And yet Arizona water gurus continue to decree that Arizona has NO immediate water issues…

…And yet Arizona water gurus continue to decree that Arizona has NO immediate water issues…

Climate change to deplete some US water basins, reduce irrigated crop yields    By 2050, the Southwest will produce significantly less cotton and forage, researchers report.

Jennifer Chu | MIT News Office  …  July 11, 2017    agriculture experts finds that certain hotspots in the country will experience severe reductions in crop yields by 2050, due to climate change’s impact on irrigation.

The most adversely affected region, according to the researchers, will be the Southwest. Already a water-stressed part of the country, this region is projected to experience reduced precipitation by midcentury. Less rainfall to the area will mean reduced runoff into water basins that feed irrigated fields.

Production of cotton, the primary irrigated crop in the Southwest and in southern Arizona in particular, will drop to less than 10 percent of the crop yield under optimal irrigation conditions, the study projects. Similarly, maize grown in Utah, now only yielding 40 percent of the optimal expected yield, will decrease to 10 percent with further climate-driven water deficits.

In the Northwest, water shortages to the Great Basin region will lead to large reductions in irrigated forage, such as hay, grasses, and other crops grown to feed livestock. In contrast, the researchers predict a decrease in water stress for irrigation in the the southern Plains, which will lead to greater yields of irrigated sorghum and soybean.

If efforts are made to reduce greenhouse gases and mitigate climate change, the researchers find that water scarcity and its associated reductions in cotton and forage can be avoided.

In the Southwest, water availability for irrigation is already a concern,” says first author Elodie Blanc, a research scientist at MIT’s Joint Program on the Science and Policy of Global Change. “If we mitigate, this could prevent added stress associated with climate change and a severe decrease in runoff  in the western United States. But it will be even worse in the future if we don’t do anything at all.”

Blanc’s study appears in the journal Earth’s Future, and her co-authors are Erwan Monier, a principal research scientist at MIT; Justin Caron, an assistant professor at HEC Montreal; and Charles Fant, a former MIT postdoc.

“A more integrated world”    While many researchers have investigated the effects of climate change on crop yields, Blanc’s study is one of the first to consider how a changing climate may shape the availability and distribution of water basins on which irrigated crops depend.

“Most modeling studies that look at the impact of climate change on crop yield and the fate of agriculture don’t take into account whether the water available for irrigation will change,” Monier says.

In predicting how climate will affect irrigated crop yields in the future, the researchers also consider factors such as population and economic growth, as well as competing demands for water from various socioeconomic sectors, which are themselves projected to change as the climate warms.

“We try to be as representative of reality as possible,” Blanc says.

To do this, the researchers used a model of 99 major river basins in the country, which they combined with the MIT Integrated Global System Model-Community Atmosphere Model — a set of models that simulates the evolution of economic, demographic, trade, and technological processes. The models also include the greenhouse gas emissions and other pollutants that result from these processes, and they incorporate all of that information within a global climate model that simulates the physical and chemical processes in the atmosphere, as well as in freshwater and ocean systems.

“We’re looking at a more integrated world, and how all these interactions will drive changes in irrigation,” Monier says.

“Severely accentuated” shortages    The researchers focused their global simulations on the U. S. and modeled the country’s evolving economic activities in different geographic regions to determine the water requirements for five main sectors: thermoelectric cooling; public supply, such as for drinking water and other public utilities; industrial demand; mining; and irrigation.

They then used a crop model to simulate daily water requirements for various crops, driven by the researchers’ modeled projections of precipitation and temperature, and compared these requirements with the amount of water predicted to be available for irrigation in a particular basin through the year 2050.

“The biggest finding is that it really makes a difference in specific regions, whether you take into account how irrigation availability will change in the future and how that will impact yields,” Monier says.

By 2050, the team projects that, under a business-as-usual scenario, in which no action is taken to reduce greenhouse gases, a number of water basins in the U.S. will start experiencing water shortages. Several basins, particularly in the Southwest, will see existing water shortages “severely accentuated,” according to the study.

The researchers note that the basins that will be the most affected generally do not supply the largest areas of irrigated cropland. For example, though climate change will significantly reduce cotton production in the Southwest, the bulk of the country’s cotton production does not occur in this region.

“It may not matter too much for the total crop production of the U.S., but if you’re a farmer in that particular region that’s going to be impacted, that matters to you,” Monier says. “What we want to do is provide useful information that either farmers or land investors can use to look into the future and make decisions on where is the right region to expand irrigated agriculture, and where is it more risky. We also want to make clear that climate mitigation is better for U.S. irrigated agriculture than not doing anything.”

