Tag: water

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Evaporation

When you read California’s daily water-storage reports and pore over the columns of data–for instance, from Lake Shasta, the state’s largest reservoir–you happen across this one: EVAP. It’s a record of how much water escapes the lake by changing state from liquid to gas. We’re schooled very early on in our science education about the hydrologic cycle. You know, the process by which water evaporates from oceans, lakes, rivers, and your scotch on the rocks, is transported into the atmosphere to fall as rain or snow, and then is evaporated and carried into the sky once more. Still, it’s one thing to know that a theoretical process is operating out there in the world somewhere and another to see its monumental workings in a statistical read-out.

Go back to Lake Shasta. I’ve been to the dam that holds it back, and I’ve driven past it dozens of times. It sprawls in an endless series of bays and inlets — old river courses — among the mountains that wall off the northern end of the Central Valley. The lake is usually ringed by a collar of brilliant orange-red soil, the upper margin of which marks the reservoir’s high-water mark. That ring is a sort of drought gauge: the more of it you see, the lower the lake is and, generally, the drier the state is.

One thing I don’t think when I drive past Shasta is that I’m watching a massive machine pumping millions of gallons of water into the sky. But that’s what it is. According to the summary from the Department of Water Resources California Data Exchange Center, yesterday the lake lost about 316 cubic feet of water per second through evaporation. Here’s what that is in household terms:

–A cubic foot of water is 7.48 gallons, so the lake was leaking 2,363.68 gallons into the atmosphere every second; three seconds’ worth at that rate would be more water than we’ve ever used in our Berkeley household in an entire month.

–Every minute, 141,820.8 gallons evaporated. In rough terms, the evaporation rate was 1 acre-foot every two minutes and 15 seconds. That’s a generous annual supply of water for two water-guzzling U.S. household.

–Every hour, 8,509,248 gallons of water — about 26.1 acre-feet — departed the lake. That’s enough to submerge a football field to a depth of 20 feet.

–For the day (and the evaporation rate is a 24-hour average), the lake lost 204,221,952 gallons, or 627 acre-feet. That’s a minor part of the reservoir’s net change for the day–the overall level fell by 7,271 acre-feet, mainly through water released for power generation–and it’s a tiny fraction of the lake’s current storage, about 3.15 million acre-feet.

Last stat for now: the process of evaporation is highly dependent on local weather, just like the grade-school lesson on the water cycle would suggest. When it’s warm, more water evaporates as the surface layer of lake water heats up. When it’s cool, the process slows. For the past month, the highest daily evaporation rate was 362 cubic feet per second, in the midst of a spike of very hot weather. The low point was 14 CFS, during a stretch of cool, rainy weather.

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Wind and Water

aqueduct040508.jpg

From the archives: Last spring, Kate and I drove out to Bethany Reservoir, just south of the Sacramento-San Joaquin Delta at one of the key points in the state’s complex water system. The site is also on the lower eastern slopes of the Altamont Pass country, a big wind-generation site. Pondering the state’s water story and how to tell it–do you take the narrative back to Genesis and/or The Big Bang and talk about where water itself comes from, and how long would it take from that point to get to a discussion of a salmon in the river?– I thought of that visit tonight. Here’s a shot of a wind farm virtually on the bank of the Delta-Mendota Canal–part of the federally developed Central Valley Project–just southeast of Bethany. Whatever you happen to think of the way the water systems were built here and the damage they have caused to salmon and other parts of the old California environment–the engineering is never less than impressive and sometimes beautiful.

The aqueducts move water through a combination of gentle flow and brute force: huge quantities of water are lifted from pumping stations to artificial lakes like Bethany. Then gravity takes over, and the water flows down the manmade rivers to the next set of pumps, maybe 60 or 100 miles away, and the process is repeated. (One of the more surreal sights in the state is along Interstate 5 as the highway climbs the Tehachapi Mountains. The aqueduct runs along the highway, and the water is pumped up nearly 2,000 feet through a pair of above-ground tunnels.) One beauty in the aqueducts is the way they follow the contours along the border of the Coast Range hills to the west and the great valley to the east. The engineers had to work with and respect the lay of the land here.

