Farmers in China are acutely aware of the impact of water shortages. Population growth, increasing urbanisation and industrial water use are all making water shortages more common in China, says Haiyan Xiong, a postdoctoral researcher in plant sciences at the University of Cambridge. Water distribution is geographically uneven, with limited rainfall in northern China and seasonal droughts in southern China.

Much of China’s variable water supply is going to a single crop: rice. About 4,000 litres of water are needed to produce just one kilogram of rice, according to Xiong. Other estimates vary between about 2,500 and 5,000 litres. In China, irrigation for the crop s for about 70% of the total agricultural water use.

One response to this problem has been to look for types of rice that use less water. To this end, thousands of rice varieties are being preserved at the world’s largest rice gene bank, in the Philippines. These include enhanced varieties such as ‘scuba rice’, which can withstand flooding, and the drought-tolerant Sahod Ulan varieties being used by some Filipino farmers.

Xiong and her colleagues hope to combine genome editing with traditional breeding methods to create new drought-resistant varieties. But this is a challenge. “Due to the complexity of the genetic mechanism… not much progress has been made in improving rice drought resistance in China,” she says. “Very few genes can be used in actual production to improve the rice drought resistance.”

Yet the team have identified a single gene in upland rice, known as OsLG3, that’s linked to the length of rice grains as well as drought tolerance. Upland regions, which are dry and hilly, are a much harder environment to grow rice in than lowland paddy fields, and upland rice is usually of lower quality. So introducing the upland drought-tolerance gene into the more widely cultivated lowland rice could allow for the best of both worlds.

Another new type of rice bred for challenging conditions is known as Green Super Rice.

Chinese soil, especially in coastal provinces, naturally contains high amounts of salt, which can become even more concentrated in areas with low rainfall and high evaporation. When there’s too much salt in the soil, plants experience something known as osmotic stress. A large amount of water exits the plant’s cells, causing them to shrink suddenly. The process limits plant growth and productivity.

As with Xiong’s drought-tolerant upland-lowland rice, researchers have found genetic traits in rice varieties that can help Green Super Rice withstand high salt levels and osmotic stress. This often involves backcross breeding, in which genes associated with a desirable trait are bred into a second variety by hybridisation. So far, Green Super Rice appears to produce a high yield in addition to having a high salt tolerance. The hope is that this could open up coastal or other high-salt areas to rice growing.

As well as finding and making new varieties of crops, keeping a keen eye on their fields will help farmers conserve water.

Rice is one of the crops being monitored through Earth observation systems like the EU’s Sentinel missions, which tracked the effects of a drought in the Netherlands in 2018, and Landsat, run by Nasa and the US Geological Survey (USGS). The Landsat programme has launched eight satellites, two of which are currently in orbit.

Landsat captures images in visible light but also using other wavelengths of the electromagnetic spectrum. For instance, it can measure the temperature of land surfaces with its thermal radiation imaging, which has a spatial resolution of 100 metres. This means farmers can see the temperatures of individual fields and estimate how much water they will lose.

Because Landsat has been running for more than 40 years, scientists and water managers can track trends over time. The data has been used to manage water rights between US states, assess how well water conservation measures are working in Ethiopia, and determine where to drill boreholes in Kenya. And, of course, it’s allowed tech-savvy irrigators to determine exactly how much water is being lost from fields, and therefore how much to add.

For instance, Landsat is being used to judge exactly how much water is needed to irrigate water-intensive almond crops in California. In that state’s major irrigation areas, Landsat mapping showed that water management decisions affected water costs (and water savings) more than the climate, according to Gabriel Senay, a research physical scientist with the USGS.

McGlade cautions that this kind of big data should be used in conjunction with, not as a replacement for, farmers’ local knowledge. The Marakwet people of Kenya, for example, have for hundreds of years been dealing with water shortages in ingenious ways, such as communally constructing irrigation furrows on a steep part of an escarpment, and working out complex systems of sharing.

Farmers should be empowered to interpret and make decisions on the basis of Earth imaging, without necessarily leaving this to distant technicians, she believes. The Sentinel and Landsat data are free to access, although some associated tools like OpenET, a digital platform providing automated access to evapotranspiration data, come with a fee.

While the water footprint of meat is much larger than that of rice or other grains, there are ways to make even beef farming less water-consuming.

Charlie Arnott, a beef, lamb and pork farmer in Boorowa, Australia, has seen this firsthand. “I love my grass more than my livestock,” he says, referring to a change he made 15 years ago, following the Millennium drought that devastated southern Australia. Arnott had to sell some of his cattle at a loss, and move others up to 10 hours away in search of feed. He estimates that he lost around AU$300,000 (£125,000/$230,000) because of the drought.

This prompted him to entirely rethink how he managed his land and viewed his animals. Halfway through the drought, he attended a workshop on a method called “regenerative agriculture”. One principle he took away was the importance of valuing natural resources over his livestock, to the point where he now considers himself a sunshine harvester, a water harvester and a grass farmer more than a beef farmer.

In practice, this has meant allowing the grass to rest for three to five months in between short, sharp periods of grazing, moving his livestock frequently. The aim is to let the pasture become as healthy as possible before allowing cattle onto it, while also keeping plenty of ground cover. “That organic matter acts as a sponge,” he says, allowing the soil to absorb rainwater much more than it did under the conventional farming model when the sun would essentially bake the bare ground. Then, there was substantial water runoff to creeks and rivers, eroding the soil as it flowed over it. Now, Arnott has greener pasture, healthier soil that acts as a carbon sink, higher-quality feed and less vulnerability to drought.

There are different names for this simple but effective form of holistic farming: conservation, regenerative, no-till or resource-efficient agriculture. It’s been linked to improved soil moisture in India, lush grasslands in California, and higher farmer incomes in Australia. Proponents of regenerative agriculture believe that its principles can be adapted to just about any farming situation – although research suggests it may be less useful for smallholder farmers.

As the Arnott farm suggests, a more hands-off approach can be remarkably effective for capturing precious water.

These are just some of the many ways farmers and scientists are responding to intensifying water shortages. Others include switching to less thirsty crops, desalinating seawater, harnessing solar power to irrigate crops, collecting water from fog, building sand dams and using even simpler ways of capturing rainwater.

Whether the solution involves technological expertise, traditional knowledge or a combination of the two, it’s clear that human creativity will have to continue to refine our access to water. Without it, we’ll starve.

Image credits: Getty, FAO/Antonello Proto, University of Sheffield, European Space Agency/GeoVille, Charlie Arnott
Graphics sources: Water Footprint Network, Nasa Earth Observatory, University of Sheffield

This article is part of a new multimedia series Follow the Food by BBC Future and BBC World News. Follow the Food investigates how agriculture is responding to the profound challenges of climate change, environmental degradation and a rapidly growing global population.

Our food supply chains are increasingly globalised, with crops grown on one continent to be consumed on another. The challenges to farming also span the world.

Follow the Food traces emerging answers to these problems – both high-tech and low-tech, local and global – from farmers, growers and researchers across six continents.