Performance Evaluation Of Hydrological Models In China And Analysis Of Terrestrial Water Storage Changes In North China Plain

Water is the source of all things and is widely used in agricultural irrigation,industrial production,etc.,and plays an important role in human production,life and social development.China is vast and has a large population,and the spatial distribution of terrestrial water storage is uneven.Accurate quantification of China’s terrestrial water storage is essential for the coordinated development of human economy,society and ecological environment.Hydrological models are often used to simulate terrestrial water storage anomalies,which can help humans understand,predict and manage water resources.Different hydrological models use different parameters and model structures,and the simulated water storage are also very different.In this thesis,the GRACE RL06 mascon time-varying gravity field data is used to evaluate the applicability of different hydrological models in nine major river basins in China,which has a positive effect on the improvement of the model and the sustainable development of water resources.The North China Plain is an important industrial and agricultural base and political and economic center in China.Due to the long-term over-exploitation of groundwater in the North China Plain,water resources are facing enormous pressure.Therefore,the research and monitoring of water storage changes in the North China Plain is of great significance to the country’s subsequent management and protection of water resources.The main work of this thesis is as follows:Combined with rainfall and other factors,the changes and causes of terrestrial water storage in China’s nine major river basins were analyzed,and the time-varying gravity field data of the three major institutions were calculated and compared to invert the differences in changes in terrestrial water storage in China.The applicability of six commonly used hydrological models Noah-3.6,CLSM-F2.5,VIC-4.1.2,CLM-4.5,Water GAP-2.2d and PCR-GLOBWB-2 in China’s nine river basins was evaluated using the GRACE RL06 mascon time-varying gravity field model released by CSR(Center for Space Research)and JPL(Jet Propulsion Laboratory)for a total of 144 months from January 2003 to December 2014,and the correlation coefficient,normalized root mean square error and Nash efficiency coefficient were used as evaluation indicators to quantify the hydrological models’ consistency with GRACE mascon data in China’s nine river basins.The snow water and soil water in the southwestern river basins,the Songhua River Liaohe basin and the southeastern river basins have obvious changes.The Noah-3.6 model has relatively good effects on soil water and snow water simulation,and is more applicable;Human activities in the Yangtze River Basin,Haihe-Luanhe Basin,Huaihe River Basin and Pearl River Basin are more obvious.Water GAP-2.2d considers both human activities and model calibration,and its applicability is better than other models;the groundwater changes in the Yellow River Basin are obvious,Water GAP-2.2d and PCR-GLOBWB-2 consider human activities,but PCR-GLOBWB-2 has better applicability,which may be due to the large calibration error of the Water GAP-2.2d model in the Yellow River Basin;the inland river basin is arid and less rainy,and the terrestrial water storage in the northern part of the basin shows a downward trend,and the southern part of the basin shows an upward trend.The applicability of the six hydrological models is poor in the inland river basin.Using the GRACE/GRACE-FO RL06 mascon data released by JPL from 2005 to 2018 to monitor the change of water storage in the North China Plain,it was detected that the terrestrial water storage in the North China Plain showed a downward trend from 2005 to 2018,with a change rate of-2.37±0.06 cm/yr.Based on the inversion of soil moisture data from Chinese regions,we obtained that soil moisture in the North China Plain showed a decreasing trend from2005 to 2018,with a change rate of-0.13±0.03 cm/yr.The spatial and temporal variation of groundwater storage in the North China Plain was quantitatively estimated based on GRACE,and the inversion obtained that groundwater in the North China Plain declined at a rate of-2.2 ±0.06 cm/yr from 2005 to 2018.The spatial and temporal variation of shallow groundwater in the North China Plain was inverted using groundwater wells,and the rate of change was-1.12 ±0.04 cm/yr from 2005 to 2018,and the difference between the two suggests that there may be a deep groundwater deficit in the North China Plain.A comprehensive comparison of the spatiotemporal variation of groundwater in the North China Plain as inferred by the global hydrological model with the GRACE results shows that the CLSM-F2.5 and CLM-4.5 models cannot simulate the groundwater storage variation in the North China Plain well in terms of spatial distribution and numerical values.Water GAP-2.2d can better match the spatial variation of groundwater storage in the actual measured wells,but still overestimate the changes.PCRGLOBWB-2 can better match with the spatial variation of groundwater storage in GRACE,but the value is also overestimated.Using the GRACE/GRACE-FO RL06 mascon observation data to calculate the changes of various components of terrestrial water storage in the North China Plain before and after the South-to-North Water Diversion Project,since the end of 2014,the change rates of terrestrial water,soil water and groundwater have changed from the original-2.09 cm/yr,-0.13 cm/yr,-0.90 cm/yr changed to-0.38 cm/yr,0.38 cm/yr,-0.32 cm/yr.Each water storage has been relieved to some extent,thus indicating that the South-North Water Transfer Project has played an important role in relieving the water storage deficit in the North China Plain.By comparing the changes in terrestrial water storage in the North China Plain monitored by GRACE before and after the South-North Water Transfer with the data on the total water supply from the SouthNorth Water Transfer,the data on the annual groundwater extraction in the North China Plain,and the data on the influence of meteorological factors on the water quality balance,it is found that the differences in the changes in terrestrial water storage are smaller than the sum of the water transfer from the South-North Water Transfer,the reduction in annual groundwater extraction,and the changes in meteorological factors,which may be related to the delay in the rate of change of water storage compared to the water transfer,and the loss of water during the’South Water’ transfer.