An interlude.

Originally posted 2/5/7, 12:03am. Moved so the regulation posts could be continuous.

The cognoscenti call center pivot irrigation systems “circular moves”, in contrast to “linear moves”, in which an overhead sprinkler pipe spans the width of the field and rolls straight the length of the field. I was talking to this guy Vince one time, and when I mentioned circular moves, he narrowed his eyes at me and asked me if the word “moves” was indeed a noun in that sentence. I had to admit that it was. Vince was also the only person to give me a good explanation for the song lyrics “And I miss yoooouuuuuu, like the deserts miss the rain.” I’d never thought much about the song, until my sister mentioned that she hated it. “Deserts don’t miss the rain,” she said. “Deserts hate the rain. When deserts get rain, they stop being deserts.” When I told Vince these objections, he suggested that the deserts and rain were missing each other in the sense of passing each other without intersecting paths. He did hand gestures to illustrate.

You don’t see a lot of circular moves in California because circular moves have a fixed delivery rate, and that rate is too fast for our soil intake rates. Circular moves have to cover the whole circle before the soil dries out at the starting point. Every point on the circle will need some amount of water to meet evapotranspiration, say 4-5 inches in the summer. The circular move can put that amount of water out as it passes overhead, but on California soils a lot of that will run off. Some will infiltrate, but not enough to support a crop. If you have a center pivot irrigation system and see your crop wilting, the counterintuitive solution is to slow your circular move. It’ll hurt, because you’ll want to rush your sprinklers over the whole field. But that means that every spot will get not enough water. Slow your sprinkler to match the soil intake rate, and put enough down on most of the circle. Abandon some quadrant; you can rush your sprinklers over that to get back to the portion you can save.

Circular moves are rumored to be wicked hard to design. You want to save weight, so you shrink the pipes as they move outward. It is hard to size the sprinkler nozzles so that sprinklers close to the inside deliver the same amount of water as sprinklers close to the outside, which are traveling at a different speed and are on a different size pipe with different pressures. A4 asked whether the water pressure itself drives the circular move. They used to, but if you have to pressurize the water, you are better off just having motors on the pivot and peripheral wheel, ‘cause of the friction losses down the length of the arm. When I was doing irrigation system evaluations, I did one on an olive orchard right below Shasta Dam. He said he has pressure regulating valves on his main, ‘cause his water gets delivered to him with 90 feet of head. But that is exceptional.

Just doing my duty.

My background in water engineering was man-made irrigation structures, not built and natural flood systems. I'm not in the Flood Management Division, but you can imagine that the whole department is pretty focused on floods these days. We talk about them a lot right now, so I'm just learning stuff that any real fluvial geomorphologist (so hot!) would already know.

The coolest thing I learned recently is that the entire bed of a river drops during a flood event. Of course we knew that the top water level rises, but sediment in the channel bottom is picked up as well. A sandy river bottom can drop by fifteen to twenty feet, and be restored to close to its original profile as high flows recede.

I also learned that most of the flood water in the Sacramento Valley is carried in bypasses. The mainstem only holds about twenty percent of flood waters, which still looks pretty dramatic when it is lapping at the bridge at M St.

This morning I went over to the Joint Operations Center* to get trained in flood response. The training isn't coming any too soon, seeing as how I am working all tonight and tomorrow night. I'll be in the operations section, so I guess my job is to choose and coordinate responses to breaches in the system, and, you know, to save your life!

If something goes wrong, saving your life will involve a flurry of activity, and decisions based on not enough information, and maps and paper everywhere. But things are more likely to go right, so saving your life will probably mean sitting in a cold building with half a dozen other people and nothing to do at three in the morning. I'll have books and Internets but no email, so if you have suggestions for interesting sites with enough content to keep me awake, that would be great.


*Flood fighters like me just call it the JOC.

I'll save you!

When I got hired by the state, I didn't realize that stateworkers are considered emergency personnel and are required to respond to disasters. Of course I thought that was totally cool and wanted to be a firefighter, fighting forest fires with the heavy protective pants and a pulaski over my shoulder, but for some reason, just suspenders over a clingy black tank top that shows my sweaty, rippling triceps.

Round here though, we get called out for floods. The emergency response training happens in the fall, and I didn't get trained last fall, so I figured I missed my chance for this season. (I am told there is a daylong course in sandbags. Sweet.) But my boss just told me to call over to the Joint Operations Center; the department is "mobilizing personnel" against the possibility of a flood in the San Joaquin Valley this Sunday. The San Joaquin River is at capacity and reservoirs are dumping water as fast as they can to get ready for a weekend of rain.

I didn't get the training in hanging off rope ladders from helicopters to pull babies from a ferocious torrent, so it is more likely that I will be answering phones at the Batcave. Still, since I am an engineer, there is some slight chance I might be out surveying levees. Hope so.

CALFED spent a billion dollars.

This article about a student design contest focused on the Delta came over the water news about a week ago. I thought the winning idea - that the Delta become a national park, with historic towns, biking trails, observation posts and eco-housing – sounded like a nice place to visit. Except that even if the federal government weren’t trying to sell the lands they already hold, and even if the national government could manage the Delta better than the local government an hour’s drive away, why the hell would the state of California want to cede control over the linchpin of its water infrastructure to anyone?

So I was already shaking my head at the annoying graduate students when I got to this quote from one of the prizewinners:

“Nobody in California understands how important the Delta is for California or the United States.”

I would like to reassure her that there are people in California who do understand how important the Delta is. I know of people who have worked professionally on Delta issues for longer than she has been alive! Some of those people have even become important! It would be an exaggeration to say that my very own state agency does nothing but focus on the Bay-Delta, but it would not be an exaggeration to say that about this state agency! My agency has been known to spare a thought for the Delta too. Why, we have an office dedicated to the Delta! And we publish this, which I bet she used in her project! And we talk about it all the fucking time!

Look, I remember being an annoying graduate student and an insufferable undergraduate. I myself have been misquoted in newspaper articles. But I think that what she really meant to say was “I had never heard of the Delta until I did this project.” Which is totally legit. I only know it because it is my field, and I know precious little about landscape architecture. Still, I think I would stop myself before telling a newspaper reporter that nobody in California understands the importance of sprawl.

A fine quote from today's water news.

FISHING BANS: Salmon Fishing Ban Considered; Dwindling runs on the Klamath prompt a proposal to put 700 miles of coast off limits - Los Angeles Times – 3/4/06 - Eric Bailey, staff writer

[text omitted]

Commercial fishermen heaped blame Friday on the Bush administration for managing the river in a way they contend favors farmers, dam operators and timber companies at the expense of fish.

"The federal government has done absolutely nothing to help, and fishermen are angry," said Zeke Grader, executive director of the Pacific Coast Federation of Fishermen's Assns. "It's almost like they created this Klamath situation to make them look competent on Katrina."

[text omitted]