Isotope hydrograph separation in alpine catchments:a review

Isotope hydrograph separation （IHS） is a basic tool in applied hydrology. Its application has expanded to surface water and groundwater interaction, and eco-hydrological processes from runoff generation processes. This paper reviews the progress made in IHS for alpine catchments, with emphasis on its significance in reflecting the impact of global change on water resources. Also, the principle of IHS and its uncertainties are explained in detail. The mechanism of variation of stable isotopes in snow-melt water is discussed, and then methods are presented to improve the separation during snow-melt such as volume weighted average method （VWA）, current melt-water method （CMW） and runoff-corrected event water approach （RunCE）, with their advantages and disadvantages explained. New approaches may extend the applications of IllS, for example, large basin studies combined with GIS, and develop new theories of runoff generation combined with other pararneters such as deuterium excess and DOC.

Chemical characteristics and water stability evaluation of groundwater in the CKDu Zone of Sri Lanka

Groundwater is the main source of drinking water for the rural population in the chronic kidney disease of unknown etiology(CKDu)zone of the North Central Province(NCP)in Sri Lanka.In this study,a total of 334 groundwater samples(311 dug wells,21 tube wells and 2 springs)during the wet season from two aquifers in the NCP were collected,and inves-tigated their chemical characteristics and evaluate their water quality,including ground-water chemistry,main ion sources,the corrosion and scaling potential of groundwater.The results showed that the two hydrochemical types of groundwater in the NCP were mainly of the Ca-HCO_(3),Na·Ca-HCO_(3)types,with the main HCO_(3)−,Na^(+)and Ca^(2+)ions in both types of groundwater originating from silicate and evaporite salt dissolution and influenced by alternating cation adsorption,while the presence of NO_(3)−was mainly anthropogenic.Eval-uation ofwater stability using namely Langelier saturation index(LSI),Ryznar stability index(RSI),Puckorius scaling index(PSI)and Larson-Skold index(LS),indicated that most ground-water presents corrosion potential and has corrosion behavior tendency of metals to some degrees.The water quality of Polonnaruwa was better than that of Anuradhapura in the NCP,and when the groundwater was worse than the“good”grade,which must be properly treated before it is used as drinking water.

Million-year-old groundwater revealed by krypton-81 dating in Guanzhong Basin,China

Groundwater age,defined as the mean subsurface residence time spent isolated from the atmosphere,is of crucial significance for managing water resources and industrial waste.It is also very useful for understanding subsurface contaminant transport,and for paleoclimate reconstruction.It is an important parameter

The elevation gradient of stable isotopes in precipitation in the eastern margin of Tibetan Plateau

Tibetan Plateau(TP)receives moistures from different directions,so variations of isotope elevation gradient on different sides may exist.In this study,we systematically monitored and modeled the elevation effect of stable isotopes in precipitation of the eastern margin of the Tibetan Plateau,where we collected 265 water samples for stable isotope(δ2H andδ^(18)O)analyses,of which 70 are eventful rainfall samples,and 195 are surface water samples,for comparison.Alpine lakes on the mountain peaks were used to reconstruct the average isotope composition of the local precipitation based on the evaporation effect.An elevation gradient of−4.2‰km^(−1)(R^(2)=0.93)was established for the eastern marginal region of TP.This elevation gradient was further confirmed by fractionation assessment using the Rayleigh fractionation model.This is the highest ever reported for the TP and it is the highest as compared to those of all the other slopes as well as that of the interior part of the TP.Precipitation isotopes in the interior of TP show a lower elevation gradient,which is likely caused by significant local moisture recycling.This paper also discusses the limitations of using river water samples to construct the elevation gradient.