According to a new study published in the AGU journal Earth’s Future, agricultural water shortage is anticipated to worsen across more than 80% of the world’s croplands by 2050. The new study looks at existing and future water needs for global agriculture and anticipates whether available water sources, such as rainwater or irrigation, will be enough to meet those needs when climate change occurs.
To do so, the researchers created a new index to quantify and predict water shortage in agriculture’s two key sources: rain-fed soil water (green water) and irrigation water (blue water) from rivers, lakes, and groundwater.
It’s the first study to use this comprehensive index globally to forecast global blue and green water scarcity due to climate change.
“As the largest user of both blue and green water resources, agricultural production is faced with unprecedented challenges,” said Xingcai Liu, an associate professor at the Institute of Geographic Sciences and Natural Resources Research of the Chinese Academy of Sciences and lead author of the new study. “This index enables an assessment of agricultural water scarcity in both rainfed and irrigated croplands in a consistent manner.”
In the last century, the global demand for water has increased at twice the rate of the human population. Water scarcity is already a problem in agriculture on every continent, posing a serious danger to food security. Despite this, most water scarcity models have failed to include both blue and green water in their analyses.
The percentage of precipitation that is available to plants in the soil is referred to as green water. Green water makes up the majority of precipitation, but it is often disregarded because it is invisible in the soil and cannot be retrieved for other purposes.
The amount of green water available for crops is determined by the amount of rainfall received and the amount of water lost due to runoff and evaporation in a given area. Farming practices, the amount of vegetation in the area, the kind of soil, and the terrain’s slope can all have an impact.
As the largest user of both blue and green water resources, agricultural production is faced with unprecedented challenges. This index enables an assessment of agricultural water scarcity in both rainfed and irrigated croplands in a consistent manner.
Xingcai Liu
The green water available to crops will likely fluctuate as temperatures and rainfall patterns shift as a result of climate change, and farming techniques intensify to fulfill the requirements of a growing population.
Mesfin Mekonnen, an assistant professor of Civil, Construction, and Environmental Engineering at the University of Alabama who was not involved in the study, said the work is “very timely in underlining the impact of climate on water availability on crop areas.”
“What makes the paper interesting is developing a water scarcity indicator taking into account both blue water and green water,” he said. “Most studies focus on blue water resources alone, giving little consideration to the green water.”
According to the researchers, worldwide agricultural water scarcity will deteriorate in up to 84 percent of croplands as a result of climate change, with a loss of water supply driving scarcity in around 60% of those croplands.
Sowing solutions
Changes in available green water as a result of shifting precipitation patterns and increased evaporation owing to increasing temperatures are expected to affect around 16 percent of worldwide croplands. Including this crucial dimension in our knowledge of water scarcity may have ramifications for agricultural water management.
More rain is expected in Northeast China and the Sahel region of Africa, for example, which could assist reduce agricultural water constraint. Reduced precipitation in the Midwest and Northwest India, on the other hand, may lead to increased irrigation to support intensive agricultural.
The new index could aid governments in determining the threat and causes of agricultural water scarcity, as well as developing ways to mitigate future droughts. Agricultural water conservation is aided by a variety of strategies.
Mulching lowers soil evaporation, no-till farming encourages water infiltration, and planting at different times can better match crop development with shifting rainfall patterns. Furthermore, contour farming, in which farmers plow the soil in rows of the same elevation on sloped ground, avoids water flow and soil erosion.
“Longer term, improving irrigation infrastructure, for example in Africa, and irrigation efficiency would be effective ways to mitigate the effects of future climate change in the context of growing food demand,” Liu said.
