DRAINAGE DISTRIBUTION AMOUNT DETERMINING METHOD AND DRAINAGE SYSTEM

In a drainage system wherein drain water is collected from a drainage path including a small river, guided to a plurality of drainage pump facilities, and drained into a destination river, a drainage distribution amount is determined for each of the plurality of drainage pump facilities in accordance with an actual precipitation or estimated precipitation, a river water level at a drainage point of each of the plurality of drainage pump facilities is estimated in accordance with the drainage distribution amount and a change in a detected water level at an upstream of the destination river, and the drainage distribution amount for each of the plurality of drainage pump facilities is corrected so as to make the estimated river water level have a value equal to or smaller than an upper limit of the river water level at the drainage point.