Lack of irrigation water poses a threat to farmers in the United States

Agriculture is an important sector of the US economy. Crops, livestock and seafood contribute $ 300 billion annually to the economy. But the sector is highly dependent on the climate, which is already changing due to global warming.

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Many farmers in the western United States rely on snowmelt to help irrigate their crops. According to a new study, due to climate change, the timing and melting of snow can change dramatically.

A team of researchers looked at the monthly demand for irrigation water and snow flow in global pools from 1985 to 2015, hoping to determine where irrigated agriculture depended on past snowfalls and how this could be replaced by higher temperatures.

The next step was to consider possible changes in snowmelt and precipitation if the Earth is heated by 2 or 4 degrees Celsius (about 3 ½ or 7 degrees Fahrenheit), which could potentially raise snow-dependent pools.

According to global data, many pools are at global risk of not having enough water at the right time for irrigation due to changes in snow plaster. Among the most affected, two are the San Joaquin and Colorado River basins in the Western United States.

"In many parts of the world, agriculture depends on the amount of snow that falls at a certain time and on a certain scale," said Yu Qin, lead author of the study. "But climate change will cause more snow and early melting in some pools, which could affect food production."

According to the 4-degree Celsius warming scenario, the researchers found that the share of irrigation water demand in the San Joaquin Basin for snowmelt water decreased by 33 to 18%. The share of demand for snowmelt in the Colorado Basin is reduced from 38 to 23%. Other pools in which agriculture is at particular risk due to changes in snowmelt are located in southern Europe, western China and Central Asia, according to the authors.

Due to its large size and time, rainfall runoff may be able to compensate for the reduction in snow drop runoff to meet irrigation water needs – but only in some pools. "In many pools, further changes in precipitation do not compensate for the melting of lost snow during the growing seasons of crops," the study said.

The researchers looked at the possible availability of reservoir storage and groundwater to help meet the need for additional irrigation created by less snow and early melting. In some pools, these additional requirements pose a major challenge to changing snowmelt.

"Irrigation requirements that are not met by rainfall and snowmelt are currently more than 40 percent of the reservoir's water storage capacity in many Asian and North American basins," said co-author Steve Davis. "And in the warmer world, agriculture will not be the only additional demand for reservoirs and other alternative water supplies, such as groundwater."

The study also looked at which crops were exposed to global threats most of the time as a result of climate change as a result of melting snow. Conclusions showed that rice and cotton in the northern hemisphere, or wheat and managed grass in the spring, were particularly dependent on snow.

The results of the study could be used as a priority and to get information about the methods to reduce the impact of snowmelt change on agricultural water supply, the researchers said. In some cases, policy makers may consider additional pumping of groundwater and the development of a reservoir.

The study was published in the journal Nature.