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Isotope Techniques in Flood Analysis
Published in Saeid Eslamian, Faezeh Eslamian, Flood Handbook, 2022
Samir Al-Gamal, Saeid Eslamian
Isotope hydrology addresses the application of the measurements of isotopes from water molecules: the oxygen isotopes (oxygen-16, oxygen-17, and oxygen-18) and the hydrogen isotopes (protium, deuterium, and tritium). These isotopes are the ideal tracers of water sources and movement because they are the integral constituents of water molecules, not something that is dissolved in the water like the other tracers that are commonly used in hydrology (e.g., the dissolved species such as chloride). Water isotopes can sometimes be useful tracers of water flow paths, especially in groundwater systems where a source of water with a distinctive isotopic composition forms a “plume” in the subsurface (see Chapter 18). In most low-temperature environments, the stable hydrogen and oxygen isotopes behave conservatively in the sense that as they move through a catchment, any interactions with oxygen and hydrogen in the organic and geologic materials in the catchment will have a negligible effect on the ratios of isotopes in the water molecule. Although tritium also exhibits an insignificant reaction with geologic materials, it does change in concentration over time because it is radioactive and decays with a half-life of about 12.4 years. The main processes that dictate the oxygen and hydrogen isotopic compositions of waters in a catchment are (1) phase changes that affect the water above or near the ground surface (evaporation, condensation, and melting), and (2) simple mixing at or below the ground surface (Figure 12.1).
Water
Published in P.K. Tewari, Advanced Water Technologies, 2020
In addition to the standard atoms of hydrogen (H, mass 1) and oxygen (O, mass 16), water contains a very tiny fraction of heavier atoms of hydrogen (deuterium H2 and tritium H3) and oxygen (O18), called isotopes. Surface water on earth follows the water cycle, also called the hydrological cycle. Surface water resources (oceans, rivers, lakes, etc.) undergo evaporation, the water vapors thus formed condense as rain (precipitation), the rain waters run to the rivers/oceans as well as to the interior of the Earth, and the cycle is repeated. The larger fraction of the lighter atom evaporates relatively faster than the tiny heavier atom, while in the precipitation stage the heavier fraction comes down first. This subtle phenomenon results in minute differences in the ratio of the heavy to the light atoms of H and O in water in different parts of the water cycle, as well as in the resultant water and its ultimate storage location. In other words, every drop of water carries its own isotopic fingerprints. The minute differences in the isotopic ratio were traditionally measured using mass spectrometers, and useful information on the origin, pathway and age of the water samples was derived. In recent years laser spectroscopy has begun to be used. Such procedures, called isotopic techniques, form the basis of the science called isotope hydrology.
Impact of human activities on urban river system and its implication for water-environment risks: an isotope-based investigation in Chengdu, China
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Chengcheng Xia, Guodong Liu, Yuchuan Meng, Zhengyong Wang, Xiaoxue Zhang
As a practical parameter in isotope hydrology, deuterium excess, defined as d = δ2H – 8δ18O and contains the dual isotopes, has been widely used to identify the water source, quantify water interaction and evaluate the degree of evaporation (Hu et al. 2018; Krishan, Prasad, et al. 2020; Krishan, Singh, et al. 2020b). To reveal the seasonal variation of water evaporation, the monthly mean d-excess of surface water from Nanqiao Channel (i.e., NQ01) and lower reaches of Jiangan River, Qingshui River and Shahe River (i.e., site JA02, QS04 and SH02) is plotted in Figure 8. The d-excess values in river waters are generally higher in the wet season and lower in the dry season, which is directly related to the monsoon-driven moisture source of southwest China. The d-excess of water from JA02 shows the most significant deviation from that of Nanqiao Channel, which can be seen as the water source of the study area, especially during the wet season. The d-excess of water from QS04 and SH02, which flows through dense urban area, is characterized with a slight fluctuation and exhibit similar trends with that of water from NQ01. These observations emphasize the enhancement of water mixing and impair of evaporation caused by urban facilities.
The state of isotope hydrology research in Canada (2007–2022)
Published in Canadian Water Resources Journal / Revue canadienne des ressources hydriques, 2023
Tricia A. Stadnyk, J.J. Gibson, J. Birks, T. L. Holmes
Isotope hydrology, specifically the study of stable isotopes in water (18Ο, 2Η) involves the measurement and detection of small variations in the mass of a volume of water that result from systematic fractionation in the natural environment. Fractionation is the process of mass discrimination that results from temperature and phase changes, or molecular diffusivity. The mass differences between isotopes in water molecules alters water’s boiling and freezing points, ability to evaporate or diffuse in natural systems, and use by and within ecological systems. Consequently, the distribution and fate of water in the hydrologic cycle is impacted in known, specific ways and measured against a global standard regulated by the IAEA. When combined with hydrologic knowledge such as streamflow or precipitation data, the volume of water from a given source can be ascertained. These effective tracers of the water cycle were generally recognized in hydrology in the 1970s, with some of the earliest studies being isotope hydrograph separation (IHS) studies seeking to uncover subsurface contributions to surface water, or runoff by tracing ‘old’ (subsurface or groundwater) and ‘new’ (rain, snow, runoff) water contributions to the hydrograph (Dinçer et al. 1970; Sklash and Farvolden 1979), with earlier studies underpinning the theoretical advances needed to apply tracers at watershed scales (Craig and Gordon 1965; Craig 1961). In Canada, some of the earliest studies in the 1980s similarly focused on HIS, but with the added complexity of integrating cold regions science and snowmelt contributions for isotope tracers (Klaus and McDonnell 2013).