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Population increases and climate change points to future US water shortages – ScienceDaily

Climate change plus population growth is setting the stage for water shortages in parts of the United States. long before the end of the century, according to a new study in the AGU journal Earth's Future.

Even efforts to use water more efficiently in municipal and industrial sectors will not be enough to put off shortages, say the authors of the new study. The results suggest that reductions in agricultural water use will probably play the biggest role in limiting future water shortages.

The new study is part of a larger 10-year U.S. Forest Service assessment of renewable resources including timber, rangeland forage, wildlife and water.

"The new study not only provides the best guess of future water supply and demand, but also looks at what we can do to reduce projected shortages," said Thomas Brown, of the United States. Forest Service Rocky Mountain Research Station in Colorado and the study's lead author.

To this, the researchers used a variety of global climate models to look at the future climate scenarios and how they will likely affect supply and demand. They also factorized in 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 that water would be delivered to in-stream and off-stream uses or stored in reservoirs for future use.

The new study finds climate change and population growth likely to pose serious challenges in some regions of the US, especially central and southern Great Plains, Southwest and Central Rocky Mountain States, and California, and also some areas of the South and the Midwest.

The core of the new analysis is a comparison of future water supply versus estimated water demand in various water-utilizing sectors, such as industry and agriculture.

The study finds continued reductions in per capita water usage rates are likely in most water use sectors, but will be insufficient to avoid impending water shortages due to combined effects of growth and climate change.

The study's authors looked at a variety of adaptive strategies for alleviating projected water shortages, such as increasing reservoir storage capacity, pumping more water out of groundwater aquifers, and diverting more water from streams and rivers. Increasing the size of reservoirs does not look promising for fending off water shortages, especially in parts of the United States. expected to get drier as climate change progresses.

"Where water is the limiting factor, and the reservoir enlargement is unlikely to store any water," Brown said.

Further reductions in groundwater reserves and greater diversions of in-stream flows could help alleviate future shortages in many areas, but come with serious social and environmental costs. If these costs are to be avoided, improvements in irrigation efficiency will need to become a high priority, and further transfers of water from agriculture to other sectors will likely be essential, say the authors' study.

Brown warns that people should not read too much in the report regarding their local water supplies. The new study models large watersheds and does not look at what will happen on a city or county scale.

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Materials provided by American Geophysical Union. Note: Content can be edited for style and length.

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