Putting the life back in science fiction


Water, salt, sediment, and power. And the future

Well, I finally finished reading Mark Reisner’s Cadillac Desert (Amazon link), and I highly recommend it, if you haven’t read it already, even though the original text was written in the 1980s.  For those who haven’t read it, the thumbnail is that it’s a muckraking history of water works in the US, primarily in the western US in the 20th Century.  The reason I strongly recommend it is not just for what Reisner got right (or apparently got right), but also what he got wrong, like his prediction of the huge water crisis of 2000.

I’m not going to do a book review here.  Rather, I’m going to talk about some of the things I got out of it, including how hard it is to predict when water crises will hit.

Here’s the basic way Reisner learned to think of rivers.  On the upstream end, water falls out of the sky or comes out of the ground.  Since water’s kind of a universal solvent, it inevitably causes both erosion and dissolution.  As a result, rivers have a load of dissolved minerals–salts, to oversimplify–and a load of suspended solids, which become sediments when the river lacks the energy to keep them suspended.  At flood stage, those suspended solids can be house-sized boulders.  In still water, even clay particles eventually settle out.  Normally riverine energies are somewhere in between.

In the normal course of things, a river system either empties into the ocean, or into an inland lake like the Great Salt Lake.  There, the sediments and salts build up as the water evaporates.  In the western US, the great salt flats are the remnants of lakes that dried up completely, while the ocean is salty due to all the salts washing into it from the rivers and streams.  In geologic time, the salts can be entombed in sediments, moved onto continents by tectonics, and so the ocean doesn’t become a huge salt flat, but you get the idea.

Also in the normal course of things, rivers irrigate riparian vegetation by flooding.  This scours out the old sediments (which can contain salts due to summer evaporation) and lays down new sediments.  This is the way the Nile used to work, and fresh river sediments can be extremely fertile.  Tohono O’odham farmers reportedly like to farm following flash floods, for exactly this reason.

Now, let’s add some dams and irrigation canals to all this. Neither are new technologies, and they are problematic.

Here’s the first problem: when you dam a river, the sediment it carried to that point drops out behind the dam, as the stream loses energy in the reservoir. Those sediments fill up the reservoir, and it takes a lot of work to get the sediments out, and then you have to figure out where to put them so that they don’t wash right back into the river and silt up the reservoir again.  Ultimately, the reservoir will silt up to the point of uselessness, and pulling sediments out is designed to prolong its useful lifespan, not to make it immortal.

And there’s a second problem: as water evaporates from the reservoir, the salt concentration in the remaining water increases.  When you pull that water out to irrigate fields, evaporation, plus transpiration from the plants, pulls out still more water, leaving the salts behind in the soil.  How fast this happens depends on how careless you are.  To some extent, you can flush out more salty water with less salty water by irrigating more, but then that salty water has to go somewhere.  Ideally it should go into the ocean.  More often, it goes into someone’s field downstream, or into a place like the Salton Sea, which act(ed) as the sump for the Imperial Valley’s efforts to use salty water from the Colorado to wash salts out of their fields.  Still, over time, irrigated fields salt up.  This limits the crops you can grow on them, and in droughts, the salt problems get worse as water becomes less available to flush them out.  According to Reisner, the only place that successfully was irrigated for thousands of years was the Nile Delta, and that was because the Nile River flushed the fields most years.  Once the Aswan Dam was installed, they started having the same silt and salt problems that everyone else does.  While I’m not sure he’s right for the entire world (looking at the Yellow River and Tonle Sap), I think he’s correct for arid regions.

There’s actually a third problem, too: rivers aren’t just irrigation water wasting into the ocean, they’re living systems whose life is exploitable too.  All those dams harm any downstream fisheries, as well as the passage of anadromous fish like salmon and steelhead.  The loss of the Nile has led to the ecological death of the Nile Delta, along with some very long-term fisheries that went away when the sediments were caught behind the Aswan Dam, rather than flushed down the Nile every year.