A climate-changing landscape    Under the same business-as-usual scenario, the researchers projected higher yields for irrigated crops such as wheat, soybean, and sorghum. The increased production in these crops is driven by higher precipitation predicted to occur in the central U.S., combined with higher concentrations of carbon dioxide, which reduces a plant’s water requirements.

The researchers predict that crop yields for wheat, soybean, and sorghum should increase even more if mitigation measures are put in place. In addition to a business-as-usual scenario, the team ran its simulations under two mitigation scenarios, previously proposed by the U.S. Environmental Protection Agency, in which efforts are made to mitigate global warming to 2 and 3 degrees Celsius, relative to pre-industrial times.

They found that both mitigation scenarios should increase yields for all crops compared to the business-as-usual scenario, including cotton and forage, and that the more ambitious scenario has the potential to reduce the number of water-stressed basins.

Going forward, the researchers plan to factor into their simulations various ways in which climate change drives adaptation, and how such adaptations in turn shape crop patterns and the agricultural landscape.

“In the real world, if you’re a farmer and year after year you’re losing yield, you might decide, ‘I’m done farming,’ or switch to another crop that doesn’t require as much water, or maybe you move somewhere else,” Monier says. “That’s the next step: How would the agricultural sector adapt?”

This research was supported, in part, by the U.S. Environmental Protection Agency and the U.S. Department of Energy.


Episode 323: The Ebb and Flow of Water Predictions in Arizona

The state draws closer to an official shortage; techniques for water conservation that start at home.

Monsoon rains should start in Southern Arizona any day now, but the long-term water forecast for the state just got worse.

Snowfall and rain were good this winter in the upper Colorado River Basin, allowing water managers a sigh of relief. The good news didn’t last long, as the amount of water flowing into the Colorado River led the Federal Bureau of Reclamation to change its forecast for the amount of water in Lake Mead, drawing closer to an official shortage.

Such a shortage would mean less Colorado River water for the state, to the tune of about 11 percent.

Some are preparing in advance for the scarcity, and in urban areas, water conservation starts in the laundry room. Learn more about techniques used in urban and rural settings of Southern Arizona to save water and grow food.

On the program

  • Tom Buschatzke, Arizona Department of Water Resources
  • Fernando Molina, Tucson Water
  • Kathleen Marron, rainwater harvester
  • Joaquin Murrieta, Watershed Management Group

New Challenges Emerging In Arizona’s Water Management

By  Steve Goldstein

Published: Friday, July 7, 2017 – 3:10pm

Updated: Friday, July 7, 2017 – 3:17pm


Water management has been a key part of living in Arizona since statehood — and even though leaders in the area have been credited with having a strong vision for maintaining and storing water, new challenges are emerging. Climate change is the one most often mentioned.

But another is the increasing number of people who’ve decided to live in denser communities. With a finite resource like water, is it more difficult to maintain when more residents are using it in a more limited space?

University of Arizona Assistant Professor of Planning and Landscape Architecture Philip Stoker has studied this, and he joined us to talk about his research.

Businesses relieved by elimination of EPA rule

Posted: Jul 09, 2017 10:15 PMUpdated: Jul 09, 2017 10:15 PM    Written By Sam Salzwedel    TUCSON – Many business owners are celebrating the repeal of an environmental regulation.

The Environmental Protection Agency is eliminating the Waters of the United States rule, commonly known as WOTUS.

Tina Thompson’s family has operated a ranch near Willcox since 1879. She recently needed to drill a well. The application to the Arizona Department of Water Resources took 7 days. She said, under WOTUS, she would also need a federal permit.

“If anybody has dealt with federal government and permits they know how lengthy that can be,” Thompson said. “And we just couldn’t wait, for the sake of our cattle, to be able to have water.”

The well is near a wash that runs a few times a year. The ranchers also use heavy equipment to dig out tanks that catch mountain runoff. They bury pipelines, build roads and construct fences. They were afraid all those activities would be limited under WOTUS.

“The Clean Water Act, when it was enacted in 1972, was a good thing,” Thompson said. “We did need some guidance and to keep our waters clean, but this is so broad.”

Rep. Martha McSally helped fight WOTUS. After President Donald Trump was elected she led a congressional letter asking for relief from the new administration.

“We all want to make sure that the waters out there are clean and they are complying with the current law of the Clean Water Act,” McSally said. “And this was being managed mostly by the states previously. And this is just a classic example of over-reach.”

Tucson City Council member Paul Cunningham said the city has made major progress in the past 30 years restoring wells.

“We’ve worked really hard to protect this resource,” Cunningham said. “Like it or not, water is going to be a commodity. It’s not just going to be considered a natural resource.”

He said the WOTUS repeal is an example of special interests influencing Washington.

“To slash and burn the entire policy is a mistake,” he said. “It is irresponsible government, and it is not conducive to protecting the water supply in our state.”

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