The Ministry of Land, Infrastructure, Transport and Tourism said that the water levels in the dams of the dams of the Tonegawa River drainage system, have fallen down due to unusually low rainfall and high temperatures in the month of August. The Tonegawa River serves as a major source of water for the Tokyo Metropolitan area.

The Kanto Regional Development Bureau of the Ministry on September 7, 2012 said that the water storage rate in eight dams in the Tonegawa river system has fallen to 40% which is the third lowest rate ever recorded for the period. The ministry also said that the storage rate was now equivalent to that of 2001 when the water usage restrictions were imposed.

Due to the shortages the bureau called for an emergency meeting this week at which it drew a plan to require residents and businesses in the region to cut their water usage by 10% from September 11, 2012 at 9 am. It at all the restrictions are imposed then it will be for the first time such a step has been taken since until 2001.

The Bureau said that the largest dam in the system the Yagisawa Dam in Gunma Prefecture requires a water level of 816.8 meters above the sea level to supply tap water.