Now with all these problems, why dam?  The answer is two-fold.  First, to people adopting irrigated agriculture for the first time, the problems aren’t that obvious, while turning the desert into a paradise through hard work and faith (I’ll come back to this) is quite obvious.  The second part is that, once you make millions of people and billions of dollars dependent on such systems, they’ll just have to be maintained in spite of the problems and cost.  Right?

Faith.  According to Reisner, the first anglos to do serious irrigated agriculture in the west were the Mormons, who pioneered digging ditches starting in Utah and then throughout the region (even as far as Riverside, CA, although they later retrenched in Utah).  Their hard work diverting the streams flowing into the Great Salt Lake made many people think that it was possible to turn the desert into farmland, and the land-rush was on.  For the non-Mormons, it was faith in science and engineering, from the debunked theory that “rain follows the plow” to the faith in the prowess of the Bureau of Reclamation and Army Corps of Engineers, that led them to continue moving to the Southwest and trying their hand at irrigating the deserts.

There’s also a large element of political power involved, because especially after WWII, eastern farmers were getting paid to not plant crops when prices were low, while western farmers received massively subsidized water to plant those same crops.  That’s how California and Arizona cotton could compete with cotton from Alabama and Mississippi, for example.

The men running the relevant congressional committees were westerners, and the example of the New Deal had made the politicians think that, so long as the economy grew, they could make dams and other waterworks with abandon, help their constituents, and push the costs off onto the future when growth would cover them, as it had covered Hoover Dam when it was built in the depths of the Depression.   Reisner calls water projects “wampum” for congressmen all over the US, and planting a water project in someone’s district was a standard way to pay for a political favor elsewhere.  This was a big element of the pork barrel politics that inflated our national debt to the levels we see to day.  To a large extent, that debt is welfare money, but it’s welfare for western farmers and ranchers (many of them now industrial farms owned by multinationals), not for poor, inner city minorities.  There’s a deep irony that so many small government rural Republicans would become dispossessed migrants if the government stopped subsidizing their way of life, but that’s what we’ve got in the US.

It’s even worse with the southwestern cities.  LA gets a lot of water pumped uphill from the Sacramento Delta and over the Tehachapi Mountains, in part because the late Gov. Pat Brown (Jerry Brown’s father) thought that he’d rather see all the development messing up southern California, rather than up in his native northern California, and he got some interesting political deals to make it “pay” for all the players involved, including the oil companies.  I could go on, but the political chicanery and very human personalities of the people involved are the best part of Reisner’s book.

Yes, our western water system is unsustainable.  Eventually, the Oglalla Aquifer under the Dust Bowl will run dry, the area will perforce switch back to grazing and dryland farming, and there likely will be another Dust Bowl.  Yes, the loss of western agriculture means that a lot of cheap food that has been feeding the world and keeping it “peaceful” will disappear, world food prices will go up (China, Russia, and Australia have areas with the same problems as the American West), and that will cause or exacerbate famine and civil unrest all over the globe.

One thing that’s not clear is when all the bad things start happening.  Reisner figured it would happen by 2000, but he’s demonstrably wrong by now.   He thought that San Joaquin groundwater would be exhausted by now, even though others thought it would be exhausted decades before, and so far everyone’s been wrong.  Partly they keep finding more groundwater, partly they keep getting more water pumped south, and partly the land’s getting too salty for many crops, so that less is getting pumped.  Gov. Jerry Brown is still trying to complete his father’s Peripheral Canal (it has a different name now), and so forth.

The reason the whole thing hasn’t yet crashed is that when there are tens of millions of people depending on a project, no politician will cut them off, especially in the name of something as ill-defined as long-term sustainability.  The pols will find a way to patch things together, even if the cost is passed onto the future.  The West’s water systems are, for the most part, rationally designed on the individual level, but the designs and locations are based on fundamentally insane and short-sighted, even stupid, politics.  According to Reisner,  all the best sites for dams were dammed by the 1940s, and the western dams proposed now (many are designs 50 years old) are stupid places to dams.  Worse, the projects were designed to last 50-100 years, they were all built at least 50 years ago, and now they’re going to be maintained and upgraded well beyond their design life, except in cases where they’re so stupid that it’s better to take them apart, as we’re seeing with dam removal projects.

