Irrigation Gate

A watering day on an irrigation system looks like a schedule that keeps breaking itself: the dispatcher spends windows, not litres, because outside a window water never reaches the root.

The first limit is the channel. Capacity is finite and two neighbouring fields cannot be fed by one gate: the field lower along the bed opens only while the upper ones are shut, so while one is watered the other watches its window close on a dry day.

The second is moisture. A field cannot be watered after rain, and midday watering is banned in heat: the water evaporates before the roots and leaves salting and waterlogging on heavy soil. Miss the daylight window and only the night remains.

The third is the night tariff. The pump fills the reservoir while power is cheap, and daytime watering runs on that reserve. Pump too little and the fields miss their norm; pump too much and the bill grows while seepage drains the surplus into the channel for nothing.

The score counts hectares at norm, over-watered area, kilowatt-hours per hectare and lost windows. The field-by-field debrief shows the shortfalls, the surpluses and the water that ran down the bed for nothing.