Abstract
Abstract. Hydrochemical and isotopic techniques have been widely applied in hydrological sciences because isotopic tracers can identify water sources and hydrochemical tracers can discern runoff flow paths. To better understand the hydrological process, we combined hydrochemical and isotopic techniques under controlled experimental conditions to investigate hydrological process from rainfall to runoff in the Hydrohill experiment catchment, a typical artificial catchment in Chuzhou, China. Hydrochemical and isotopic data, i.e., pH, electric conductivity (EC), total dissolved solids (TDS), anions (Cl−, NO3-, SO42- and HCO3-), cations (K+, Na+, Ca2+ and Mg2+) and dissolved Si, 18O and D in water samples were collected during a rainfall event in 2016, and used to determine the hydrochemical and isotopic characteristics of rainfall and runoff components. We applied EC, TDS, SO42-, Ca2+, Mg2+, 18O and D as tracers to investigate rainfall-runoff processes in the experimental catchment. Runoff flow paths could be well identified by the relationship between 18O and EC, TDS, SO42-, Ca2+ and Mg2+. The quantity of flow flux and mass fluxes of main hydrochemical and isotopic tracers gauged at the catchment outlet shows applicable tracers (Ca2+, Mg2+, SO42-, and 18O) are mainly from deep groundwater runoff (from soil layer of 60–100 cm beneath ground surface). Contributions of the event water and pre-event water to the total runoff during the rainfall-runoff process are different. The quantitative results were very encouraging as a basis to develop hydrological models for further study.
Highlights
Runoff sources and their pathways play a significant part in runoff generation and flow concentration, and have been widely studied during the past decades (Zhao, 1989; Gu et al, 2018)
Because the whole depth of Hydrohill is 1m and the groundwater level is higher than 40 cm during this rainfall, SSR100 is regarded as groundwater runoff
Hydrochemical and isotopic methods are effective in tracing water movement from rainfall to runoff components at outlets of an artificial experimental catchment with separate runoff processes
Summary
Runoff sources and their pathways play a significant part in runoff generation and flow concentration, and have been widely studied during the past decades (Zhao, 1989; Gu et al, 2018). Environmental tracers are commonly used on a catchment scale because it is possible to determine the source areas of runoff, flow pathways, residence times and the hydraulic characteristics of flow systems. Hydrochemical indexes such as pH, electrical conductivity (EC), total dissolved solids (TDS) or the concentration of dissolved silicon and various anions and cations (including K+, Na+, Ca2+, Mg2+, Cl−, SO24− and HCO−3 ) have been used to separate and quantify runoff components, so that the contributions of different runoff components can be determined and the hydrological pathways and the solutes sources can be investigated (Pilla et al, 2006; Mul et al, 2008)
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