To provide a rainwater storage facility which has a water storage tank functioning as a water supply tank more efficiently and correctly than ever, and also functioning as a water conservation tank.
In the rainwater storage facility, a pondage control means computes an estimated inflow quantity by using an estimated rainfall and a corrected inflow coefficient. The estimated rainfall is obtained based on meteorological data. The corrected inflow coefficient is obtained by substituting a plurality of latest actual inflow coefficients out of actual inflow coefficients each acquired by dividing an actual inflow quantity during actual rainfall by a total rainwater quantity computed from an actual rainfall, into a preset operational equation. Then stored water in the water storage tank is discharged before raining until a space equal to or larger than a storage space in which rainwater in quantity equal to the computed estimated inflow quantity can be stored, is secured in the storage tank.
HARADA KOJI
NISHII MASAHIRO