(Here’s the satellite view, with the hills in their full-on golden summer hue. The image shows Bethany Reservoir. The water comes in from a channel at the northwest corner, having been pumped out of the Sacramento River to a holding basin called Clifton Court Forebay. The California Aqueduct flows out to the south and east (below and to the right). Drag the map to follow the course of the aqueduct. In this image, the California Aqueduct is on the left and the Delta-Mendota Canal is to the right.)


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Watching Water

I’ve become preoccupied the last two or three months with the level of water in California’s reservoirs. If you’re inclined to, here’s where you can join in the fun: The state Department of Water Resources’ California Data Exchange Center. The cliche to describe a collection of information like this is “treasure trove.” For example, here’s one report that I’ve taken to taking a look at just about every morning: The Sacramento/San Joaquin Daily Reservoir Storage Summary. It’s a quick look at about three dozen state’s biggest storage facilities: how much water they’re holding, how many acre feet have flowed in or out in the past day, and–especially interesting–how much water they hold compared both to the average for this date and to the amount held a year ago.

There’s a story in the numbers, though I’m still puzzling out what it is. For instance, the state’s current drought is not a drought everywhere. Although rainfall and the mountain snowpack are generally below average, some reservoirs hold more than average for this time of year and much more than they did a year ago (which was an even worse year, precipitation-wise). But the numbers are just one dimension of a complicated picture. All that water has a lot of work to do. We count on it not just for irrigating the Central Valley farms and bringing drinking and lawn water to the citiies and suburbs, but for providing electricity, too. And in recent decades, the state and federal water managers have even been made conscious of another function the water might perform: preserving wildlife–especially the once-magnificent salmon runs in the Sacramento and San Joaquin watersheds.

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Water: The Midwest View

[Other posts on water: 

Big Bathtub II: 'Wasted']

Spotted the following letter today on the Chicago Tribune's (Tom Skillings's) weather page: 

Dear Tom,
The level of Lake Michigan is up 13 inches from last year. That's great, but could you 
express that in gallons of water?
Dan Fridley
Dear Dan,
The quantity of water that circulates through the Lake Michigan hydrologic system is 
truly staggering. And expressing that volume in units as miniscule as gallons yields 
numbers that are so huge as to be practically incomprehensible, but here it goes. 
A 13-inch increase in the level of Lake Michigan's 22,300 square miles amounts to 
5.044 trillion gallons of additional water (5,044,000,000,000 gallons). And that's not 
all. Lake Michigan and Lake Huron are essentially one lake; their water levels rise and 
fall in tandem. Thirteen inches of water added to the level of Lake Michigan means 13 
inches added to the 23,000 square miles of Lake Huron as well, and that amounts to an additional 5.202 trillion gallons (5,202,000,000,000 gallons).

So to summarize the arithmetic: Lakes Michigan and Huron, total surface area 45,300 square miles, have risen a foot and an inch in the past year. The total increase in water volume is 10.2 trillion gallons.

There is no doubt that is a lot of water. But it is an abstraction, proof that in the wet eastern two-thirds of the United States, water is, most of the time, something that's just there, like leaves on the trees, mosquitoes, corrupt politicians and bad beer. In fact, this immense amount of water, these trillions of gallons, are a trivial amount in the Great Lakes context, where volumes can be calculated in hundreds or thousands of cubic miles.

But before we get to that, let's put those 13 inches of Michigan/Huron water to work: let's frame them in the California context. 

In California and anywhere in the West where water means the difference between nothing and abundance, the working unit is the acre foot: the water it takes to submerge an acre a foot deep. An acre foot is 325,851 gallons, and that is said to be enough water for two average American households to keep their toilets flushed and lawns green for a year. 

