{"title":"Long-term effects of subsurface structures on groundwater level in a typical urban area of Shanghai, China","authors":"X. W. Wang, Y. S. Xu","doi":"10.1007/s10040-024-02796-w","DOIUrl":null,"url":null,"abstract":"<p>The effect of subsurface structures in blocking groundwater seepage has a long-term influence on groundwater level (GWL). A finite difference method (FDM) model considering the actual distribution of subsurface structures in an urban area of Shanghai (China) was established to predict GWL in the phreatic aquifer (Aq0) and the first confined aquifer (AqI). The equivalent hydraulic conductivity (<i>K</i><sub>eq</sub>) of model elements containing subsurface structures, calculated by the effective medium theory, was applied to the model. The predicted GWL fitted the monitored value in Aq0 well. Additional subsurface structures were added to the model to analyze the influence of the distribution type and the proportion (%) of the volume of subsurface structures that occupy the aquifer (<i>V</i><sub>u</sub>). Four scenarios with different distribution types (concentrated, subconcentrated, subscattered, and scattered) and ten scenarios with <i>V</i><sub>u</sub> varying from 5 to 50%, were analyzed. In all scenarios, the regional average GWL in AqI increased compared to the actual conditions because of the decrease in <i>K</i><sub>eq</sub> and the blockage effect on groundwater flow. The influence of scattered distribution on the regional GWL distribution was the smallest, and the subscattered distribution resulted in the most nonuniform GWL redistribution. The blockage effect of the subsurface structures gradually increased with increasing <i>V</i><sub>u</sub>. The increasing rate of Δ<i>L</i><sub>av</sub> (difference in regional average GWL between the predicted and actual scenarios) becomes considerable when<i> V</i><sub>u</sub> is ~29%. Hence, the projected increase in volume of subsurface structures in AqI under the assumed subscattered distribution is suggested to be <29%.</p>","PeriodicalId":13013,"journal":{"name":"Hydrogeology Journal","volume":"18 1","pages":""},"PeriodicalIF":2.4000,"publicationDate":"2024-05-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Hydrogeology Journal","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1007/s10040-024-02796-w","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The effect of subsurface structures in blocking groundwater seepage has a long-term influence on groundwater level (GWL). A finite difference method (FDM) model considering the actual distribution of subsurface structures in an urban area of Shanghai (China) was established to predict GWL in the phreatic aquifer (Aq0) and the first confined aquifer (AqI). The equivalent hydraulic conductivity (Keq) of model elements containing subsurface structures, calculated by the effective medium theory, was applied to the model. The predicted GWL fitted the monitored value in Aq0 well. Additional subsurface structures were added to the model to analyze the influence of the distribution type and the proportion (%) of the volume of subsurface structures that occupy the aquifer (Vu). Four scenarios with different distribution types (concentrated, subconcentrated, subscattered, and scattered) and ten scenarios with Vu varying from 5 to 50%, were analyzed. In all scenarios, the regional average GWL in AqI increased compared to the actual conditions because of the decrease in Keq and the blockage effect on groundwater flow. The influence of scattered distribution on the regional GWL distribution was the smallest, and the subscattered distribution resulted in the most nonuniform GWL redistribution. The blockage effect of the subsurface structures gradually increased with increasing Vu. The increasing rate of ΔLav (difference in regional average GWL between the predicted and actual scenarios) becomes considerable when Vu is ~29%. Hence, the projected increase in volume of subsurface structures in AqI under the assumed subscattered distribution is suggested to be <29%.
期刊介绍:
Hydrogeology Journal was founded in 1992 to foster understanding of hydrogeology; to describe worldwide progress in hydrogeology; and to provide an accessible forum for scientists, researchers, engineers, and practitioners in developing and industrialized countries.
Since then, the journal has earned a large worldwide readership. Its peer-reviewed research articles integrate subsurface hydrology and geology with supporting disciplines: geochemistry, geophysics, geomorphology, geobiology, surface-water hydrology, tectonics, numerical modeling, economics, and sociology.