Aiming to restore the water levels of springs and rivers, innovative devices are spreading in many Japanese municipalities, including the capital's metropolitan area. One example is a cylinder-shaped device is designed to prevent rainwater on roofs from rushing into drainage, allowing it to permeate into the ground. It was created in the hope of improving the waterside environment, to help prevent land subsidence and droughts caused by a lack of rainwater permeating underground due to urbanization.

The concrete device has many holes and is placed in a hole in the ground approximately 30 centimeters away from the house. The rain gutters of the house are then connected to the cylinder, and rainwater collected in the cylinder gradually permeates into the ground. The 50-centimeter tall cylinder has an internal diameter of 25 to 30 centimeters and allows 294 liters of rainwater to permeate into the ground every hour.

Use of these cylinders is expected to: 1) help prevent land subsidence; 2) preserve and restore groundwater and springs; 3) conserve hydrologic cycles; 4) decrease inflow of rainwater to sewage systems; and ultimately 5) prevent flood damage.

A subsidy program has been set up in almost every municipality that faces depletion of underground water, granting 10,000 to 50,000 yen per unit, depending on the municipality, to those installing the device in their homes. Koganei City in Tokyo, a particularly keen promoter of the device for the last 20 years, has helped install 50,000 units as of April 2006 through its promotion efforts, subsidies and installation advice to home builders and renovators.



Posted: 2007/01/05 05:59:07 PM
Japanese version

TAG Ecosystem , Food/Water , Local government