The High-Stakes Math
by Jon Bruner
In a darkened, ultra-secure room on the fifth floor of an unassuming office tower in Portland, Ore., Bob Neal sits before a panel of ten computer screens and plays Moses. It's 8:45 in the morning on a sunny late-August day and electricity demand is rising as office workers across the West switch on their computers. Neal points to a dense blue-and-white display whose flickering numbers show power output at each of 31 dams in the Columbia basin. With a few keystrokes he orders the Grand Coulee Dam, the continent's largest power plant, to ramp up its output by 870 megawatts in the next hour -- an increase enough to light 15 million light bulbs at 60 watts apiece.
240 miles away, the Grand Coulee's 24 giant turbines ease open, sending a surge of water toward the Pacific Ocean. Just below the dam, the river quadruples in volume and rises by 13 feet over a period of nine hours. By 2 P.M., one and a half million gallons of water -- enough to flood a football field three feet deep -- moves through the dam's turbines every second.
The Columbia is a river of colossal proportions: it's the most voluminous in the West, draining an area the size of Texas and each year passing 60 cubic miles of water to the Pacific Ocean. The 14 structures that harness it are equally formidable: a dam is likely to be the largest manmade object, the most exuberant feat of engineering that you'll ever see, and the Columbia's are among the world's biggest. But as large as the dams are, their margins are minuscule and operating them takes unerring foresight and subtle management: let too much water fill reservoirs and a rainstorm might flood Portland; keep the reservoirs too empty and you'll parch farmers. Send too much water over a dam's spillway and you'll suffocate fish with dissolved gases; send too much through its turbines and you'll overload the electrical grid.
The Columbia River basin is home to more than 100 large dams and hundreds of smaller installations. Diagram courtesy U.S. Army Corps of Engineers.
Those margins are doubly difficult to master given the temperamental pulse of a river whose volume increases by a factor of five every spring as snow melts in the Rockies. Within the river's seasonal changes come manmade fluctuations: every morning its dams awaken the Columbia with surges of water to satisfy the Northwest's demand for electricity, and every evening the dams tighten their gates to put the river back to sleep. And every other second, an automated system assesses the supply of electricity against demand and makes tiny adjustments to the volume of water moving through each dam's turbines.
The Bonneville Dam's Powerhouse No. 1 is a thousand-foot-long, depression-era edifice that bristles with electrical transformers and transmission lines. It sits astride the Columbia River, which loses as much as 70 feet of elevation as it falls through the building's turbines and emerges, almost glass-smooth, in the powerhouse's tailrace. In the generator room, a space so long that its horizontal lines converge and fade into the distance, ten school-bus-sized generators hum quietly. "It's big, isn't it?" says Jim Duffus, the power plant's ebullient, moustachioed manager, as he strides down the broad corridor. Duffus started out as an electrician's apprentice in the Panama Canal Zone, and his enthusiasm for all things electric and for the scale of the place emerges in his narrative. That's not just a circuit breaker; it's a five-ton circuit breaker.
Each generator housing contains a 280-ton turbine that looks like a ship's propeller and a 430-ton generator rotor that spin in perfect synchronization with the grid's alternating current. As large as these generators are, they're among the nimblest big sources of power available: Duffus can bring a turbine online in under two minutes and, once it's running, can summon as much electricity from it as he needs in as little as ten seconds. Each 60-megawatt generator can produce enough electricity to supply roughly 60,000 households, but all of that capacity isn't needed most of the time.
Duffus suggests an analogy: imagine a giant cogwheel in the sky, to which every generator and power user in the country is connected. The generators exert force against the wheel to turn it, and customers draw force from it to run light bulbs, toasters and air conditioners. Each generator in this scenario is locked into synchronization with the other generators: push too hard against the cogwheel, and the wheel pushes back. But if too many generators are supplying too much force to the cogwheel, some generators connected to it will be pushed along with the wheel, effectively becoming motors.
