| Xinjiang is one of the major cold regions in China,glacier and snow resources are abundant.Glaciers and snowmelt water are important sources of water supply,and it is accounts for about 30% of annual runoff.With global warming intensifying,it melting speed is increasing,and it's caused significant changes in the hydrological processes of the river,it has had a profound impact on local people's lives,living environment and social economy.Therefore,the study of hydrology in the cold watershed is of great significance.In order to rational knowledge snowmelt runoff law in the alpine region.Improve the water use efficiency and guide rational development and efficient utilization of water resource and provide the basis for disaster mitigation in the area.In this study,the Kashi river basin was taken as the research area,and the hydrological and meteorological data from 1960 to 2005 were taken as the research object.The trend and abrupt change of runoff were analyzed,and the HBV model was constructed using the glacier cataloging data and DEM data,snowmelt runoffs are simulated,and based on the assumptions of climate scenarios,the impact of climate change on flood season runoff is studied.The main research results are as follows:Based on the regular analysis of the flood season runoff,it could be seen that flood-season runoff had tendency of advance from 1960 to 2005,the results of concentration period,concentration degree and variation range have decreased trend from 1960 to 2005.The flood-season runoff had increased tendency from 1960 to 2005,abrupt change of flood-season runoff occurred in 1997.Through analysis find that abrupt change of evaporation and precipitation occurred in 1997.Therefore,it is inferred that the abrupt change of flood-season runoff in 1997 due to the increase of precipitation and the decrease of evaporation after 1997.This study focuses on a HBV model that is equipped with a new glacier module using the DEM data and simulates the glacier and snow melt runoff,based on its glacier inventory dataset and hydrometeorological data from 1990 to 2000.We found out that glaciers exist in the areas of elevation above 2695 m and concentrate on the elevation of 3195?3695 m.The model is calibrated for the period of 1990?1995 and verified for 1996?2000,and its simulations show a good agreement with the runoff measurements,achieving coefficients of determination and efficiency coefficients of 0.86 and 0.83 for the calibration period and 0.83 and 0.80 for the validation period,respectively.Extreme value analysis reveals that in comparison with the measurements,absolute errors in the calculations of maximum and minimum runoffs fall in the range of 0.28?4.57 mm and 0.10?0.17 mm,respectively.The results show good applicability of the HBV model in the study area.Based on the assumed climate scenario data,using the HBV models that have been calibrated and validated,runoff simulations for each scenario,and the impact of climate change on flood season runoff was studied,analyze the change rules of reservoir water storage in advance and postponed under various hypothetical scenarios,as a reservoir full of judgment conditions,multi-year average of flood season runoff in the standard scenario as the standard,1+5% of multi-year average as the upper limit,Use 1-5% of multi-year average as the lower limit.It is found that,When rainfall is constant and temperatures increase by 0.5°C and 1°C,the average increase in runoff is 1.25% and 7.49%,respectively,indicating that the more the temperature rises,the more the runoff increases in the flood season,In order to achieve the reservoir water storage requirements,the less years and the shorter the time for water storage in advance,the more years and the longer the water storage needs to be delayed.When rainfall does not change and the temperature decreases by 0.5°C and 1°C,the average increase in runoff is-9.36% and-12.21%,respectively,indicating that the more temperature decreases,the more the runoff during the flood season decreases.When the temperature is constant and the precipitation increases by 10% and 20%,the average increase in runoff is 5.32% and 15.35%,respectively,indicating that the more precipitation increases,the more the runoff increases in the flood season,the water storage law of the reservoir is the same as the precipitation is constant and the temperature rises at 0.5°C and 1°C;When the temperature is constant and the precipitation decreases by 10% and 20%,the average increase in runoff is-14.28% and-23.95%,respectively,indicating that the more precipitation decreases,the more the runoff during flood season decreases,the water storage law of the reservoir is the same as when the precipitation is constant and the temperature decreases by 0.5°C and 1°C.When rainfall increased by 10% and temperatures increased by 0.5°C and 1°C,the average increase rates of runoff were 11.34% and 17.33%,respectively.This indicates that when temperature and precipitation increase at the same time,runoff in the flood season shows an increasing trend in varying degrees,in order to achieve the requirements for reservoir water storage,a few years need water storage in advance,and most years need to postpone the impoundment;When the precipitation increased by 10% and the temperature decreased by 0.5°C and 1°C,the average increase in runoff was 0.83% and-3.32%,respectively,indicating that the runoff during the flood season was reduced when the precipitation increased and the temperature decreased,but the magnitude was not significant,In order to achieve the reservoir water storage requirements,the year for which water storage is required to be advanced is increased,and the year for which water storage needs to be postponed is reduced.When rainfall decreases by 10%,the average increase in runoff is less than 0,regardless of whether the temperature increases by ±0.5°C or ±1°C,indicating that the runoff in the flood season is reduced,in order to achieve the requirements for reservoir water storage,most years require early storage,and very few years require delays. |
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