    J. Environ. Manage.

    (2009)
  • I. Tanasković et al.

    Multivariate statistical analysis of hydrochemical and radiological data of Serbian spa waters

    J. Geochem. Explor.

    (2012)
  • L. Torres-Rondon et al.

    An integrative geological and geophysical approach to characterize a superficial deltaic aquifer in the Camargue plain, France

    Comptes Rendus Geosci.

    (2013)
  • M. Ujević Bošnjak et al.

    Hydrochemical characterization of arsenic contaminated alluvial aquifers in Eastern Croatia using multivariate statistical techniques and arsenic risk assessment

    Sci. Total Environ.

    (2012)
  • T. Abbasi et al.

    Water Quality Indices

    (2012)
  • Alexopoulos, J.D., Matiatos, I., Dilalos, S., Poulos, S., 2014. The investigation of the phreatic aquifer development...
  • A.N. Amadi et al.

    Geostatistical assessment of groundwater quality from coastal aquifers of Eastern Niger Delta, Nigeria

    J. Geosci.

    (2012)
  • C.A.J. Appelo et al.

    Geochemistry, Groundwater and Pollution

    (1993)
  • B. Barrett et al.

    Geophysical methods in saline groundwater studies: locating perched water tables and fresh-water lenses

    Explor. Geophys.

    (2002)
  • M. Brunke et al.

    The ecological significance of exchange processes between rivers and groundwater

    Freshw. Biol.

    (1997)
  • Council Directive 98/83/EC of 3 November 1998 on the quality of water intended for human consumption. Off. J. Eur....
  • J.C. Davis

    Statistics and Data Analysis in Geology

    (1986)
  • P. Debels et al.

    Evaluation of water quality in the Chillán River (Central Chile) using physicochemical parameters and a modified Water Quality Index

    Environ. Monit. Assess.

    (2005)
  • Eberts, S.M., George, L.L., 2000. Regional ground-water flow and geochemistry in the Midwest Basins and Arches aquifer...
  • Economou, A., 2005. The coastal zone of the Pinios River delta: development and protection of the environment. Tech....
  • N. El Arabi et al.

    Temporal and spatial change detection of variations in the groundwater composition by multivariate statistical techniques

    N. Y. Sci. J.

    (2013)
  • European Environment Agency, 2015. GIS Map Application: Nitrates in Rivers. Available online at:...
  • Cited by (0)

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