Abstract
Stable isotopes of O and H in water are meaningful indicators of hydrological and ecological patterns and processes. The Global Network of Isotopes in Precipitation (GNIP) and the Global Network of Isotopes in Rivers (GNIR) are the two most important global databases of isotopes in precipitation and rivers. While the data of GNIP is almost globally distributed, GNIR has an incomplete spatial coverage, which hinders the utilization of river isotopes to study global hydrological cycle. To fill this knowledge gap, this study supplements GNIR and provides a river isotope database with global-coverage by the meta-analysis method, i.e., collecting 17015 additional data points from 215 published articles. Based on the newly compiled database, we find that (1) the relationship between δ18O and δ2H in river waters exhibits an asymmetric imbricate feature, and bifurcation can be observed in Africa and North America, indicating the effect of evaporation on isotopes; (2) multiple regression analysis with geographical factors indicates that spatial patterns of river isotopes are quite different across regions; (3) multiple regression with geographical and meteorological factors can well predict the river isotopes, which provides regional regression models with r2 of 0.50 to 0.89, and the best predictors in different regions are different. This work presents a global map of river isotopes and establishes a benchmark for further research on isotopes in rivers.
Highlights
Stable isotopes in water (δ2 H and δ18 O) have been regarded as a powerful tool for investigating water source, flow paths and transit times [1] and solving large-scale water cycle problems [2].Isotopic composition of water is affected by several environmental factors [3,4] and changes with multiple ecological and hydrological processes [5,6,7]
Abundant information has been added to areas with little or no data coverage in the original Global Network of Isotopes in Rivers (GNIR) database, especially for China, Japan, Canada, Western Europe and Africa
The Global River Water Line shows that the river isotope values do not converge along a single straight line
Summary
Isotopic composition of water is affected by several environmental factors [3,4] and changes with multiple ecological and hydrological processes [5,6,7]. Providing a support for the “two water worlds” hypothesis [12]. Isotopic data in plant xylem water, soil water, stream water, groundwater and precipitation water from 47 globally distributed sites were used to demonstrate that eco-hydrological separation is widespread across different biomes [10], which has been highlighted in many recent experimental or model studies (e.g., the work of measuring and modeling stable isotopes in mobile and bulk soil water conducted by Sprenger et al [11]). These studies provide essentially new insights and evoke new questions for hydrological process understanding
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