Hydrological Simulation And Prediction Based On Multi-source Data In A Glacier Basin

Watershed hydrological model is of vital importance for quantitatively understanding hydrological processes of glacier basins in cold regions.How to use multi-source data to improve its realistic,reduce its uncertainty and improve the future prediction ability are still largely underexplored.Albedo plays an important role in glacier melting process,but there is still a lack of quantitative research considering the effect of albedo on glacier runoff and mass balance simulation.Water stable isotope can reveal the intermediate processes and variables of hydrology in glacier basin,but isotope-hydrological integrated model in glacier basins is still in its infancy,and its universality remains to be tested.Meanwhile,it is essential to integrate and couple glacier hydrological models and glacier response models due to the effects of glacier change on meltwater runoff in the long term.However,domestic research is still in the progress of exploring,and there are great uncertainties in prediction of existing coupled models for glacier changes and the tipping point of meltwater.In this paper,Dongkemadi Glacier basin in the source region of the Yangtze River was taken as an example.Based on the self-developed glacio-hydrological model FLEX^G,albedo and incoming shortwave radiation,and water stable isotope information were integrated into the model to verify its impact on the hydrology process and glacier mass balance simulations in the cold region.Meanwhile,coupled a glacier retreat parameterization method(?h-parameterization)into the glacio-hydrological model(FLEX^G).This study used the future climate change data of the latest 6th International Coupled Model Comparison Program(CMIP6)to drive model,predicting the future changes of the thickness,area and volume of Dongkemadi Glacier and investigating the impact of future climate change and glacier variation on runoff and its peak water.The main conclusions are as follows:(1)Consideration of albedo and incoming shortwave radiation made the glacio-hydrological model FLEX^G perform better in reproducing glacier mass balance,while the simulation of daily runoff was not significantly improved.Similar hydrology process was obtained before and after considering albedo and incoming shortwave radiation.Meanwhile,the runoff in July was closer to the measured value when albedo and incoming shortwave radiation were considered.(2)FLEX^G-iso model reproduced hydrology process,water stable isotope process and glacier mass balance.The introduction of water stable isotopes for model calibration improves the simulation of the runoff process in validation period and the runoff?18O both in calibration and validation period.From the runoff composition of the Dongkemadi basin,meltwater is the main component of runoff by each of the two calibration methods in the ablation season.The contribution of meltwater is about 67.2%by the calibration of runoff data.When using water stable isotope to calibrate the model,the contribution of glacier and snow meltwater is about 58.1%.The water stable isotopes can also improve the simulation of glacier mass balance,especially in 2014,2017 and 2019.(3)The coupled model FLEX^G-?h predicted the changes in ice thickness,glacier area and glacier volume of the Dongkemadi Glacier from 2030 to 2100,and eventually their impacts on water resources.The results show that the glacier would shrink by 8.7×10~8 m~3(74%)on average in volume and 4.9km~2(32%)on average in area at the end of the 21st century under the SSP1-2.6scenario.Under the SSP5-8.5 scenario,the glacier would shrink by 10.8×10~8 m~3(92%)on average decrease and 10.2km~2(66%)on average in area at the end of the 21st century.The glacier runoff may likely reach a peak between 2060 and 2085 under two of both scenarios,which poses a negative impact on downstream water resources after the tipping point(peak water).In this study,based on the FLEX^G model with a flexible structure,the consideration of albedo,incoming shortwave radiation and the water stable isotope improved the glacier hydrological process.In particular,the simulation of glacier mass balance performed better.At the same time,it is found that the FLEX^G model has strong robustness so that simulate the runoff and glacier mass balance well in the absence of albedo and water stable isotopic data.On this basis,FLEX^G-?h model predict the future changes of the Dongkemadi Glacier and investigated the impact of future climate change and glacier variation on runoff and its tipping point.Variation effects on Dongkemadi glacier changes and their hydrological effects.This study provides a more robust tool for the systematic understanding of glacier hydrology processes,and provides scientific support for the formulation of relevant policies and adaptive countermeasures for water resources management in the source region of the Yangtze River.