The planting area under the overpass is dry and dusty. Common rainwater collection and irrigation equipment install water tanks underground. This design collects rainwater on the overpass and stores it in a storage tank on the underside of the bridge, to simulate natural rainwater and return rainwater to plants under the bridge. By raising the tanks to the bridge, the proposal uses gravitational potential energy to replace the electrical energy required by the water pumps, and replaces strong current control with weak current control, which saves energy.