the rooftop and the lawn, both the valve and pump optimal schedules
switch for less duration than when there is no precipitation
taking place. The solenoid valve switches on at 01:00 h but since
there is precipitation taking place, it switches off in the next sampling
interval. The harvesting of rain water and opening of the
valve cause the height of the water in the tank to rise to 0.57 m.
This precipitation event also causes the water level in the soil to
rise to 29.31 cm. Thereafter the water level remains constant in
both the tank and soil until 03:00 for the tank when the solenoid
next switches on and 03:15 when the pump switches on. The
pump switches off at 03:30 for 15 min enabling the water height
in the tank to reach a peak of 0.93 m. Thereafter the pump switches
on, while the solenoid valve is still filling the tank, until 05.15,
where they both switch off. During this duration, the water height
in the tank drops to 0.23 m while the water level in the soil rises to
29.89 cm. Thereafter, both the solenoid valve and the pump remain
off for the rest of the control horizon. Therefore, the water height in
the tank remain constant at 0.23 m while the water level in the soil
drops due to evapotranspiration losses to 28.73 cm. About 5.9 mm
of water is pumped for irrigation in this scenario.