For the first time, researchers have developed a mathematical equation to describe the impact of human activity on the earth, finding people are causing the climate to change 170 times faster than natural forces.
The equation was developed in conjunction with Professor Will Steffen, a climate change expert and researcher at the Australian National University, and was published in the journal The Anthropocene Review.
The authors of the paper wrote that for the past 4.5bn years astronomical and geophysical factors have been the dominating influences on the Earth system. The Earth system is defined by the researchers as the biosphere, including interactions and feedbacks with the atmosphere, hydrosphere, cryosphere and upper lithosphere.
But over the past six decades human forces “have driven exceptionally rapid rates of change in the Earth system,” the authors wrote, giving rise to a period known as the Anthropocene.
Steffen and his co-researcher, Owen Gaffney, from the Stockholm Resilience Centre, came up with an “Anthropocene Equation” to determine the impact of this period of intense human activity on the earth.
Explaining the equation in New Scientist, Gaffney said they developed it “by homing in on the rate of change of Earth’s life support system: the atmosphere, oceans, forests and wetlands, waterways and ice sheets and fabulous diversity of life”.
“For four billion years the rate of change of the Earth system has been a complex function of astronomical and geophysical forces plus internal dynamics: Earth’s orbit around the sun, gravitational interactions with other planets, the sun’s heat output, colliding continents, volcanoes and evolution, among others,” he wrote.
“In the equation, astronomical and geophysical forces tend to zero because of their slow nature or rarity, as do internal dynamics, for now. All these forces still exert pressure, but currently on orders of magnitude less than human impact.”
Evaporation and transpiration graphic via the USGS
Click here to read the report (Lauren M Foster, Lindsay A Bearup, Noah P Molotch, Paul D Brooks and Reed M Maxwell):
Abstract
In snow-dominated mountain regions, a warming climate is expected to alter two drivers of hydrology: (1) decrease the fraction of precipitation falling as snow; and (2) increase surface energy available to drive evapotranspiration. This study uses a novel integrated modeling approach to explicitly separate energy budget increases via warming from precipitation phase transitions from snow to rain in two mountain headwaters transects of the central Rocky Mountains. Both phase transitions and energy increases had significant, though unique, impacts on semi-arid mountain hydrology in our simulations. A complete shift in precipitation from snow to rain reduced streamflow between 11% and 18%, while 4 °C of uniform warming reduced streamflow between 19% and 23%, suggesting that changes in energy-driven evaporative loss, between 27% and 29% for these uniform warming scenarios, may be the dominant driver of annual mean streamflow in a warming climate. Phase changes induced a flashier system, making water availability more susceptible to precipitation variability and eliminating the runoff signature characteristic of snowmelt-dominated systems. The impact of a phase change on mean streamflow was reduced as aridity increased from west to east of the continental divide.
Oroville Dam spillway collapse. Photo credit Californian Department of Water Resources.
FromThe San Jose Mercury-News (Paul Rogers and Matthias Gafni):
How did a giant, gaping hole tear through the massive Oroville Dam’s main concrete spillway last week, setting in motion the chain of events that could have led to one of America’s deadliest dam failures?
Dam experts around the country are focusing on a leading suspect: Tiny bubbles.
The prospect is simple, yet terrifying and has been the culprit in a number of near disasters at dams across the globe since engineers discovered it about 50 years ago. In a process called “cavitation,” water flowing fast and in large volumes can rumble over small cracks, bumps or other imperfections in concrete dam spillways as they release water during wet years. The billions of gallons of water bumping off the surface at 50 miles an hour create enormous turbulence that can form tiny water vapor bubbles that collapse with powerful force, and like jackhammers, chisel apart concrete.
“It starts with small holes, but it can break off big chunks of concrete,” said Paul Tullis, a professor emeritus of civil engineering at Utah State University and cavitation expert. “It’s like a big grinder. It causes concrete to be torn apart.”
It’s still too early to investigate the cavity on the spillway while dam operators at the nation’s tallest dam desperately drain billions of gallons of water down the damaged chute ahead of coming storms.
Cavitation at the Glen Canyon Dam via Flow Science.
But the same phenomenon nearly caused the collapse of one of America’s other largest dams, Glen Canyon, a 710-foot tall behemoth on the Colorado River, in 1983…
When engineers entered the Glen Canyon Dam’s damaged spillway, they found a crater 32 feet deep and 180 feet long, and tons of concrete, reinforced metal and rock that had simply washed away. The right spillway had similar, but less severe damage.
They didn’t simply reconstruct the spillways, they introduced new technology with aeration slots — essentially ramps at vulnerable spots in the spillway to create an air pocket where water vapor could be disrupted and weakened. The physics gambit worked. In 1984, the runoff was equally as challenging, but Glen Canyon’s spillways had no problems.
Those fixes led the federal agency to retrofit two other large dams — Hoover and Blue Mesa — with aerators.
“It was a defining moment in dam design,” Bureau of Reclamation hydraulic engineer Philip Burgi told a magazine years later. “The world was watching how we were going to solve this problem.”
Similar fixes were added to the Tarbela Dam in Pakistan and Infiernillo Dam in Mexico, and now are common in new dams.
It could be months before the cause of the collapse of Oroville Dam’s spillway is known. The Federal Energy Regulatory Commission this week ordered the state Department of Water Resources to convene a panel of five dam engineering experts to oversee an investigation.
But despite the lessons from Glen Canyon, the Oroville Dam spillway apparently did not have aerators. The massive chute is 178 feet wide, as wide as 15 lanes of freeway, and just 15 inches thick in the middle. Sources at the Department of Water Resources say it hadn’t been retrofitted with aerators — likely one or two ramps, in the case of Oroville’s chute-style spillway, perhaps a foot high each, that would allow the water to flow over and reduce the risk of cavitation.