Still, the upshot is that it’s even harder than I thought to predict when our water system will fall apart.  The key factor isn’t design life, it’s maintenance, political will, and economic growth.  We’re willing to pay for maintenance so long as we can convince ourselves that future growth will cover the costs.  When the growth really and truly stops, the whole thing will start to fall apart, but I don’t think we’ll be able to see that coming more than a few years in advance.

The “good” news is that, if we can find ways to keep PV solar panels clean without using water (as they do with the Mars Rovers), we can increasingly grow solar farms in old irrigated fields.  In the decades to come, the West may become an exporter of power rather than food, with the cities as manufacturing hubs and food imported from elsewhere.  It’s not a great solution, and I suspect that a lot of people will leave the West, but it’s what we’ve got.

The flip side to that is that where the solar and wind plants go is a matter of politics as much as rational economics.  We saw that with Ivanpah, and we’ll see it many more times.  Just as some of the old dams were irrational designs that delivered, at best, ten cents on every dollar invested, but were built anyway, I suspect we’ll see a huge proliferation of solar and wind farms that don’t make a lot of sense economically, but which bring home the bacon to some politician or other.

What did I miss?

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7 Comments so far
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The salt build up is a problem of irrigation in areas of low rainfall and high evaporation. One way we could mitigate is to remove dissolved salts in the reservoir water. very expensive to be sure, but solar evaporators might be the best way to go.

Sediment is always a problem, whether behind dams or in harbors.All we can do is move it or ve a bit more clever in preventing build up.

Here in the central Valley, the aquifer is dropping very rapidly and drilling to deepen wells is frenzied. Apparently it is hard to get new equipment so the work backup just gets worse. Some towns at the southern end of teh valley have gone dry and need water shipped in. So for them, the crisis has arrived.

Longer term, rich coastal cities can desalinate water, an option unavailable for inland cities. Farms will have to find a way to recycle water, but this is a huge political issue as you know. It may require a drastic change in water rights to reallocate water away from farms that use most of the water in California to uses that are more valuable.

Household water recycling is an almost untapped water resource and this could be stimulated with incentives, just as the state incentivizes lawn removal to reduce water use.

Comment by Alex Tolley

I’m a fan of desalination. Never understood why there’s political will to pipeline oil/NG but not water. And it’s no secret that sea water levels are rising, so plenty of water available.

Sorta related … Recently visited a friend who lives next to a conservation marsh/wetlands area. Quite a few restrictions re: land use mostly to maintain the ‘wet’ for the existing native flora and fauna. But I wonder/ask how is it possible to keep the wetland ‘wet’ in perpetuity when the normal evolution of such lands is that eventually marsh becomes wetland, wetland becomes meadow, etc.

Comment by SFreader

Probably worth reading this article, then: http://www.voiceofsandiego.org/topics/science-environment/desalination-plant-faces-environmental-questions/

The tl;dr version is that things are always more expensive than they first appear. The rather eye-opening number in the number is the 2.55 megawatt-hours per year needed to supply an average San Diegan household’s worth of drinking water through desalination, when an San Diegan average household uses 6 megawatt-hours per year right now. I suppose you could balance it out by outlawing all lawns, but going to 100% desalination for drinking water will be energetically expensive, as well as financially expensive.

Comment by Heteromeles

The problem is the vast scale. Water use dwarfs oil use. If you could repurpose all the USA’s oil transportation infrastructure for fresh water, it wouldn’t come close to covering California’s water deficit.

