Hydrological Simulation Traced By Water Stable Isotope And Its Uncertainty Analysis In A Glacier Basin

Uncertainty of hydrological simulation in cold area has long been a bottleneck restricting hydrological development in cold region.Water stable isotope tracing provides important"fingerprint"information for understanding the runoff process of glacier basins in cold regions.But there still lack effective models to couple this information with glacier-hydrological models,and the effect of isotopic information on the uncertainty of glacier basin hydrological models need to be tested as well.In this study,the water stable isotope information(?¹⁸O)is coupled with the glacier-hydrological model FLEX^G,and the coupled modeling of the water stable isotope and runoff process in the glacier basin(FLEX^G-iso)is realized.We taking the Glacier No.1 basin at the headwaters of the Urumqi River as the research area.The runoff,runoff?¹⁸O of Glacier No.1 hydrological section and the glacier mass balance were simulated,and four calibration schemes were designed to compare the impact of the water stable isotope information to the simulation range of the runoff process.Finally,the runoff components based on different definitions are compared and analyzed.The main conclusions are as follows:1)The newly constructed FLEX^G-iso model not only has a good simulation of the runoff process,but also can reproduce important intermediate processes such as water stable isotopes and glacial mass balance.Calibration with multi dataset obtain the smallest range of uncertainty and a good comprehensive simulation.The introduction of water stable isotopes for model calibration improves the reliability of the simulation results and significantly reduces uncertainty.It is worth mentioning that water stable isotopes can also improve the simulation effect of glacier mass balance even if glacier mass balance data is absent for in calibration periods.2)The uncertainty of the parameters obtained only by the calibration of runoff data is relatively large,and the calibration considering the internal data verification can effectively reduce the uncertainty of the parameters.The simulated runoff?¹⁸O showed significant sensitivity to the parameters related to the runoff process and melting process in the glacier baisn.Using the auxiliary data of water stable isotopes improves the identification ability of model parameters,helps to reduce the uncertainty of model parameters,and shows significant restraint ability to the relevant parameters of snow and ice(T_t,C_g,C_wh,F_dd,D and K_f,g).3)The model was applied to the quantitative division of runoff components of the Glacier No.1 hydrological section from 2013 to 2016.Based on the runoff division of water input,the result is:about 37%-45%comes from snowmelt,39%-46%comes from melting ice,and 13%-22%comes from rainfall.Based on the quantification of the runoff components during the runoff process,the results are:31%-33%comes from snowmelt,45%-51%comes from melting ice,0%-15%comes from groundwater,and10%-16%comes from rainfall runoff.Based on the runoff division of different landscapes,the result is:about 80%of runoff from glacier areas,and 20%from non-glacial areas.Water stable isotopes have obvious constraints on the intermediate processes related to snow cover and glaciers,reducing the mutual compromise and uncertainty range of various runoff components in the simulation process.The construction and application of the FLEX^G-iso model is helpful to promote the systematic and quantitative research from observation experiment to process mechanism,and then to mathematical modeling,improving the scientific understanding of hydrological process in cold regions.Using the auxiliary data of water stable isotopes can reduce the uncertainty of the simulation and reduce the compromise between the various components of the runoff caused by the inaccurate parameter identification.The increase in the realistic and robustness of simulation will provide scientific support for the assessment of the impact of climate change on water resources in cold regions,as well as the comprehensive management decisions on the water environment,water ecology,and water disasters in cold regions.