Runoff Response And Adaptive Measures In The Jinghe River Basin Under Changing Environments

The Jing River,as one of the important runoffs into Lake Abbey,can provide a scientific basis for the development and use of water resources and the restoration of the local ecological environment by exploring the evolution of the hydrological processes and the basic laws of the basin under the scenarios of human activities and climate change.In this thesis,we analyse the historical hydrological data and land use changes in multiple periods to clarify the historical change patterns.We construct a SWAT model coupled with a glacier module to simulate the runoff in the upper reaches of the study area through parameterization,and set up a reasonable irrigation system to simulate the irrigation water use process to complete the simulation of the water entering the lake.Using the completed model,the runoff response under climate change and land use change was quantified through scenario setting,and the future runoff evolution of the study area for 2025-2050 was predicted based on two forcing scenarios of CMIP6 climate model SSP245and SSP585.The main findings are as follows:(1)During the period 1958-2018,the average precipitation was 127.1 mm,with annual precipitation concentrated in April-September,accounting for 70.9%of the annual precipitation;precipitation underwent a sudden change in 1980,with an average annual precipitation value of 99.8 mm before the sudden change and 147.0 mm after the sudden change;the multi-year average daily temperature was 8.0°C,with temperatures reaching above 10°C in April-September,and temperatures A sudden change occurred in 1996,with the average temperature before the sudden change being 7.60°C and 8.83°C after the sudden change;the multi-year average annual runoff was 466 million m~3,with June to October runoff accounting for 75.59%of the year and the remaining eight months being above and below 0.2 billion m~3,with no obvious sudden change points.(2)In 2020,compared with 1990,the area of artificial oasis in the study area increased by 738.57km~2,the area of natural oasis decreased by 98.92km~2,the area of low-coverage grassland increased by990.57km~2,the area of glacier decreased by 18.93km~2,and the area of saline land,sandy bare land and Gobi decreased by 517.31km~2 and 1091.67km~2 respectively.(3)The glacier module was embedded in the SWAT model to simulate the runoff process curve of the Jinghe River.After parameter rate determination,the measured monthly average flow at the Jinghe Mountain Outlet Station for the whole period 1972-2017 was 0.78 for NSE,0.47 for RSR,2.13%for PBIAS and 0.79 for R~2 compared with the simulated monthly average flow,and the results were evaluated as excellent through the model.The NSE of the water flow into the lake in the 82nd regiment of the Jinghe plain area was 0.63,RSR was 0.12 and PBIAS was 9.88%,which passed the model evaluation criteria.(4)By changing the original temperature and precipitation,24 climate change series data were generated.The comparison found that for every 1°C increase in temperature,the fluctuation range of runoff growth was between 1.31%and 4.43%,for every 1°C decrease in temperature,the fluctuation range of runoff decrease was between 1.31%and 4.43%,for every 10%increase in precipitation,the fluctuation range of runoff growth was between 12.09%and 13.5%;for every 10%decrease in precipitation,the fluctuation range of runoff was between 3.21%and 7.00%.Based on the distribution of the original land use by category,four scenarios were set up by reclassifying the land use data.The comparison revealed that high mountainous areas of cultured woodland require less water than high cover grassland and can effectively reduce evaporation and increase land infiltration in the watershed.(5)Two scenario concentrations,SSP245 and SSP585,from the CMIP6 climate dataset were selected to construct future meteorological data.The increase in precipitation over the historical period for the two future scenarios ranged from 0.23%to 2.05%,and the increase in temperature over the historical period for the two future scenarios ranged from 2.02°C to 2.34°C.The simulated runoff in the mountains for the two scenarios from 2025 to 2050 was 12.14 m~3/s and 13.83 m~3/s,respectively,a decrease of 17.84%and 6.40%over the historical period.The glacial contribution increased from 25%to 30.44%and 34.69%in the historical period.The volume of water entering the lake in the 82nd Regiment of the Plain decreased by109 million m~3 and 85 million m~3 respectively compared to the historical period.(6)Suggest adaptive countermeasures to the study results.(1)Woodlands should be strengthened in the high mountainous areas.(2)The lakeside area of Lake Ebey should be strengthened with cold,drought and salinity tolerant vegetation,mainly poplar and pokeweed trees.(3)Reduce the total amount of water used in agriculture and continuously optimise the structure of water use.(4)If the main objective is to ensure the surface area of Lake Abbey,the water transferred from outside should be replenished to Lake Abbey by means of canals,pipelines and other conveyance methods.