Impact Assessment of the Urbanization Effects Groundwater Flow and Subsurface Thermal Environment in the Tokyo Bay Area A. Miyakoshi (GSJ, AIST)Y. Sakura (Chiba University) T. Hayashi (GSJ, AIST)V. Monyrath (Chiba University) International Workshop “NEW AND CLASSICAL APPLICATIONS OF HEAT FLOW STUDIES” 4 Oct. 2004

ObjectIndex The aim of this study; To evaluate the impact of urbanization and reclamation upon groundwater and subsurface thermal environment by using observed data of hydraulic head and temperature- depth profiles Keyword; subsurface temperature, groundwater flow, urbanization, reclamation, Tokyo Bay area STEP3 Hydraulic head ⇒ Pumping STEP2 Subsurface temperature ⇒ Pumping ⇒ Natural Groundwater flow STEP1 T-D Profiles ⇒ urbanization ⇒ reclamation (backfill and landfill of waste)

The Kanto Plain is the metropolitan area and the largest plain in Japan (17200km 2 ， 3.96 million people). From the viewpoint of “Groundwater” –Tokyo Bay area is the discharge area of regional groundwater flow system in the Kanto Plain –Pumping was popular until the pumping regulation by the government (1960), and the land subsidence was serious social problem. –After the regulation, the hydraulic head shows the tendency to increase. From the viewpoint of “Urbanization” –The Tokyo Bay area has a long history of urbanization. –Reclaimed land and landfill of waste located in the Tokyo Port. The Tokyo Bay Area

Temperature-Depth profile - Effects of groundwater flow and surface warming- Under the conditions of groundwater flow with surface warming T-D profile records effects of surface temperature change. Surface warming makes the temperature inversion in the T-D profile. In recharge area, the depth of minimum temperature is deeper than discharge area. In the shallow part, T-D profile is strongly affected by surface warming due to recent urbanization. Under the conditions of groundwater flow T-D Profile shows effects of heat advection due to groundwater flow. Discharge type Recharge type Discharge type Recharge type

The comparison of T-D profiles T-D profiles #1: Reclaimed land (Backfill) #2: Landfill of waste #3: Urban area #3 #1 #2

#1 Reclaimed land Surface temperature increase is indicated the less than 0.1 ℃. T-D profile shows typical stable water condition. Reclaimed land (Backfill) Reclamation was completed in Urbanization: nonLand use: park (Unpaved)

#2 Landfill of waste Surface temperature increase is indicated 0.9 ℃, however surface is not urbanized. Effects of surface warming reach to the depth of 40m. Landfill still remain the warming in the shallow part (R and Top of A). Subsurface temperature at the depth of 20m –1982 ： 40.6 ℃ –1999 ： 28.6 ℃ –2003 ： 17.6 ℃ waste effects (not global warming)

#2 Variation of subsurface temperature in Landfill island #2 is located in landfill island of waste. Reclamation was completed in High temperature was observed at the depth of 15m and 20m. This is affected by the heat of decomposition of organic material by microbes (Bureau of Port and Harbor TMG, 2001) 1982: 40.6 ℃ 1999: 28.6 ℃ (Depth: 20m) Temperature shows the decreasing tendency with increasing years.

#3 Urban Area Surface temperature increase was observed 1.9 ℃. This is twice as large as the increase at #2(landfill). Reclamation: non Urban area (Traditional town in Tokyo) Land use: building Effects of urbanization

Pumping Effects On inland side, the total volume of pumping is 4900m 3 /day. On the bay side, the total volume of pumping is 25 m 3 /day. A-A’ cross section (inland – the Tokyo Bay)

Subsurface temperature In the unurbanized area, low-temperature groundwater is recharged from surface to - 50m. In the urban area, high-temperature groundwater is recharged from surface to - 50m. At the deep part (deeper than -100m), the existence of upward groundwater flow toward the part of -100m is suggested. This flow is also controlled by the structure of Tertiary basement. Distribution of subsurface temperature suggests the effects of the human activity and the natural regional groundwater flow. Landfill Urban area Reclamation Subsurface temperature AA’ human activity natural condition

Hydraulic head In the inland side, low hydraulic head is observed at the part between -50 and -100m below sea level. Groundwater flow is concentrated on the low part of hydraulic head from the periphery. Distribution of hydraulic shows the pumping effects at shallow part in the urban area. Hydraulic head Landfill Urban area Reclamation AA’

Conclusion 1.Effects of landfill and urbanization on the T-D profile are decreasing and increasing, respectively. 2.Effects of surface layer to the subsurface temperature distribution is caught in 0 to -100m depth, that tells the natural regional groundwater flow still remain in the deeper part of the urban area. 3.The hydraulic head distribution indicates the proof of groundwater flow estimation from T-D profile and show the impact of pumping (human activity).