Estimations of the past groundwater recharge rate from deep borehole temperature data Makoto Taniguchi * Department of Earth Sciences, Nara University of Education, Nara 630-8528, Japan Received 23 August 1999; received in revised form 29 November 2000 Abstract In order to estimate the past groundwater recharge rates from deep borehole temperature data, observed temperature – depth profiles are compared with the profiles calculated from heat conduction – convection equation under the condition of linear increase in surface temperature due to global warming and urbanization in Tokyo metropolitan area. The results show the increase in groundwater recharge rate from the 1890s to 1940s, and it decreased from the 1940s to 1990s. These estimations agree well with the precipitation record in Tokyo during the last 100 years. Therefore, the deep borehole temperature data can be used for estimating not only surface temperature history but also the past groundwater recharge rate in Tokyo area. D 2002 Elsevier Science B.V. All rights reserved. Keywords: Borehole temperature; Groundwater recharge rate; Paleohydrology; Climate change; Tokyo metropolitan area 1. Introduction Temperature–depth profiles in deep boreholes are used for estimating ground surface temperature history because the climate change at the ground surface is stored in the underground thermal regime. Birch (1948) was the first person to note that the past climate change can be preserved in the subsurface thermal regime as a deviation from the steady state conditions. Many attempts of climate reconstruction from deep borehole temperature have been made (Lachenbruch and Marshall, 1986; Beck, 1982; Beltrami and Mareschal, 1991; Lewis, 1992; Harris and Chapman, 1995; Bodri and Cermak, 1998). Taniguchi et al. (1997, 1998) and Lewis and Wang (1998) also found the evidence of surface warming due 0341-8162/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved. PII:S0341-8162(02)00008-5 * Tel.: +81-742-27-9202; fax: +81-742-27-9291. E-mail address: makoto@nara-edu.ac.jp (M. Taniguchi). www.elsevier.com/locate/catena Catena 48 (2002) 39 – 51