The extra 13 inches of Michigan/Huron water: It comes out to something like 31.3 million acre feet. California's total reservoir capacity is said to be about 42 million acre feet. So that foot and an inch here–the incidental effect of increased runoff in their basins–would fill California's collection of monster lakes and catch basins three-quarters full. What a gift to a dry place. 

Lake Michigan has an approximate volume of 1,180 cubic miles, and Lake Huron 849. A cubic mile of water is just under 3.4 million acre feet. So the 13 extra inches of water in Michigan/Huron added about 9 cubic miles to their volume, or a little less than 0.5 percent (that's not too shabby, actually). All California's reservoir capacity would be satisfied with roughly 13 cubic miles, about 0.75 percent of the volume of the two lakes (and while we're throwing Great Lakes volume numbers around, the combined volume of Michigan, Huron, Erie and Ontario is about 2,538 cubic miles; the volume of Lake Superior is 2,900 cubic miles). 

When you see numbers like this, which may be close to meaningless without more context, you think you can understand the envy and ambition of Westerners who think the Great Lakes would solve all their problems. It seems a little crazy, until you travel up and down California and see how much has been invested in large-scale plumbing to make water go places and do things that seem to defy nature and physics.  

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Big Bathtub II: ‘Wasted’

The state periodically produces a document called the California Water Plan. It has been coming out in one form or other regularly or irregularly since 1930. It's part catalogue of the state's water resources, part status report on climate, rivers and the plumbing system that eases the thirst of farms and cities, and–as I read it–part marketing brochure for our biggest water customer, agriculture, and for new dams and reservoirs to secure its water supplies. That last aspect may seem odd, but I was struck by how the draft for the next water plan sings the praises of farmers' efficiency in using every last drop of water they get. It ought to be noted that California agriculture gets about four gallons out of five of the water impounded in the state's reservoirs.

The California Department of Water Resources offers a set of summary statistics on the state's natural water supply. In an average year, the state gets about 200 million acre feet of water in rain, snow, and river flows from other states (the latter is mostly by way of the Colorado River, long a major source of water for Southern California).

Of that 200 million acre feet–probably enough water to keep China going for a year if you could save every thimbleful–100 million or 120 million just sort of goes away. It evaporates, gets sucked up by redwood trees and crabgrass and some crops, or keeps natural marshes marshy. Of the remaining 80 million to 100 million acre feet, about half is captured for urban and agricultural uses. And the final portion, sometimes a quarter or more of all water that nature provides this dry place, flows down the great valley rivers, the Sacramento and San Joaquin, and out the coastal streams and bays to the Pacific. The state website describes this outflow as necessary "in part to meet environmental requirements." It sounds responsible of us. Almost altruistic.

If you've spent enough time in the San Francisco Bay region, you can name a couple of these "environmental requirements" almost without thinking about them. One is the need for an adequate flow of freshwater to prevent the "intrusion" of saltwater into the Sacramento-San Joaquin Delta. Brackish water threatens farms there, and it also effects residential users, some of whose water is siphoned right out of the Delta channels.

Another environmental factor is fish. The installation of the vast and complex system of dams, reservoirs, canals, pumps and siphons up and down the Central Valley–but especially in the Delta–has proved deadly for the great salmon runs that used to charge in from the Pacific nearly year round. Belatedly, state and federal water and wildlife officials, at the prompting and prodding of politicians, environmentalists and their lawyers, and judges, have seen fit to set aside some of the yearly flows for the good of the salmon and other imperiled species.

But that responsible, almost altruistic-sounding side of the state's water management sometimes lets its guard down. Our governor, remarkable for his knack to say the right thing–and for seeming to never dig in and deliver on that thing–was talking last week about all that must still be done to fix California. One of his pet projects is a $9 billion program of dam, reservoir, and canal construction. When he was making his pitch for it last week, he described the water that flows out to the Pacific as a waste. It's as if he and those of like mind believe that every glassful, every ounce, ought to be put to productive–you know, human–use.

In saying that, the governor gave voice to an old, old sentiment. Fish and wildlife were never a big consideration when the rivers got plumbed. Putting water to work was the chief concern.

