Colorado River Basin farmers will be hardest hit by climate warming, along with food growers in Central Asia and the southern Andes, due to high dependence on shrinking snow as a source of irrigation water, new research has found.
Century-old practices of anticipating drought by monitoring mountain snowpack will be increasingly precarious, researchers also found.
And western agricultural leaders on Monday warned, in letters to President Donald Trump and Congress, that deteriorating pipelines, canals, reservoirs and other water infrastructure threaten the U.S. food supply.
“The western United States is in a tough spot with climate change and changes in snowmelt affecting water resources,” said Colorado State University environmental scientist Nathan Mueller, author of one snowmelt study published Monday in the journal Nature Climate Change.
“But the agriculture in the West is really important for our nation’s food supply. It is imperative to try to adapt to these changes as best we can — and try to limit warming.”
Mountain snowpack has served as a vast natural slow-release reservoir for agriculture, and climate warming leads to less snow and decreasing runoff into streams and rivers. A projected 7-degree spike in temperatures will reduce the contribution of melting snow from 38% to 23% of the water available to grow crops in the Colorado River Basin, the researchers concluded in a global comparative analysis.
In California’s snow-dependent San Joaquin Valley, researchers concluded that warmer temperatures will reduce snowmelt water for irrigation from a 33% share to 18%.
Food production in southern Europe, South America, western China and along the Amu Darya River and across the Tibetan Plateau faces similar hits as snow shrinks and rain in many cases fails to make up the loss, the study found.
More than 2 billion people worldwide depend on water that begins as snow and flows to where they live and work. This research builds on a widening understanding of how climate change impacts on snow are complicating food production.
In Colorado and the West, scientists have determined that water from snow and rain is decreasing along the 1,450-mile Colorado River, which starts in high mountains northwest of Denver and carves canyons up to a mile deep as it flows toward the Gulf of California. Over the past 15 years, a shift toward arid conditions has led to a reduction in Colorado River flows by at least 6%, according to previous CSU and University of Colorado research based on federal hydrology and temperature data.
Yet the river remains the primary water source for an expanding population of 40 million people and 90% of the nation’s winter vegetable production — one of the most over-allocated rivers in the world, with water taken out each year exceeding natural flows. States have been exploring increased conservation as the most feasible, least costly way to minimize draw-down that has left the major reservoirs on the river less than half full.
Shrinking snow as a source of western water means the farmers who grow so much of the nation’s food would have to find alternative water to survive.
“If water is not being supplied by snowmelt, it has got to be supplied by another mechanism,” Mueller said. “It has got to be supplied from reservoir storage months earlier, or increased groundwater pumping, where that is feasible. In some places, it will depend on inter-basin transfers of water.”
A separate study published Monday in Nature Climate Change, led by University of Colorado hydrologist Ben Linveh, looks at the ability to anticipate drought, which for more than a century has been based on mountain snowpack surveys such as those run by the U.S. Department of Agriculture.
Western cities and agriculture water providers have relied on those snow surveys to predict seasonal water availability and give early warnings of droughts — critical for farmers to make decisions.
A shift to less snow wrecks the system. Linveh and fellow researchers conducted their study, using simulations, and concluded that the ability to predict droughts in the West based on snow will decrease by 69% between 2036 and 2065, and by 83% by the end of the century.
“There’s strong consensus that the future will be warmer, and warmer air means precipitation falling less as snow and more as rain. If there’s less snow on the ground, we have less predictive information. Snow is becoming a smaller fraction of the total water budget,” Linveh said. “We need to be able to manage our water differently in drought years and conserve. If we fail to identify a drought, the cost is greater. You limit losses by having lead time.”
On Monday, a Western Growers coalition of 150 agricultural groups — including the Colorado Farm Bureau, the Colorado Fruit and Vegetable Association and several water districts — urged Trump and Congress to address aging western water infrastructure using coronavirus stimulus funds.
Coalition leaders pointed to changing water flows in the West that imperil food production, advising swift repairs and replacements of head gates, pipelines, canals and reservoirs to help producers endure dry times.
“Failing to improve water infrastructure and develop supplies will inevitably result in additional conflict as pressure grows to solve urban and environmental water shortages,” they said in their letter to Congress.
Water conservation, water recycling, watershed management, pipelines, canals, desalination plants, underground reservoirs and surface reservoirs will be necessary, costing billions, the Western Growers contend.
“If and when additional infrastructure funding is discussed as part of a larger economic stimulus package, we need your help to ensure that federal dollars flow to the water infrastructure needs mentioned above.”
Source: Read Full Article