So overgeneration is a key concern to the operators of the power plant and the grid: those five-ton circuit breakers stand ready to disconnect any generator from the grid should supply exceed demand by a dangerous margin, and the Bonneville Power Administration puts enormous effort into meeting demand through forecasting and constant measurement and by selling electricity over an enormous area: power from the Columbia's dams can be sold as far away as southern California via a million-volt direct-current line that slices across the Nevada desert from The Dalles, Ore., to Los Angeles.
The Bonneville Dam is a run-of-the-river structure: rather than impounding a large reservoir, like the Hoover or Grand Coulee dams, it passes water through largely as it receives it. If Bonneville were to close all of its gates during high spring runoff, water could reach the top of the dam in as little as six hours. That means water has to go somewhere when it reaches the dam, and if electricity demand isn't high enough to run it through the power plant, it goes over the spillway instead -- 18 gates weighing 350 tons apiece that can pass 13 million gallons of water per second.
Standing in front of the spillway is a stirring experience: the sound of millions of gallons of water sloshing over a six-story-high sill is thunderous. A cloud of water vapor rises from the dam and the river doesn't return from frothy white to languorous brown for more than a mile downstream. Running water over the spillway heats the river, since it sends warm water downstream from the top of the reservoir, and the relentless churn at the bottom of the dam aerates the river as well, mixing nitrogen into the water. Neither is very good for the millions of fish that swim down and up the river every year.
Everything at the dam is measured, counted, tabulated and stored: volume of water running over and through the dam; elevation of the water in the forebay and tailrace; power generated; water temperature; gas content; precipitation; ground moisture. Even fish throughput is carefully counted by attendants sitting in darkened rooms behind windows at the dam's fish ladders -- 3,939,524 fish swam upstream past Bonneville Dam in 2010, including 809,512 adult Chinook salmon and 11,183 lampreys. (On their way upriver, fish go through the ladders; heading downriver, they go over the dam's spillway, through its turbines -- where, astonishingly, 96% of them survive the trip -- or through a bypass tube that spits them out two miles below the dam. Hungry birds have figured out that the disoriented fish pouring out of the tube are easy prey, but the U.S. Army Corps of Engineers, which owns the dam, has figured out the birds: it wards them off with a water cannon that sits on top of the tube.)
For all the complexity and high stakes that the Bonneville Dam encounters, they're dwarfed by the complexity and high stakes of operating 27 big dams on the Columbia and Snake rivers together -- a task that falls to a collection of agencies including the Corps, the BPA, the Bureau of Reclamation, a handful of public utility districts and their Canadian counterparts. The dam owners abide by a 1964 agreement that coordinates their management of the river. Before then, says Barton, "run-of-river dams were feast or famine." Sometimes the upstream dams would pass much more water than they could handle and they'd have to spill it. Other times, the river's flow wouldn't be great enough to generate much electricity at all. The efficiency that results from the coordination is thought to generate an entire Bonneville Dam's worth of electricity. These agencies must plan carefully on multiple timelines -- annual, month-to-month, daily and hourly -- to make sure that the right amount of water is in the right places at the right times.
Not that there are, per se, right places and right times. The Corps, which sits at the apex of the group that runs the river and has ultimate authority when it comes to flood control, manages the river with many goals in mind: it must generate hydroelectricity, conserve fish, provide shipping channels and recreational areas and irrigate farmland. And all of those goals are directly opposed to flood control in the way that reservoirs are operated, calling for generally full reservoirs while flood control requires low reservoirs that are ever ready to receive runoff. Witt Anderson, the Corps' Northwestern Division director of programs, whose jurisdiction includes the Missouri River, points to that balance as a factor in last summer's Midwestern flooding.
Despite mountain snowpack that was 112% of average in April, the Corps waited until May, when mountain snowpack had risen to 135% of average, to adjust its dam release schedule on the Missouri and draw down its reservoirs to receive the extra water. Then extraordinary rainfall in the third week of May forced another adjustment. "60 million acre-feet [20 trillion gallons] of storage was overwhelmed by meteorological events," says Anderson. The political outrage that followed the flooding has focused largely on why the Corps didn't draw down its reservoirs earlier. Anderson's response points to the Corps' opposing responsibilities.
