FromThe High Country News [August 23, 2021) (Jonathan Thompson):
Climate change and rising demand are sucking the life out of the Southwest’s water supply.
One of the most visible signs of the state of the West’s water supply is the big bathtub ring around the sandstone rim of Lake Powell, the nation’s second-largest reservoir. Whenever the massive hydrological system that delivers water to the lake dwindles, the whitewash halo grows, shrinking only when — or rather, if — that system is replenished by rain and winter snows.
By July 23, the halo occupied some 150 vertical feet of shoreline, showing that the lake’s surface had fallen to its lowest level since 1969, before it was completely filled for the first time. Boat-launch ramps, which had already been extended repeatedly, were finally unusable. The hydropower-generating capacity of Glen Canyon Dam was in danger of disappearing altogether. Even more worrisome, though, is what the diminishing reservoir tells us: The Colorado River watershed is terminally ill.
Two decades of climate change-induced drought and rising temperatures, combined with ever-growing demand, have put the entire water system — and the flora and fauna and more than 40 million people that rely on it — into serious trouble. Now local, state and federal water managers are being forced to reckon with a frightening reality: the incredible shrinking Colorado River system.
The year the Colorado River Compact was signed, divvying up the river’s water between the Upper Basin states — Wyoming, Colorado, Utah and New Mexico — and the Lower Basin — Arizona, Nevada and California.
Proportion of the system’s water that originates in Upper Basin states.
16.52 million acre-feet
The quantity of surface and groundwater withdrawn from the basin in 2010.
13.6 million acre-feet
Amount of that year’s total used for irrigation.
8.62 million acre-feet
The average annual “unregulated inflow” into Lake Powell from 2000-2021. (Unregulated inflow means the approximate natural flow, i.e., the Bureau of Reclamation’s estimate of how much water would run into the lake without upstream diversions or withdrawals.)
3 million acre-feet
Projected unregulated inflow to Lake Powell during the 2021 water year (Oct. 1, 2020, to Sept. 30, 2021).
5.2 million acre-feet
Quantity of water diverted out of the basin and into other watersheds — largely to provide water to urban areas such as Denver, Albuquerque and Los Angeles — in 2010.
Value of hay grown in Colorado River Basin states and exported in 2020, mostly to China and Saudi Arabia.
Consumptive use of Colorado River water for thermo-electric power production (coal and natural gas) in 2010. (Consumptive = water that isn’t returned to the stream after use.)
Approximate amount of water that evaporated from Lake Powell in 2020.
The amount of water that will be delivered to the Colorado River Delta this year for environmental restoration.
25.8 million acre-feet
Amount of water in Lake Powell as of July 14, 1983.
7.9 million acre-feet
Amount of water in Lake Powell as of July 25, 2021.
Map by Alison DeGraff Ollivierre, Tombolo Maps & Design/High Country News
Infographic design: Cindy Wehling. Sources: U.S. Bureau of Reclamation, U.S. Geological Survey, Pacific Institute, U.S. Drought Mitigation Center, Utah Board of Water Resources, Central Arizona Project, Colorado Parks and Wildlife, Colorado Department of Natural Resources, Dolores Water Conservation District.
Jonathan Thompson is a contributing editor at High Country News. He is the author of River of Lost Souls: The Science, Politics and Greed Behind the Gold King Mine Disaster. Email him at firstname.lastname@example.org
On Aug. 18, 2021, the U.S. Environmental Protection Agency announced that it will end use of chlorpyrifos – a pesticide associated with neurodevelopmental problems and impaired brain function in children – on all food products nationwide. Gina Solomon, a principal investigator at the Public Health Institute, clinical professor at the University of California, San Francisco and former deputy secretary at the California Environmental Protection Agency, explains the scientific evidence that led California to ban chlorpyrifos in 2020 and why the EPA is now following suit.
1. What is chlorpyrifos, and how is it used?
Chlorpyrifos is an inexpensive and effective pesticide that has been on the market since 1965. According to the EPA, approximately 5.1 million pounds of chlorpyrifos have been used annually in recent years (2014-2018) on a wide range of crops, including many different vegetables, corn, soybeans, cotton and fruit and nut trees.
Until 2000, chlorpyrifos was also used in homes for pest control. It was banned for indoor use after passage of the 1996 Food Quality Protection Act, which required additional protection of children’s health. Residues left after indoor use were quite high, and toddlers who crawled on the floor and put their hands in their mouth were found to be at risk of poisoning.
