Tag: water statistics

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California Water: Is the Drought Over?

Is California’s drought over? OK, let me take a step back. Yes, I realize one could debate whether the last three years in California actually constitute a drought. But that’s a discussion for another time. For now, I think everyone can agree that we’ve had lower-than-average precipitation for the past three years.

The only reason to ask the question is that, after the first half of the wet season delivered only spotty rain, we’ve had a pretty solid week of downpours. Water is sluicing into our reservoirs, and the hills are greening up. All of that is a sign of what we think winter should be here. ( My favorite water statistic of the week: when the storms were at their heaviest around Lake Shasta, California’s biggest reservoir, water was flowing into the lake at about 500,000 gallons per second. That’s 1.5 acre feet, or about enough for three “average” households for a year, every second.*)

Amazing numbers like that aside, the people who get paid to think about whether the drought is over say “not yet.” The San Jose Mercury News published a good summary of the situation a couple days ago: “It’s soaking. But the drought’s not over just yet.”

That story does contain one bit of typically odd California thinking about rain and water, though. It quotes a very knowledgeable local meteorologist, Jan Null, about where we stand in terms of normal rainfall. He says: “”We need February and March to be wetter than January to really end the drought. You have to look at the long game here. This is a great start, but we need to keep it going.”

The last sentence stopped me: “This is a great start, but we need to keep it going.”

Of course, Mr. Null recognizes better than most that the amount of rain we get and when we get it is out of anyone’s control. Still, “we’ve got to keep it going.” Maybe he’s a professional rainmaker.

Once you understand the importance of water in California, once you get how crucial the winter rains are, there’s a score-keeping aspect to weather-watching here. It becomes second nature to study the rain gauge and the seasonal precipitation table as an index of performance, a reflection on whether a great collective goal is being attained. Lots of rain means we’re doing well (and that we can put the complexities of water supply out of our minds). A dry spell means we’re failing (and that there will be hell to pay, or at least the strong possibility of stringent conservation measures).

But in reality, there’s no performance going on. The rain is the rain, and the climate is the climate. California’s rainfall is famously variable. Dry spells can be counted on, and the current run of dry years is the third we’ve had since I arrived in Berkeley in the ’70s. My first California winter, 1976-’77, was bone dry and was in fact the second year of the driest two-year period ever recorded here. A decade later, from roughly 1986 through 1992, we had another run of dry years. And if our winter rains were to stop now, we’d be in the fourth year of drier-than-normal years. In between these periods we’ve had average years and very wet years and years that didn’t quite hit the average. That might not be too different from anywhere else. The reason it’s a bigger deal here than it might be in, say, central Wisconsin, is that we have a six-month dry season, we need to store water to get through that, and we have 37 million people and millions and millions acres of farmland that need water whether it’s falling from the sky or not. Thus the need to believe we can wish the rain to keep going during the wet season and the tendency to feel disappointment when the winter turns into a string of dry, sunny days.

*500,000 gallons per second. Here’s the arithmetic: California Department of Water Resources figures (here: http://bit.ly/6HzIuu) show that in the hour between noon and 1 p.m. on Tuesday, January 19, the net inflow into the lake was 66,288 cubic feet per second. That’s the highest inflow figure for any single hour all week. One cubic foot equals 7.48 gallons. 66,288*7.48=495,834.24 gallons. One acre foot=325,851 gallons. And 495,834.24/325,851=1.52 acre feet. Per second. For the entire 24 hours of the 19th, Lake Shasta’s inflow averaged just over 1 acre foot a second.

Bonus feature! KQED’s latest California Reservoir Watch map, updated earlier today:


View KQED: California Reservoir Watch in a larger map

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Water Project: California Reservoir Watch

The background: The state Department of Water Resources announced yesterday that its “initial allocation” of supplies for the next year is 5 percent. What that means: It’s only promising to deliver 5 percent of the water that customers have asked for. The reason: Three low-rainfall years–nothing Mother Nature can’t handle, but a disaster for us humans–and some limits placed on water shipments to protect endangered fish. The reaction: Agriculture and other water contractors say it sure looks like the sky is falling. So does the governor, whose biggest agenda item for his last year in office is getting the voters to pass an $11 billion bond for water projects. The rhetoric from the water interests has led some environmentalists and other water-policy skeptics to say the 5 percent allocation is little more than a scare tactic to sell the bond.

Whatever the case may be, I noticed an interesting thing in the documents the Department of Water Resources released with its allocation announcement: The water managers are cutting the promised deliveries to 5 percent even though a chart (PDF) they put out shows they have 20 percent more water in the bank than they did last year–when the initial allocation was 15 percent. One of my colleagues at KQED asked the department’s deputy director about this, and the initial answer was along the lines of, “That’s weird–I don’t know.” Later, she suggested the chart was wrong because it didn’t take into account the fact some of the water in storage is already committed to other customers and can’t be allocated. (As a matter of fact, current combined storage at major reservoirs in the Sacramento-San Joaquin system is running 17 percent ahead of last year at this time; of course, last year was really, really bad, and that same group of reservoirs is only storing 72 percent of average for this date.)

The chart still hasn’t been fixed, though, and it lends credence to the arguments that the allocation–which is only a beginning number and is likely to be adjusted far upward as the season progresses–is being used to aid the bond campaign.

Anyway; Since I got into all this stuff yesterday, and since reservoir levels are such a big part of this debate and the state’s well-being, I put together a map showing where the biggest reservoirs are and the current storage levels. Here it is:


View KQED: California Reservoir Watch in a larger map

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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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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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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.