"From 2000 to 2007 we had a drought. Everyone was clamoring for more water in the reservoirs," he says of the Missouri system. "Now people say 'well, obviously, we're in a wet period now.' Sure, we'll check our farmers' almanac, but this really isn't so obvious -- the wet period could end at any time and we'll be left with too little water in the reservoirs. … During drought, people forgot about flooding conditions. Now, people are forgetting about drought."
The Columbia basin experienced near-record snowmelt last spring that nevertheless caused no major flooding. "This year's snowmelt was made to order," says Jim Barton, who oversees the Corps' reservoir management in the Columbia basin. "Now people say we've been too conservative."
The intricate planning process that tries to balance these demands begins at the National Weather Service's Northwest River Forecast Center. "I can never have too much data," says Harold H. Opitz, hydrologist-in-charge. His office digests data from 2,200 precipitation gauges and 1,800 river gauges maintained by both professionals (at airports) and enthusiasts (like high school science classes) to develop what it calls a "checkbook accounting" of precipitation that has fallen in the Columbia Basin: if an inch of water falls as snow high in the Rocky Mountains, forecasters figure it'll move down the river eventually -- the issue is when it will move down the river, and that's a question of some subtlety. Snowmelt can be hastened by rainstorms and slowed by layers of ice inside snowpack; the River Forecast Center needs to develop a thorough understanding of the water stored in the mountains every winter, and once it's come up with figures, they're in high demand. River flows in the West have enormous impact not only on electricity generation, but also on irrigation and fish passage. Barton says "we overload our phone capacity every time we have a conference call" because bankers join the line in such great numbers.
Once a day, the River Forecast Center compiles two streamflow forecasts -- a short-term outlook in six-hour increments and a longer-term 120-day forecast -- for 212 different points on rivers and streams throughout the Columbia basin. With a phone call, it hands them off to the Army Corps of Engineers. The Corps uses a sophisticated suite of statistical and physical models to arrive at reservoir levels that are most likely to keep the lights on and Portland dry.
The latest in this modeling software is called HEC-ResSim, developed at the Corps of Engineers' Hydrologic Engineering Center, a second-floor office above a group of storefronts. The software is helping to formalize and make more reliable the complex process of planning reservoir levels.
"To get started, I had to know something about hydropower, something about flood control, something about Native American fishing rights, something about treaty obligations," says George "Chan" Modini, the engineer who oversees ResSim. Modini is tall and square, with the precise bearing of a drafting tool. He started working for the Corps 24 years ago when he was 22, and before he took charge of ResSim he controlled the Willamette River in Oregon. "You used to have to take snowmelt forecasts, power requirements, fishery requirements, treaty requirements, encapsulate them in your head, run it annually, and do it fast enough so that you can share it and implement it," he says. "You used to sit around and hear these oral traditions. Now data is replacing our oral traditions."
ResSim, which has been under development for 15 years, simplifies the process of creating reservoir plans enormously and packs it all in an easy-to-use graphical interface. It stores streamflow data in a 70-year archive and lets engineers run "traces," or annual simulations, against historical patterns. Modini calls it a "multi decision-making model," that can take into account all of the Corps' objectives in operating the river. "Say it's January and you don't really know how the snowpack will be melting in May. You start with an assumption that you'll run the system in a certain way. Then you try out scenarios -- late runoff, lots of rain, warm temperatures. You can try out 50 different traces and look at which requirements are met." Considerations come down to the very specific -- say, avoid using a certain spillway gate at the McNary Dam because it's having mechanical problems, and the software's conclusions are specific as well, producing streamflow estimates at any of thousands of points in the basin being analyzed.
Future versions of ResSim should incorporate economic value considerations. "We want to be able to say, 'if water is this high, we'll see $6 billion worth of damage. If it's this high, we'll see $8 billion,'" says Anderson. "You can say, 'this is the property inundated under this scenario.' That's very powerful," says Barton.
