Multi-scale Optimization Of Sponge City Spatial Based On Surface Water And Groundwater Models

Sponge city is a new generation of urban stormwater management concepts,and it is a new concept and means proposed to deal with urban stormwater management in changing environments.The groundwater aquifer is a natural giant underground sponge facility with the function of storing and regulating stormwater.However,the construction of the sponge city changes the urban rainwater utilization mode and increases the complexity of the interaction between surface water and groundwater.It has led to the neglect of the unique role of existing groundwater aquifers in regulating the water cycle.Focusing on the mechanism of groundwater aquifers in the construction of sponge cities,this study revealed the regulation mechanism of LID(Low-Impact Development)facilities on surface water processes and the response mechanism of groundwater.At the same time,we discussed the optimal configuration of LID facility space and constructed a sponge city research framework considering the properties of groundwater aquifers at different spatial scales.The main contents of this article include:The study built an integrated research framework of "sponge city-groundwater" at multiple spatial scales,and proposed a research method for sponge cities based on numerical models at different spatial scales.This framework conducted hydrological simulations on the sponge city-groundwater at the national scale,city scale,and block scale.Based on the analysis of the simulation results,methods for optimal management at each scale were proposed and demonstrated.In this study,an infiltration potential assessment model based on SWMM-MODFLOW was constructed,and the model was used to study the response of rainwater infiltration to extreme precipitation under different soil properties.Taking the entire Chinese mainland as the research area,we combined Chinese hydrogeological conditions and used the infiltration potential assessment model to quantitatively evaluate the rainwater infiltration potential of the Chinese mainland and the rainwater infiltration potential of representative cities.Subsequently,a strategy for constructing and optimizing the national-scale sponge spatial pattern based on infiltration potential was proposed.The results indicate that cities located in the delta region,such as Tianjin,Suzhou,Shanghai,and Hangzhou,have a weak rainwater infiltration potential.On the other hand,Beijing,Baoding,and Shijiazhuang exhibit a strong rainwater infiltration potential.Due to the diverse geological and topographical conditions in Shenzhen and Guangzhou,the rainwater infiltration potential should be determined based on the specific geological and topographical characteristics of each area.An urban-scale sponge ecosystem optimization method was developed that integrates hydrodynamic models,geographic information system techniques,and Monte Carlo simulations.In this method,factors such as surface water depth,stratum lithology,and groundwater depth were considered comprehensively,and a multi-factor comprehensive evaluation method was used to construct an evaluation system for sponge ecologically suitable areas.In this method,a hydrodynamic model was used to calculate the depth of surface water,the geographic information system technology was applied to quantitatively evaluate the ecological suitability of sponges,and the Monte Carlo simulation was adopted to calculate the uncertainty of the evaluation results and optimize the spatial layout.Taking Shenzhen as the research area,this method was combined with the "matrix-corridor-patch" method of landscape ecology to optimize the spatial structure of the sponge ecosystem.The results indicate the following: Firstly,the distribution of waterlogging depth in Shenzhen is uneven.Areas with waterlogging depths of 0-0.5m can infiltrate and recharge the groundwater without the risk of internal waterlogging,while regions with waterlogging depths exceeding 1.0m are prone to flood risks.Secondly,Quaternary sediments are mainly distributed in alluvial valleys and coastal plains,indicating a strong rainwater infiltration potential in these geological units.High-density granite,due to its compactness,has a lower rainwater infiltration potential.Thirdly,the distribution of groundwater depth in Shenzhen is uneven.In the coastal boundary zone,the groundwater depth ranges from 0 to 3m,with the groundwater level close to the surface and limited storage space.In the foothill zone,the groundwater depth is suitable,serving as a natural water reservoir.A block-scale LID facility optimal configuration method based on surface water-groundwater coupling simulation was developed.In this study,by coupling the SWMM model and the MODFLOW model,a coupled model that can simulate different LID facilities-surface hydrological processes and groundwater response processes was constructed.The model was applied to the Shiyan area of the Xinqiao River Basin in Shenzhen,and the effects of different LID spatial configurations(distributed,grouped,and centralized)on runoff,infiltration,and runoff peak under normal and extreme precipitation were studied.The study quantifies the response process of groundwater level to precipitation under different LID spatial configurations and proposes a method for LID optimal spatial configuration and type selection considering geological conditions and groundwater responses.The results indicate the following: Firstly,the hydraulic conductivity of bioretention facilities has the most significant impact on evaporation,rainwater infiltration,and surface runoff,while the vegetation coverage and hydraulic conductivity of bioretention facilities have the most significant impact on peak flow.Secondly,when the area and type of sponge facilities are the same,decentralized facilities exhibit an increase in total infiltration volume and infiltration delay time with increasing precipitation.The total infiltration volume and infiltration delay time of cluster and centralized facilities remain relatively constant with increasing rainfall,but the infiltration duration of both types increases with higher precipitation.LID(Low Impact Development)facilities can improve the hydrological cycle,and after the addition of sponge facilities,the average groundwater level can rise by 1m annually.This thesis includes multidisciplinary theories of hydrogeology,hydrological simulation,stormwater management,urban and rural planning,and landscape design.From the perspective of groundwater resources protection,we have constructed a multi-scale sponge city research system,coupled with a variety of related technical methods,and applied theoretical and technical methods to practical cases.The rationality and feasibility of theoretical methods and technologies have been verified,and a new perspective and technical guarantee for sponge city management were proposed.