About 2 billion people live without safe drinking water and the United Nations has set an ambitious target of ensuring everyone has access to a clean supply by 2030. Each year, as part of its drive to hit that goal, the UN highlights the importance of protecting and improving a safe drinking supply through its World Water Day event. The event encourages people to explore ways to save water and World Water Day 2018, on 22 March, looks at how nature can be tapped to provide solutions.

As agriculture is responsible for 69% of all freshwater withdrawals across the world there is an onus on the industry to do more, especially in providing more efficient irrigation. Growers are responding by adopting frontline technology to work with nature and help them design, operate and maintain more efficient, water-saving systems.

The biggest leap forward has come through the development of Unmanned Aerial Vehicles (UAVs) or drones, fitted with sophisticated imaging systems. Flying at heights of up to 120m enables the grower to map land more accurately and identify natural features like rises and falls in terrain which could otherwise lead to wasteful water run-off. Thermal imaging also highlights areas that can be prone to waterlogging such as pockets of groundwater or changes in soil type.

Armed with this information, an irrigation system and operation plan can be better tailored to reduce water use. With the system operating, regular and frequent overflies can spot leaks and water pooling far more quickly across huge areas that may not have been picked up for hours or even days on some extensive farmland before drones were used.
 
Once the crop is growing the technology becomes even more sophisticated and goes beyond the visible spectrum to identify whether plants have sufficient water or are water-stressed. Every surface reflects some of the light that it receives. In plants the quantity and wavelength of light reflected, is a key indicator of water stress. Healthy plants absorb most of the red light while near infrared light is reflected. In contrast, dead or stressed plant leaves reflect more red light and less near infrared light. But the human eye is sensitive only to wavelengths between 400-700 nm which means the infrared indicators have been routinely missed.

However, drones fitted with multispectral cameras can capture this information. In conjunction with computer software a drone can accurately relay to the grower exactly when and where water is most needed in the crop. Crucially it can also show when crops have sufficient water and it may eventually mean the common sight of irrigators routinely saturating large areas, will become a feature of the past.  In California, where this kind of technology is already being used to spot nature’s otherwise unseen warning signs, water use in state-of-the-art irrigation systems has been reduced by as much as 50%.