| In recent years,with the rapid development of social economy,the hydrological underlying surface has been greatly affected by human activities,and global climate change has also intensified,resulting in obvious changes in hydrological factors such as surface runoff.Among them,rapid urbanization,as a direct exemplification of the impact of human activities on the hydrological underlying surface,increases the impervious area in the watershed,blocks the connection between surface water and groundwater,and has a strong impact on water resources and water environment.As a typical northern city of China,Jinan City has been developing rapidly with the continuous growth of urban area since the beginning of the 21 st century.Simultaneously,the construction of the new urban area for industrial relocation has also been steadily advancing which makes Jinan City a typical rapid urbanization area,and the downstream of the Yellow River Basin where Jinan is located is also a region with strong climate changes in the future.Studying the impact of climate change and urbanization on the hydrological elements of Jinan City can not only grasp the principles of hydrological changes in rapid urbanization areas,but also provide effective support for the reasonable prediction and utilization of future water resources in Jinan City.Jinan has a complicated river network with fuzzy sub-basin boundaries.The meteorological and hydrological monitoring data of Jinan City is also relatively lacking.And the rapid urbanization process that has occurred is strongly affected by policies.Reasonably predicting the future urbanization process of Jinan City by recognizing its development trajectory and obtaining the corresponding climate-driven data are the mainly difficulties of the hydrological element prediction research.In response,this study simulated the underlying surface scenarios and the climate change scenarios by coupling the urban development model and distributed hydrological model and explored the changes of hydrological elements in Jinan under multiple land use and climate scenarios.The main research contents are as follows:1.The study adopted the idea of "model coupling-data fusion-scenario analysis",simulated and predicted the urbanization process of Jinan City,downscaled and corrected the climate prediction data to construct a more accurate analysis and prediction model of hydrological elements in Jinan City.2.Based on the basic data such as land use data and meteorological data in the historical period,the SLEUTH urban development model and SWAT hydrological model were constructed under the premise of fully considering the impact of policies on urban development.The sensitivity parameters of the model are analyzed and identified,and they are calibrated and verified using model evaluation indicators.3.Based on the four sets of land use data and other data from 2000 to 2015,combined with policy impacts,the land use changes in Jinan City in the future are predicted.The results show that the predicted area of Jinan City in 2030 is 640 km2,with an increase of 170.66%over 2000.The surface runoff of the whole basin will increase by 28.5%,and evaporation and infiltration will decrease by 1.56%and 4.9%respectively with the urbanization process from 2000 to 2030.The surface runoff is the most sensitive to land use change among the studied hydrological elements,which had increased even more than 40%in some core urbanization sub-basins.4.The CMADS meteorological data set was used to downscale and correct the CMIP5 model data,and the change trend of climatic factors such as precipitation and air temperature under three climate scenarios in Jinan City was obtained.Driven by the hydrological model,it was found that the precipitation in 2006-2035 under the RCP2.6(low greenhouse gas emission intensity)scenario showed an increasing trend,while the RCP8.5(high emission intensity)showed a decreasing trend.5.The four phases of land use scenarios from 2000 to 2030 at 10-year intervals were combined with three climate scenarios of RCP2.6,RCP4.5,and RCP8.5 for combined analysis.The results of changes in hydrological factors such as total runoff in 12 combined scenarios are obtained,and the contribution of climate change and land use change to runoff is analyzed,while climate change has a greater impact on runoff than landuse change under high-emission scenarios.The results also show that the depth of total runoff in core urbanized areas is greater than Other areas in multiple scenarios which could reaches more than 360mm and therefore increases the risk of flood disasters.And the combination of 2030 land use scenario and high greenhouse gas emission scenario may reduce the total runoff by more than 14%,while the surface runoff is still increasing,which would force Jinan City to face the double risks of water shortage and flood disaster.It is recommended that Jinan City focus on flood control management and strengthen low-impact construction in the future. |
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