Abstract
This study investigated the relation between long-term changes in springwater temperature and land-use in Tokyo, as well as recent changes in springwater temperature during the period 2006–2011. Field surveys were conducted at 26 springs in Tokyo in both dry and wet seasons.
Long-term changes in springwater temperature were statistically tested at each spring from the end of the 1980s until 2011 using Mann-Kendall rank statistics. Then, the relation between springwater temperature and land-use change was analyzed as follows. First, the recharge area of each spring was estimated by comparing calculated base runoff and observed discharge in the 1990s, along with the distribution of groundwater level in 1968. Next, changes in land-use between 1994 and 2000–2001 at each recharge area were calculated.
A comparison with data obtained before 2006 confirmed that many springs showed a significant upward trend in springwater temperature both in dry and wet seasons. The results showed that the ratio of change from rural land-use to urbanized land-use had a positive correlation with the upward trend of springwater temperature. In addition, a negative correlation was found between the ratio of urbanized land-use in 2000–2001 and an upward trend of springwater temperature. Therefore, the authors concluded that the change of water temperature correlated more strongly with the ratio of change to urbanized land-use, rather than the ratio of urbanized land-use itself.