After running its models, the Corps sends its reservoir plan back to the Northwest River Forecast Center, which develops a definitive streamflow forecast based on the Corps' plans. That might trigger another round of back-and-forth if the Weather Service thinks something might go awry.
At the end of the planning process, everyone has guidelines in hand for operating the river. Hour-to-hour, much of the river's operation falls to the Bonneville Power Administration, a Department of Energy agency that distributes power from the federal dams in the Northwest.
Daily electricity demand fluctuates enormously, so the river fluctuates with it, creating pulses of water that move from Grand Coulee down to the Pacific. Hydropower output on the BPA's network might be 4,000 megawatts at 4 o'clock in the morning, rise to 8,000 megawatts by 7 A.M., and reach 10,000 megawatts by noon. This is where hydropower's flexibility becomes important: thermal plants, like coal and nuclear installations, can take days to change output substantially. Since hydropower plants can ramp their production up or down in a matter of seconds, they're called upon to make nuanced shifts in output while coal and nuclear plants hum along at constant levels, providing baseload power.
The dams were built to be flexible in balancing out demand. Now, they're increasingly balancing out supply as well. The installation of 3,500 megawatts of wind capacity -- expected to rise to 6,000 megawatts by 2013 -- in Bonneville's territory has made load balancing more complex. Most of the wind capacity in the Northwest is concentrated in just a few locations along the Columbia River. When the wind blows there, they generate close to capacity; when the wind stops blowing, they generate close to nothing. And they can go from nothing to full output in as little as a couple of hours.
Renewable energy has reinvigorated the market for 'flexible dispatch' electricity that can be produced at a moment's notice, and hydropower is the biggest source of flexible dispatch available -- and is much cheaper to run than the natural-gas turbines that serve that market in other parts of the country. "Hydro is the silver bullet, and we didn't even know it," says Julien Dumoulin-Smith, an electric utilities analyst at UBS.
It's also brought about tension when the BPA hasn't been able to change its output. Both wind and hydro generation are subject to nature at the extremes. In May 2011, with near-record snowmelt swelling the Columbia River and spillways at their limits under environmental regulations, the BPA had to keep the Columbia's hydro turbines spinning. It told regional wind power producers to curtail their output by 6%. The producers howled, and in June the BPA ended up the subject of a complaint before the Federal Energy Regulatory Commission. At issue is what happens when too much electricity is on offer. The enormous supply of hydroelectricity during spring runoff can push electricity prices to zero -- the BPA gives away electricity to local utilities for free when it's forced to produce more than it wants to. Since wind producers enjoy production subsidies, they can push rates below zero, effectively paying other utilities to switch off their generators. Last winter, the BPA told wind producers under its balancing authority that it wouldn't pay negative rates to them during high-water events.
The BPA specifies output basepoints -- the round numbers that each dam should hit -- every hour. That's what Bob Neal was doing at 8:45 in the morning at the Duty Scheduling Center in Portland. And within those hourly basepoints, the BPA adjusts power output constantly: every two seconds, its office in Portland receives wind speed and electrical output data from every wind installation in its service area, and every two seconds it adjusts the turbines at its hydroelectric sources to compensate for changes in wind output. In a span of five minutes, total wind output in Bonneville's area can increase or decrease by as much as 200 megawatts -- equivalent to the total maximum output from three of Bonneville Dam's giant generators.
Climate change -- one of the factors that renewable energy is meant to address -- presents another possible confounding factor for the Columbia's managers. A University of Washington study suggested that the Columbia's cycle will shift forward so that snowmelt and its accompanying surge in river volume will happen a month earlier. On top of that, planners expect more rain during winter, which can cause problems for the river when it falls on snow, as well as drier and hotter summers, during which demand for electricity to power air conditioners will increase. That doesn't change day-to-day operations now, but over the next ten years, BPA intends to start taking climate change into account when it plans capital investments with decades-long lifespans.
That will add one more layer of shifting data -- a multi-year change in the river -- to the changes that it already encounters every month, day and second.
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