In a near-past or near-future drought year, California has a water deficit of about 6 million acre-feet (7.4 * 10^12 liters). The billion dollar Carlsbad desalination plant that opened late last year can supply one part out of 107 of that deficit. The plant draws 38 megawatts of power on average. If you wanted to desalinate to meet the entire near-future water deficit, you’d be spending on the order of $100 billion in construction costs and adding 4066 megawatts to California’s base load electricity consumption. For comparison, all of California’s non-hydro renewable sources together produced 4559 MW (average) in 2015. At current industrial customer electricity rates it’s $3.7 billion per year just for the power. If California committed to building such a huge desalination fleet the costs would probably fall with experience, but I don’t think they’ll fall enough to be cheap on an absolute scale.

The second elephant in the room is that the 6 million acre foot deficit is just the start. Climate change and population growth are going to make it worse. There’s a pretty good case for a 25 million acre foot deficit in the foreseeable future, based on population and climate changes: https://mogreenstats.com/2015/07/09/drought-in-california-part-3-californias-total-water-deficit/

Water diversion on this scale from natural sources is possible if cost is no object, protesting landowners and environmentalists can just be thrown in prison, and you have a one party dictatorship running the country. See China’s South–North Water Transfer Project. Note the enormous price tag even though it’s built with Chinese labor and equipment on Chinese territory.

At the same time, forage crops (cow food) are consuming 10 million acre feet of water per year in California. No sane government would help farmers turn gold into lead by e.g. growing alfalfa with desalinated water. The Carlsbad desalination plant sells water for over $2000 per acre-foot while alfalfa brings in about $175 per acre-foot of water consumed.

Comment by Matt

The smartest approach is water conservation. Using less, reusing what you have. After that, desalinate. US use is about 2x EU use per capita. In California we saved a huge fraction of residential water by careful use and not watering lawns. The problem is agriculture that is still very wasteful with water because it is so cheap. Large, wealthy farms just dig expensive deep wells to the aquifers. After pumping the water is used as it always has been. That needs to be the target for water conservation. Water taxes might be a good Pigou tax to change farming behavior.

Comment by atolley1954

“The good news is that, if we can find ways to keep PV solar panels clean without using water (as they do with the Mars Rovers), we can increasingly grow solar farms in old irrigated fields. In the decades to come, the West may become an exporter of power rather than food, with the cities as manufacturing hubs and food imported from elsewhere.”

There’s at least one manufacturer already making water-free automatic solar cleaning systems on a large scale, Ecoppia. Even automatic cleaners that still use water (like SunPower’s Oasis system) use much less than hand-cleaning solar modules with water, which in turn uses much less than actually irrigating the land for growing crops.

This report on solar water consumption, using numbers from 2010, indicates a maximum of ~5.7 acre-feet of water use per megawatt-peak during constructing a large PV facility and 0.053 acre-feet consumed per year per megawatt-peak for O&M cleaning: http://energy.sandia.gov/wp-content/gallery/uploads/SAND2013_5238.pdf

That’s for manual cleaning with water. Even for manual cleaning the numbers would be lower today because system efficiencies are higher, meaning less area requires cleaning and dust control per megawatt of modules. Taking the largest values estimated in 2010 we’re talking about a total amortized water consumption of 0.23 acre-feet per megawatt-peak over a 25 year facility life. At 25% capacity factor that’s 0.0000042 acre-feet per megawatt hour of electricity actually generated. If the electricity wholesales for $60 per megawatt hour that’s $14,000,000 from one acre-foot of water consumed, compared with $175 for alfalfa.

I expect California to remain an agricultural powerhouse for the rest of this century because of historical path dependency and network effects (though I expect we’ll also see a lot more solar power on degraded land). I don’t expect it to remain a powerhouse of dairy and cow-food production though, for the reasons given in my other post and above. It’ll have to be crops that are directly consumed by human beings and thereby produce more people-food per unit of water consumed. I could see systems like those developed by Sundrop Farms (http://www.sundropfarms.com/) generating a lot of produce even if California becomes as parched as South Australia.

Comment by Matt

[…] have in the US (source). In my blog, I recently posted about some of the other problems dams have (link). The tl;dr version is that dams have serious issues with sediments and salt, the 50-100 year […]

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