Hydrogeochemical and Hydrodynamic Assessment of Tirnavos Basin, Central Greece

Abstract

A combined hydrogeochemical and hydrodynamic characterization for the assessment of key aspects related to groundwater resources management was performed in a highly productive agricultural basin of the Thessaly region in central Greece. A complementary suite of tools and methods—including graphical processing, hydrogeochemical modeling, multivariate statistics and environmental isotopes—have been applied to a comprehensive dataset of physicochemical analyses and water level measurements. Results revealed that the initial hydrogeochemistry of groundwater was progressively impacted by secondary phenomena (e.g., ion exchange and redox reactions) which were clearly delineated into distinct zones according to data processing. The progressive evolution of groundwater was further verified by the variation of the saturation indices of critical minerals. In addition, the combined use of water level measurements delineated the major pathways of groundwater flow. Interestingly, the additional joint assessment of environmental isotopes revealed a new pathway from E–NE (which had never before been validated), thus highlighting the importance of the joint tools/methods application in complex scientific tasks. The application of multivariate statistics identified the dominant processes that control hydrogeochemistry and fit well with identified hydrodynamic mechanisms. These included (as dominant factor) the salinization impact due to the combined use of irrigation water return and evaporitic mineral leaching, as well as the impact of the geogenic calcareous substrate (mainly karstic calcareous formations and dolostones). Secondary factors, acting as processes (e.g., redox and ion exchange), were identified and found to be in line with initial assessment, thus validating the overall characterization. Finally, the outcomes may prove to be valuable in the progression toward sustainable groundwater resources management. The results have provided spatial and temporal information for significant parameters, sources, and processes—which, as a methodological approach, could be adopted in similar cases of other catchments.

Quantitative and Qualitative Methods for the Characterization of Karst Springs (case study: Lorestan province, Zagros Mountain, Iran)

“…In comparison to more homogenous karst aquifer, higher degree of heterogeneity in karst hydraulical characteristics results in rapid changes of spring water quality (Fiorillo and Malik 2019). The mainly hydrochemical analyzes of karst groundwater used in the literature (as summarized in Table 1) including: adopting hydrogeochemical diagrams, e.g., Piper trilinear, Durov and Gibbs (Ghobadi et al 2018;Gao et al 2020;Davraz and Batur 2021;Hoaghia et al 2021); development of hydrochemical indices, e,g., chloro-alkaline and saturation index (Ndoye et al 2018;Hussien et al 2016;Hwang et al 2017Sako et al 2020; statistical methods, e.g., principle factor analysis, cross-correlation analysis, and principal component analysis (Ndoye et al 2018;Sako et al 2020;Vrouhakis et al 2021); and stable isotope analysis (Ghobadi et al 2018;Tang et al 2021). It can be noted that aside from hydrograph and chemograph analysis which usually requires only spring discharge and hydrochemical time-series data, other methods including detailed site-specific speleological investigation (Ford and Williams 2007), tracer tests (Goldscheider and Neukum 2010), hydrograph analysis (Fiorillo 2014) and model ensembles (Fandel et al 2020) are either expensive to implement, time-consuming or require more data input.…”