Have you noticed water sometimes flowing from the small outlet under the stone wall beside Takebashi, on the west side of Palaceside Building where the bridge crosses Kiyomizu Moat? This water is not sewage. It is spring water rising from under the nearby National Archives of Japan and the National Museum of Modern Art, Tokyo.
According to the National Archives, the stacks go down to the fourth basement, and water wells up from below; if left alone, materials would be soaked. So it is stored in a large tank at a depth of about 12–13 meters and pumped out when it reaches a set level. Groundwater fills the tank to overflowing in three or four days, and about 10 tons an hour is discharged from the tank.
The National Museum of Modern Art, Tokyo, has a tank for spring water on the second basement; it is pumped out about once every ten days.
Both send clean groundwater, which may help a little to purify Kiyomizu Moat. Yet, perhaps to avoid the misunderstanding that sewage is flowing from the outlet
under the stone wall, a small sign stands in the planting at the west end of Takebashi: "About the drainage: water from the Kiyomizu Moat outlet is underground spring water from this institution. General Affairs Division, National Archives of Japan, 3-2 Kitanomaru Park, Chiyoda Ward."