Course： Principles of Special Geotechnical Engineering and Water-Rock Interaction
Faculty： Geotechnical Engineering
Practice of Hydrochemistry
Introduction:
Hydrochemistry is the study of the chemical composition of natural waters and the processes that control
their composition. Hydrochemistry provides a valuable tool for understanding the behavior and
distribution of water resources, identifying the sources and processes controlling their composition, and
evaluating their quality and suitability for different purposes. The practice of hydrochemistry involves the
use of various analytical techniques, such as chemical and isotopic analysis, to investigate the chemical
composition and properties of water, and to infer the processes controlling its behavior in the
environment.
This review focuses on providing an overview of the practices of hydrochemistry, with a focus on the
characterization of water in geothermal systems, and to highlight the importance of hydrochemistry in the
sustainable management of water resources, by discussing two recent studies: "Hydrochemistry and
multi-isotope study of the waters from Hanlé-Gaggadé grabens (Republic of Djibouti, East African Rift
System): A low-enthalpy geothermal resource from a transboundary aquifer" by (Awaleha, et al., 2020)
and "Multi-isotopic (O, H, C, S, Sr, B, Li) characterization of waters in a low-enthalpy geothermal system
in Havza (Samsun), Turkey" by (Temizel, Gültekin, Ersoy, & Gülbay, 2021).
Objective:
The objective of the practice of hydrochemistry is to understand the chemical and isotopic composition of
natural waters and to identify the processes controlling their behavior and distribution in geothermal
systems. The first study, conducted by (Awaleha, et al., 2020), investigated the hydrochemistry and multi-
isotope composition of water from the Hanle-Gaggade grabens in the Republic of Djibouti, which is a
low-enthalpy geothermal resource from a transboundary aquifer. The second study, conducted by
(Temizel, Gültekin, Ersoy, & Gülbay, 2021), characterized the multi-isotopic composition of water in a
low-enthalpy geothermal system in Havza, Turkey. The practice of hydrochemistry is an essential tool for
understanding the behavior of water in different hydrogeological settings, and for developing effective
management strategies to protect and sustainably manage our water resources.
The specific objectives of the practices of hydrochemistry are as follows:
1. Identifying the sources and origins of water in different hydrogeological settings, including
geothermal systems, aquifers, and surface waters.
2. Quantifying the concentrations of different chemical species in water, including major and trace
elements, and understanding the processes that control their distribution.
3. Evaluating the hydrogeochemical properties of water, including pH, conductivity, and temperature,
and understanding their role in controlling the behavior of water in different hydrogeological settings.
4. Using isotopic and geochemical tracers to identify the sources of water and to understand the
hydrogeochemical processes involved in water-rock interactions, recharge, and flow.
5. Developing models that can accurately predict the behavior of water in different hydrogeological
settings, including the transport of solutes and contaminants.
6. Assessing the potential impacts of human activities, such as geothermal development and mining, on
water resources and the surrounding environment, and developing appropriate management strategies
to minimize these impacts.
Methodology:
Both studies used a combination of hydrochemical and isotopic techniques to characterize the waters in
geothermal systems. (Awaleha, et al., 2020) analyzed the chemical and isotopic composition of water
samples from the Hanle-Gaggade grabens in Djibouti, while (Temizel, Gültekin, Ersoy, & Gülbay,
2021)analyzed the isotopic composition of water samples from a low-enthalpy geothermal system in
Havza, Turkey, using multiple isotopes (O, H, C, S, Sr, B, Li). They used similar sampling and analytical
procedures, with careful consideration of sample collection, preservation, and storage to ensure the
accuracy and reliability of the results. The interpretation of the data involved the use of various graphical
and statistical tools, such as Piper diagrams, δ18O-δ2H diagram, ternary diagrams, and correlation
analysis, to identify the hydrogeochemical processes and to characterize the sources and behavior of the
geothermal water.
Result:
Some key findings of the two studies on hydrochemistry and multi-isotope analysis of geothermal water
in Djibouti and Turkey are summarized in this section. (Awaleha, et al., 2020) found that the geothermal
water in the Hanle-Gaggade grabens is suitable for low-enthalpy geothermal energy production and it is
characterized by high salinity, with total dissolved solids (TDS) ranging from 400 to 3000 mg/L. The
water is dominated by Na+ and Cl- ions, indicating a sodium-chloride type water. They also identified the
sources and processes controlling the geochemical evolution of the waters, including water-rock
interactions and mixing with other waters.
(Temizel, Gültekin, Ersoy, & Gülbay, 2021) characterized the isotopic composition of the water in the
Havza geothermal system and identified the origin and evolution of the waters. They found that the water
is characterized by high salinity, with TDS ranging from 0.595 to 665 mg/L. The water is dominated by
Na+ and HCO3- ions, indicating a sodium-bicarbonate type water. The results of the study suggest that
the geothermal water is a mixture of shallow and deep groundwater with different isotopic signatures,
indicating different recharge mechanisms and water-rock interactions.
Both studies used multi-isotope analysis to provide a more comprehensive understanding of the
hydrogeochemical processes involved in the formation and evolution of the geothermal water.
Conclusion:
In conclusion, the practice of hydrochemistry plays a critical role in the understanding and management
of water resources, particularly for geothermal systems. The two studies reviewed in this paper highlight
the importance of hydrochemistry in understanding the chemical and isotopic composition of natural
waters and the processes controlling their behavior and distribution in geothermal systems.
Hydrochemical and isotopic techniques provide valuable information on water sources, water-rock
interactions, and recharge mechanisms, which are essential for the sustainable development and
management of water resources. The results of these studies can provide valuable insights for the
sustainable development and management of geothermal energy systems, as well as for the protection of
transboundary water resources. Further research in this area is necessary to fully understand the complex
hydrogeochemical processes involved in geothermal systems and to develop effective management
strategies.
Future research directions:
Future research in hydrochemistry could focus on the development of new analytical techniques and
interdisciplinary approaches to better understand the behavior and distribution of water in the
environment. The integration of hydrochemistry with other fields such as geology, hydrology, and
environmental science could provide a more comprehensive understanding of water resources and their
management. Moreover, more studies on the chemical and isotopic composition of water in geothermal
systems could provide valuable information for the development of sustainable geothermal energy.
References
Awaleha, M. O., Boschettib, T., Adaneha, A. E., Daouda, M. A., Mahdi, A. M., Assowe, D. O., . . . Kadiehd,
I. H. (2020). Hydrochemistry and multi-isotope study of the waters from Hanlé-Gaggadé grabens
(Republic of Djibouti, East African Rift System): A low-enthalpy geothermal resource from a
transboundary aquifer. Geothermics.
Temizel, E. H., Gültekin, F., Ersoy, A. F., & Gülbay, R. K. (2021). Multi-isotopic (O, H, C, S, Sr, B, Li)
characterization of waters in a low-enthalpy geothermal system in Havza (Samsun), Turkey.
Geothermics.