In 1919–90 years ago this week, in fact–the California State Irrigation Association published a tract by Lt. Col. Robert Bradford Marshall. He was a veteran of the U.S. Geological Survey who had studied rivers in California and the West and the problem of getting water where it wasn't. His 12-page report was titled "Irrigation of Twelve Million Acres in the Valley of California." The Department of Water Resources acknowledges Marshall's report as the forebear of the present-day California Water Plan by listing it as the earliest iteration of the state's great water schemes. In short, Marshall proposed building a big dam in the northern Sacramento Valley and building a series of great canals to bring water to both farm and city. Thinking about our current governor and the idea that water that flows into the ocean without having done any honest work is a waste, I was struck by the tract's introduction to Marshall's ideas:

"… Back in those early days Col. Marshall wondered why they didn't irrigate in Northern California as they were doing in Colorado, where he had surveyed the year before. And he then as a young man dreamed that dream of EMPIRE BUILDING that every man of vision at one time or another has dreamed when he views California's millions of acres parched and burning in the summer and her millions of acre feet of water pouring into the Pacific in the winter. …"

And here's Marshall himself, describing that free-flowing water and the people who apparently refused to control it:

"The people of California, indifferent to the bountiful gifts that Nature has given them, sit idly by waiting for rain, indefinitely postponing irrigation, and allowing every year millions and millions of dollars in water to pour unused into the seas, when there are hungry thousands in this and in other countries pleading for food and when San Francisco and the Bay Cities, the metropolitan district of California, are begging for water."

In a dry year like this one, you still hear voices begging for water. And the answer we hear from the governor, farm interests, and water officials is now, as it was so long ago, to capture more of the water that falls on us and put it to work.

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Big Bathtub I: The Acre Foot

An acre foot is the amount of water it would take to flood an acre to a depth of one foot. An acre is, ballpark number only, a patch of land 100 feet by 400 feet. If you were standing on that patch of land with water about halfway up to your knees — well, you’d be having a direct experience of the acre foot.

An acre foot is 325,000 gallons. If you pay a water bill that shows how much you use, you can figure how long that much water would last you. The rule of thumb, that we journalists borrowed from “water experts” here in California was that an acre foot was enough to supply two average households for a year. That’s for use inside and outside the home for three or four people say, and it comes out to about 460 gallons a day for each household. Of course, there’s a lot of variation. An inner city apartment dweller uses a lot less than someone whose lawn looks like a fairway at Augusta National. Someone in a cool coastal area — Berkeley, for instance — uses less than someone in a much hotter area on the other side of the hills, lawn or no lawn.

The acre foot is a basic unit of life in California. Yes, weather people and water management officials count inches of rain and snow in the winter. But those units are incidental in a place that needs to capture and store an immense amount of water to irrigate roughly 15,000 square miles of crops and to supply 36 million people. The acre foot is the fundamental currency of reservoir storage and water delivery.

Up and down California, the federal government, the state government, electric utilities, county and city water companies, and irrigation districts have built reservoirs. They’re big bathtubs that together hold something like 42 million acre feet; that would be enough to submerge the entire state of Wisconsin under a foot of water. They reservoirs are expected to fill up in the winter and spring with runoff from the rains and melting snow running down from the Sierra Nevada. Then the water is pumped out during the dry season to help the fields and orchards thrive and to keep the showers and garden hoses flowing. Some water is even set aside for the fish that swim in dwindling numbers through the maze of waterways between reservoir, farm, and town.

A wet winter here–what people like to think of as normal, with nature’s tap switched on when we get into the middle of autumn–keeps our big bathtubs full and the water running where it’s needed. But there are other kinds of winters, too. Very wet ones, where the system simply can’t hold all the water coming down the rivers. And dry and very dry ones, where the water level in the reservoirs falls and keeps falling if two dry years come back to back.