“Compared to the cost to repair that, it would be just a few million dollars,” said Tullis. “It’s not just a matter of money, it’s a matter of safety. It should have been a priority.”
When the main spillway failed, officials had to slow water releases. The lake, swollen from heavy storms, rose nearly 50 feet in five days and overtopped its emergency spillway for the first time ever, forcing the emergency evacuation of nearly 200,000 residents along the Feather River. The hillside below the emergency spillway eroded badly, leading to fears it would collapse, and send a wall of water into towns below. In recent days, dam operators have increased flows down the broken main spillway, dropping the lake level, and hoping it doesn’t further tear apart.
By Friday morning, state officials had lowered the water level at the 10-mile-long reservoir by 40 feet, especially important as three new storm systems were coming in.
“The threat level is lower. It’s much, much, much lower than what it was on Sunday,” said Bill Croyle, acting director of the State Department of Water Resources.
One concern that is certain to be a focus in the investigation are cracks in the main spillway in recent years. Records from the state Division of Safety of Dams show the cracks were seen in 2009. Also, crack repairs were done last in 2013, according to Kevin Dossey, a senior civil engineer with the Department of Water Resources.
“We made repairs and everything checked out,” Dossey said last Friday at a news conference. “It looked like it would hold, and be able to pass water.”
If the concrete patches came off, or the cracks worsened, however, that could have eroded the spillway, or it could have created enough of an uneven surface to start the domino-effect of cavitaton, experts said.
“It doesn’t take a whole lot of an imperfection when water velocities are very, very high,” said James Kells, a professor of civil and geological engineering at the University of Saskatchewan.
“When I first saw photos, the first thing that came to my mind was cavitation, just because of where the damage was,” Kells said. But he also began to think uneven concrete slabs or internal erosion below the concrete could be “viable causes.”
[…]
Another theory is that the drought dried the ground under the spillway enough that it shrank, creating a void of a few inches that cracked the spillway when huge volumes of water roared down this winter…
1967: Heavy snow melt in the Bighorn River basin raises the Yellowtail Dam reservoir to record levels, opening the spillway for 20 straight days. The Montana dam spillways suffers a hole the size of a semi-truck and trailer.
1977: The Karun Dam in Iran has more than 7,500 feet of concrete torn up on its concrete spillways.
1979: The Kebon Dam along the Euphrates River in Turkey suffers damage to two spillways; one had been running for 15 days, another just three.
1983: The Glen Canyon Dam takes on heavy snowmelt and rains leading to water coming perilously close to the top of the dam. Its two tunnel spillways open for the first time ever and both receive significant damage. Engineers create new aerator devices to fix the problem, a big turning point in spillway engineering.
1983: Hoover Dam, the nation’s most well-known, used its spillways in 1941 for initial testing and again in 1983 due to unanticipated high water levels, and both times a concrete elbow transition suffered cavitation damage.
Mid-1980s: Flaming Gorge Dam on the Green River in northeastern Utah and Blue Mesa Dam in Colorado suffer damage are both fixed with aeration devices.
The city’s denial is its first response in court to a lawsuit that claims discharges of pollutants into Fountain Creek and other tributaries violate the laws. The discharges are from Colorado Springs’ stormwater system…
Colorado Springs asserted in Monday’s filing that it “has at all times been in compliance” with permits issued by the state agency to govern the discharges and the stormwater system.
The city contends it should not be subjected to court orders or monetary penalties that the environmental agencies want a judge to impose.
Colorado Springs also contends that allegations in the lawsuit misrepresent the facts of issues in dispute.
Colorado Springs with the Front Range in background. Photo credit Wikipedia.
The livestock association held its annual meeting at the Cortez Elks Lodge. Local, state and federal officials also spoke at the event, including U.S. Rep. Scott Tipton.
[Ken Curtis] said there is about 300,000 acre-feet of water in the snowpack for the McPhee Reservoir basin. However, but the reservoir will only be able to store about 90,000 additional acre-feet, he said.
“We’re going to get a chance to do a lot of active management,” Curtis said.
With water levels looking good, a recreation spill downriver is likely, but it’s still early, he said. Water officials will have to work hard to manage the above-average snowpack levels this season, he said.
Curtis also discussed the issue of mussels in waterways. The invasive quagga and zebra mussels have infiltrated the Great Lakes and are slowly making their way across the West, he said. Colorado has avoided an infestation, but they have appeared as close as Lake Powell, he said.
If mussels get into waterways on the Western Slope, they could cause costly damage to water infrastructure, such as dams and irrigation equipment, Curtis said.
Recreational boat inspections have been taking place on McPhee Reservoir and House Creek, but funding has decreased for inspections in recent years, he said. Hopefully funding will stabilize soon for the inspections, Curtis said, but in the meantime, access may be limited to recreational areas in 2017.
“We need to raise the insurance one level higher,” Curtis said. “We’re going to close lake access when the inspections aren’t happening.”
McPhee should be open seven days a week, but House Creek will probably only be open four days a week, he said.
Montezuma Valley Irrigation Co., which owns Narraguinnep and Groundhog reservoirs, has also considered closing boat access to both those lakes because of the mussel risk.
The U.S. Forest Service, Bureau of Land Management, Bureau of Reclamation and Dolores Water Conservancy District are raising money to continue boat inspections at McPhee and House Creek, he said.
The boat inspection program costs about $95,000 per year, and the Forest Service previously covered that cost, Curtis said.
No mussels have been found on boats during inspections at McPhee, but they have been found as close as Blue Mesa and Navajo reservoirs, Curtis said.
