Breaking down the mysterious process of artificial irrigation

1 The majority of courses use a 'boom irrigator' to apply water to the track. The boom is essentially a metal bar that stretches across the width of the course with nozzles distributing the water downwards, ensuring the course receives an even covering. The boom is typically set relatively low to the ground – roughly four foot from the surface – and this minimises the risk of wind impacting upon the watering. The boom is either attached to a tractor or a self-propelling hose reel, and the speed at which it covers the ground determines how much water is put down. The slower the boom moves, the more water is applied. Rain guns and sprinklers are also commonly used.

The course at Brighton in the process of being wateredCredit: Brighton racecourse

2 Putting 5mm of water on the course is unlikely to have the same impact as the same amount of rainfall. This is due to evapotranspiration, the process by which water is transferred from land to the atmosphere by evaporation from the soil. The decision to water is usually taken when conditions are warm, so the rate of evapotranspiration is likely to be greater than during natural rainfall, when it is often cooler and cloudier. Watering generally takes place early in the morning, in the evening or during the night to avoid water loss.

3 Newton Abbot last year purchased a new Briggs boom hydraulic irrigation system, with the capability to rise up to ten feet to clear the fences. The cost was £36,000 and it was used extensively in the run-up to their meeting last Tuesday, with more than a million gallons of water being applied to the course in the week preceding the fixture. Watering is a long process. At Brighton it can take nine to ten hours to put 10mm across half the course.