We’re in what appears to be our third dry–or drier than “normal”–year in a row. Three of the biggest federal reservoirs in Northern California– Shasta, Oroville, and Folsom–all fell to critically low levels in December and January. Together, the three reservoirs can hold about 9 million acre feet; that’s about enough to supply a year’s worth of household water for New York, Pennsylvania, New Jersey, Massachusetts, Connecticut, Rhode Island, New Hampshire, Vermont, and Maine. That’s every U.S. resident east of the Great Lakes and north of the Mason-Dixon Line.

Remember,: that’s the capacity of just three reservoirs. There are dozens of others. During the last five weeks, copious rains have fallen and the water has started to rise in some of those big bathtubs. More about that later.

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Rain Chronicles

This will not be a banner precipitation season for California–though always keep your eye out for the neighbor building boats and inviting in pairs of every creature. But that doesn’t mean it is without interest. For starters, it could well be a significantly below-par year for rain and snow here, which would make it three such years in a row, and that’s never good news. Already this year, the probability of a third drought year is getting spun by the governor and his water people to bolster their campaign for more dams and fancy plumbing. You have to admire their pluck; with the state $40 billion in the hole just to buy things like bullets for the Highway Patrol, stun guns for prison guards, paper clips for the bureaucrats, and adult diapers for the Legislature, the guv and company are talking about getting the taxpayers to spring for another $10 billion or so.

Anyway. Talking rain at work today, someone produced a list that purports to show that a place called Blue Canyon, on Interstate 80 (and the Union Pacific) in the Sierra, is one of the 10 wettest locations in the Lower 48 states (and the wettest in California). It gets 68 inches of precipitation a year. No way, no how that is the wettest place in California. My money’s on Honeydew, a hamlet on the Mattole River in Humboldt County. With our neighbors, the Martinuccis, we actually drove through Honeydew once on our way up the coast. I have an impression of a general store and a narrow bridge. There’s some evidence–disappointingly scanty, to be honest, but it includes an official-looking listing of each state’s wettest location–that Honeydew regularly gets 100 inches plus of rain a year.

And leaving Honeydew out of the picture for a moment, there are at least half a dozen places up on the North Coast–towns like Fort Dick and Crescent City in Del Norte County–and further south–like Cazadero in Sonoma County–all average more than 70 inches a year.

Not that Blue Canyon doesn’t deserve attention. Some with the Weather Service credit it with being the snowiest recording station in the Lower 48 (averaging 240.8 inches a year). But here’s my favorite: in a table succinctly labeled “Mean Monthly and Annual Number of Hours with Measurable Precipitation, with Percent of Hours and Maximum 1-Hour Totals,” Blue Canyon is way out ahead of any California listing: On average, it’s precipitating there 10.6 percent of the hours in the year–928 hours and 30 minutes, roughly. Of course, that would make it just a run-of-the-mill place in much of Oregon and Washington (Portland’s percentage of precipitation hours per year: 10.9).

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Water, Water Everywhere

We’re in a drought here, or what they call a drought in California, so I’ve been thinking about water. Unfortunately, I’ve been thinking in terms that use lots of words and have led so far to dead ends. (Just a minute: a blog, dead ends–what’s the problem?) Anyway, for now, just a couple of numbers, from Shasta Lake, the biggest of the big network of reservoirs built to turn California’s mountains and rivers into a reliable water bank. In the past month at Shasta Dam, on the Sacramento River just north of the city of Redding:

–More than 20 inches of rain has fallen.

–The amount of water in the reservoir has increased by about one-third, from 1.41 million acre feet to 1.86 million acre feet.

–The amount of the increase over just a month, 450,000 acre feet, is about enough water to supply 2.2 million people for a year.

–But that’s not a lot in term of the demand for water here: About 80 to 85 percent of the “developed” water in California–water that’s impounded behind dams and delivered on demand to customers around the state–goes to farms. The rest goes to industry and residential users. The population of California is 36.5 million.

I’ve got lots more numbers kicking around, but that’s enough for now. In the next installment–soon!–I’ll try to make some sense of them.