Researchers: Lost Freshwater is Serious Concern

Crops forced to switch from irrigation to dryland cropping as water drives up due to climate change.

Published on: Dec 17, 2013

Researchers issued a warning late last week that food production could fall as much as 43% by the end of the 21st Century, but that's not the bad news. In fact, the group from the Computation Institute's Center for Robust Decision Making on Climate and Energy Policy, Argonne National Laboratory, notes that a warming climate will impact fresh water supplies as well.

They note that given current models, there would be added ag losses due to the reversion of 20 to 60 million hectares (about 125 million acres) of currently irrigated fields would revert to rain-fed production.

Agricultural models and hydrological models both incorporate the influence of climate, but are designed by different scientific communities for different purposes. While agricultural models simulate how temperature, precipitation and other climate factors may alter the yield for various crops, hydrological models seek to estimate water-related characteristics such as stream flow, water availability, and storm runoff.

FRESHWATER SHORTAGE? A review of two different climate models raises worries about the availability of irrigation water in the future.
FRESHWATER SHORTAGE? A review of two different climate models raises worries about the availability of irrigation water in the future.

The two models overlap in estimating the amount of water used for ag irrigation, but when researchers fed each type of model with the same climate model forecasts, the models produced dramatically different predictions about future demand for irrigation.

Researchers found discrepancies in how hydrological models use processes such as the carbon cycle and crop water productivity when compared to ag methods.

The comparison also produced new insight about the potential agricultural consequences of climate change. Due to climate change alone, the models predicted a loss of between 400 and 2600 petacalories of food supply, 8 to 43% of present day levels. But due to the decline in freshwater availability -- and the associated conversion of irrigated cropland to rain-fed -- the models predict an additional loss of 600 to 2900 petacalories, the researchers discovered.

While the model shows some areas will be short of fresh water, others may have an excess. The Argonne researchers note that redistributing the excess water to restore or add irrigation to rain-fed crop areas could mitigate some of the consequences of climate change. The researchers say understanding implications of climate change on freshwater availability is critical to future food security goals.