17:15 〜 19:15
[AHW26-P03] 3D modeling of shallow groundwater-surface water interaction in a land-subsided area in Tokyo, Japan
Land subsidence in the Koto Delta, an area of Tokyo Lowland in Japan, was primarily driven by excessive groundwater extraction in the past, poses multifaceted challenges. Most of the area falls below the average high tide level (Arakawa Peil +2.1m) of Tokyo Bay. Moreover, in response to the threat of flooding, decrease water levels of the eastern rivers though continuously surface water pumping may amplify the peril of seawater intrusion, exacerbating saline water intrusion into subsurface aquifers. The eastern part of the inner river system within the Koto Delta is thought to induce seawater intrusion due to the recharge from Arakawa, potentially impacting adjacent areas. However, this hypothesis requires further numerical simulation and field survey to understand its influence on groundwater dynamics.
To clarify how the inner river system affects groundwater dynamics in coastal aquifer, we present a 3D model of Koto Delta, using HydroGeoSphere, which can solve coupled surface-subsurface flow processes. This model includes manmade facilities, for example, surface drainage and a siphon system connecting the normal water level of the western inland river to the lower water level in the east, as well as the surface and channel roughness coefficients. The initial results suggested that the refined topography of artificial structure has a significant impact on the urban surface water flow and infiltration. Estimated pumped water amount of the eastern rivers covering the period from April 2012 to January 2024 provided by Tokyo metropolitan government, was analyzed and will be further used for the model calibration. According to the collected data, the total pumping amount required to regulate low river water level is not influenced by precipitation, indicating that groundwater recharge may be a contributing factor.
To clarify how the inner river system affects groundwater dynamics in coastal aquifer, we present a 3D model of Koto Delta, using HydroGeoSphere, which can solve coupled surface-subsurface flow processes. This model includes manmade facilities, for example, surface drainage and a siphon system connecting the normal water level of the western inland river to the lower water level in the east, as well as the surface and channel roughness coefficients. The initial results suggested that the refined topography of artificial structure has a significant impact on the urban surface water flow and infiltration. Estimated pumped water amount of the eastern rivers covering the period from April 2012 to January 2024 provided by Tokyo metropolitan government, was analyzed and will be further used for the model calibration. According to the collected data, the total pumping amount required to regulate low river water level is not influenced by precipitation, indicating that groundwater recharge may be a contributing factor.