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Climate change and population growth are setting the stage for water scarcity in parts of the US well before the end of the century, according to a new study published in the journal AGU. The Future of Earth.
Even efforts to use water more efficiently in municipal and industrial sectors will not be enough to prevent shortages, say the authors of the new study. The results suggest that reductions in water use in agriculture are likely to play the most important role in limiting future water scarcity.
The new study is part of a larger 10-year assessment of the US Forest Service on renewable resources including timber, grassland fodder, wildlife, and water.
"The new study not only provides an estimate of future supply and demand for water, but also looks at what we can do to lessen the projected shortage," said Thomas Brown of Rocky Mountain Research Station in Colorado and lead author of the study . .
To do this, researchers have used a variety of global climate models to analyze future climate scenarios and how they are likely to affect water supply and demand. They also considered population growth.
On the water supply side, the authors used a water yield model to estimate the amount of water that would become available for use across the country and modeled how such water would be supplied for in-stream and off-stream use or stored in reservoirs. for future use.
The new study finds that climate change and population growth are likely to pose serious challenges in some regions of the US, notably in the Central and Southern Great Plains, in the southwest and central states of the Rocky Mountains, and in California, as well as in some areas of the South and Central West.
The core of the new analysis is a comparison of future water supply versus estimated water demand in different water-consuming sectors, such as industry and agriculture.
The study finds that continued reductions in per capita water use rates are likely in most water use sectors but will be insufficient to prevent imminent water shortages due to the combined effects of population growth and climate change.
The authors analyzed a variety of adaptive strategies to alleviate projected water scarcity, such as increasing reservoir storage capacity, pumping more water from underground aquifers, and diverting more water from streams and rivers. Increasing the size of the reservoirs does not seem promising to avoid water shortages, especially in parts of the US that should become drier as climate change advances.
"Where water is the limiting factor, it is unlikely that the reservoir increase will store water," Brown said.
Further reductions in groundwater reserves and greater diversions of in-stream flows could help alleviate future shortages in many areas, but would entail serious social and environmental costs. If these costs are avoided, improvements in irrigation efficiency will need to become a high priority, and additional transfers of water from agriculture to other sectors are likely to be essential, say the study authors.
Brown warns that people should not read too much in the report on their local water supplies. The new study models large river basins and does not observe what will happen in a city or municipality.
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