Use every drop to stave off drought

Irrigation New Zealand warns the irrigation season may shut down six weeks earlier than usual in some regions, threatening the viability of crops and winter feed supply for stock. Earlier forecasts that Lake Opuha in South Canterbury may sustain irrigation until the end of February are now being revisited. 

“The sustained dry conditions have reduced flows in the catchment and increased pressure on our storage prompting us to review the forecast for the lake. River flows and irrigation will suffer when we run out of storage,” says Opuha Water Ltd chief executive Tony McCormick.   

Elsewhere in Canterbury and Otago, water restrictions are biting and many farmers say they need to shut down irrigation four-six weeks early given the dry conditions. This will affect their ability to maintain winter feed crops, sow new pastures and ensure stock are in top condition going into the colder, harsher months.  

IrrigationNZ project manager Paul Reese says irrigators should ensure their equipment is operating at its optimal level so whatever water is pumped is applied effectively. Irrigators also need to be aware of what is happening with their water supply and prepare ahead of further water restrictions to ensure domestic and stock water is still available and that crops can be managed with restricted water supply. 

“Scheduling is key, particularly now irrigators are limited in the water they have through seasonal volumes and with water meters in place, so know your soils and how much water your crop uses and apply irrigation accordingly. Groundwater users in particular need to think about their annual volume and where they are at. 

“Ensure your irrigator is working as it should to guarantee you’re getting the best from the water you apply. Checking pressure and sprinklers regularly is essential.

“If you’re running out of water re-nozzling might help stretch it out for longer or alternatively if you operate a number of irrigation systems think about shutting off the less efficient ones, long laterals in pivot corners for example. That way you can continue to operate more efficient irrigators such as pivots and linear moves for longer,” says Reese.

IrrigationNZ has a checklist of options for irrigators to assist them make the right choices.  The options may not be available to all farmers as they depend on the equipment and setup of each irrigation system and how farmers react will also depend on their particular water restrictions and land use.

“From surface water river takes there may be a rationing regime in place that reduces the water take as certain trigger flows are reached. For example  100L/s to 75L/s when the first threshold hits then from 75L/s to 50L/s with the next. From an irrigation scheme the roster may change from full flow to reduced flow so your system then has to match it or it could be that the scheme provides full flow but on reduced hours or fewer days.”