2. What’s the evidence that chlorpyrifos is harmful?
Researchers published the first study linking chlorpyrifos to potential developmental harm in children in 2003. They found that higher levels of a chlorpyrifos metabolite – a substance produced when the body breaks down the pesticide – in umbilical cord blood were significantly associated with smaller infant birth weight and length.
These findings touched off a battle to protect children from chlorpyrifos. Some scientists were skeptical of results from epidemiological studies that followed the children of pregnant women with greater or lesser levels of chlorpyrifos in their urine or cord blood and looked for adverse effects.
Epidemiological studies can provide powerful evidence that something is harmful to humans, but results can also be muddled by gaps in information about the timing and level of exposures. They also can be complicated by exposures to other harmful substances through diet, personal habits, homes, communities and workplaces.
3. Why did it take so long to reach a conclusion?
As evidence accumulated that low levels of chlorpyrifos were probably toxic to
humans, regulatory scientists at the EPA and in California reviewed it – but they took very different paths.
At first, both groups focused on the established toxicity mechanism: acetylcholinesterase inhibition. They reasoned that preventing significant disruption of this key enzyme would protect people from any other neurological effects.
Scientists working under contract for Dow Chemical, which manufactured chlorpyrifos, published a complex model in 2014 to estimate how much of the pesticide a person would have to consume or inhale to trigger acetylcholinesterase inhibition. But some of their equations were based on data from as few as six healthy adults who had swallowed capsules of chlorpyrifos during experiments in the 1970s and early 1980s – a research method that now would be considered unethical.
California scientists questioned whether risk assessments based on the Dow-funded model adequately accounted for uncertainty and human variability. They also wondered whether acetylcholinesterase inhibition was really the most sensitive biological effect.
In 2016 the EPA released a reassessment of chlorpyrifos’s potential health effects that took a very different approach. It focused on epidemiological studies published from 2003 through 2014 at Columbia University that found developmental impacts in children exposed to chlorpyrifos. The Columbia researchers analyzed chlorpyrifos levels in the umbilical cord blood at birth, and the EPA attempted to back-calculate how much chlorpyrifos the babies might have been exposed to throughout pregnancy.
On the basis of this analysis, the Obama administration concluded that chlorpyrifos could not be safely used and should be banned. However, the Trump administration halted this decision one year later, arguing that the science was not resolved and more study was needed. The Trump administration subsequently abandoned the human epidemiological studies and reverted to using the Dow-sponsored model and acetylcholinesterase inhibition endpoint that was used back in 2014.
History indicates that both political and scientific considerations likely accounted for the long delays. Although the conclusions clearly shifted with different federal administrations, the epidemiological studies and the acetylcholinesterase model also pointed in different directions – one suggested high health risks in humans, and the other suggested relatively lower risks. Policy conclusions thus depended partly on which data scientists chose as the basis for evaluating health risks.
4. What convinced California to impose a ban?
Three new papers on prenatal exposures to chlorpyrifos, published in 2017 and 2018, broke the logjam. These were independent studies, conducted on rats, that evaluated subtle effects on learning and development.
The results were consistent and clear: Chlorpyrifos caused decreased learning, hyperactivity and anxiety in rat pups at doses lower than those that affected acetylcholinesterase. And these studies clearly quantified doses to the rats, so there was no uncertainty about their exposure levels during pregnancy. The results were eerily similar to effects seen in human epidemiological studies, vindicating serious health concerns about chlorpyrifos.
California reassessed chlorpyrifos, using these new studies. Regulators concluded that the pesticide posed significant risks that could not be mitigated, especially among people who lived near agricultural fields where it was used. In October 2019, the state announced that under an enforceable agreement with manufacturers, all sales of chlorpyrifos to California growers would end by Feb. 6, 2020, and growers would not be allowed to possess or use it after Dec. 31, 2020.
Two months after the California decision, the European Union voted to ban chlorpyrifos due to concerns about neurodevelopmental harm. New York, Hawaii, Oregon and Maryland also moved to end use of the pesticide within their borders. On the same day that California sales of the pesticide ceased, the main manufacturer of chlorpyrifos, Corteva Agrosciences, announced that it would stop producing the chemical.
In late April 2021, a federal court in California ordered the agency to either ban use of chlorpyrifos on food within 60 days or show that it was safe. “The EPA has had nearly 14 years to publish a legally sufficient response to the 2007 Petition,” the ruling stated. “During that time, the EPA’s egregious delay exposed a generation of American children to unsafe levels of chlorpyrifos.”
With the agency’s Aug. 18 announcement, that delay is finally over.
This is an updated version of an article originally published on Jan. 23, 2020.