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Tokyo Gov't Experiments with Water-Retentive Pavement and the Heat Island Effect

The Tokyo Metropolitan Government and the Ministry of Land, Infrastructure and Transport have promoted water-retentive pavement and sprinklers placed around the Japanese National Diet Building as ways to counter the heat island effect.

The Tokyo Metropolitan Government and the Ministry of Land, Infrastructure and Transport have promoted water-retentive pavement and sprinklers placed around the Japanese National Diet Building as ways to counter the heat island effect.

Water was sprayed by sprinklers installed on center dividers to offset a shortage of natural rainfall. The water was stored by water-retaining materials mixed into the asphalt pavement. This water in the pavement absorbs heat and lowers the road surface temperature when it evaporates.

The sprinklers used pumped sump water and energy provided by a Hybrid Tower solar/wind power generator.

In the summer of 2005, water was sprayed for about two months, until September 23, on a 350-meter stretch of water-retentive pavement near the Diet Building in central Tokyo. This measure lowered the road surface temperature by approximately 9 degrees Celsius.

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