The Los Angeles Aqueduct is Wild

0:01 On the northern edge of Los Angeles,

0:04 fresh water spills down two stark concrete chutes

0:07 perched on the foothills of the San Gabriel Mountains,

0:10 a place simply called The Cascades.

0:13 It’s a deceptively simple-looking finish line:

0:15 the end of a roughly 300-mile (or 500 km) journey

0:20 from the eastern slopes of the Sierra Nevada into the city.

0:24 On November 5, 1913,

0:26 tens of thousands of people climbed these hills to watch the first water arrive.

0:31 When the gates finally opened, water trickled through,

0:35 but that trickle quickly became a torrent.

0:37 The project’s chief engineer, William Mulholland,

0:40 leaned over to the mayor and shouted the line

0:44 that’s been repeated ever since: “There it is, Mr.

0:47 Mayor.

0:47 Take it!” That moment was profound for a lot of reasons,

0:51 depending on where you live and how you feel about water rights.

0:55 LA didn’t become LA by living within the limits of its local resources.

0:59 Its meteoric growth into the metropolis we

1:03 know was enabled by an early and extraordinary

1:06 decision to reach far beyond its own watershed

1:10 and pull a whole new river into town.

1:13 Today, roughly a third of LA’s water comes

1:15 from the Eastern Sierra through the Los Angeles Aqueduct system.

1:19 That share swings with snowpack, drought, and environmental constraints,

1:24 but this one piece of infrastructure helped

1:27 turn a water-limited town into a world city.

1:30 It’s one of the most impressive

1:33 and controversial engineering projects in American history.

1:36 But to really appreciate that water in the cascades,

1:39 you have to look way upstream and see what it took to get it there.

1:46 It’s gravity, geology, politics,

1:47 and human ambition all in a part of the state that most people never see.

1:52 Let’s take a little tour so you can see what I mean.

1:56 I’m Grady and this is Practical Engineering.

2:08 When most people think about aqueducts, this is what they picture:

2:13 a bridge carrying water over a valley or river.

2:16 And, just to be clear, these are aqueducts.

2:19 But engineers often use the term more broadly to describe any type of conveyance

2:24 system that carries water over a long

2:27 distance from a source to a distribution point.

2:30 Could be a canal, a pipe, a tunnel, or even just a ditch.

2:35 In the case of the LA aqueduct, it’s all of them,

2:38 plus a lot of supporting infrastructure as well.

2:41 From the center of the city,

2:43 it’s about a four hour drive to the Owens River Diversion Weir.

2:47 It’s not accessible to the public,

2:49 but it is the official start of the LA Aqueduct,

2:52 at least when it was originally built.

2:54 Here, all the snowmelt and rain from a huge drainage system between

2:58 the Sierra Nevada and Inyo Mountains funnel down into the Owens River,

3:03 where a large concrete diversion weir peels nearly all

3:06 of it out of its natural course and into a canal.

3:10 This point is roughly 2,500 feet (or 750 meters) higher

3:14 in elevation than the bottom of the Cascades at the downstream end,

3:19 which makes it obvious why LA chose it as a source.

3:23 The entire aqueduct is a gravity machine.

3:26 There are no pumps pushing the water toward the city.

3:29 Half a mile of elevation change feels like a lot until

3:33 you realize you have to spread it out over 300 miles.

3:37 It’s all achieved through careful grading and managing

3:39 elevations along the way to keep the flow moving.

3:42 That care is particularly important in this upper section of the aqueduct,

3:47 where the water flows in an open canal.

3:50 To do this efficiently,

3:51 you need a relatively constant slope from start to finish.

3:54 That’s a tough thing to achieve on the surface of a bumpy earth.

3:59 Following a river valley makes this easier,

4:01 but you can see the twists and turns necessary

4:04 to keep the aqueduct on its gentle slope toward LA.

4:08 If it seems kind of wild that a city would buy

4:11 up the land and water rights from somewhere so far away,

4:14 it did to a lot of the people who lived in the Owens Valley, too.

4:18 A lot of the acquisitions and politics of the original

4:21 LA Aqueduct were carried out in bad faith,

4:25 souring relationships with landowners, ranchers,

4:27 farmers, and communities in the area.

4:30 The saga is full of broken promises and shady dealings.

4:34 Then when the diversion started, the area dried up,

4:38 disrupting the ecology of the region,

4:40 making agriculture more difficult and residents even more resentful.

4:46 Many resorted to violence, not against people but against the infrastructure.

4:50 They vandalized parts of the aqueduct,

4:53 a conflict that later became known as the California Water Wars.

4:57 In one case in 1924, ranchers used dynamite to blow up a part of the canal.

5:03 Later that year, they seized the Alabama Gates.

5:06 About 20 miles or 35 kilometers downstream from the diversion weir,

5:10 a set of gates sits on the eastern bank of the aqueduct canal.

5:14 Because it runs beside the river valley,

5:16 the aqueduct captures some of the water that flows down from the surrounding

5:20 mountains in addition to what’s diverted out of the Owens River,

5:24 particularly during strong storms.

5:26 That means it’s actually possible for the canal to overfill.

5:30 The Alabama Gates serve as a spillway,

5:33 allowing operators to divert water back down to the river.

5:37 This also helps drain the canal for maintenance or repairs when needed.

5:41 Those Owens Valley ranchers understood

5:43 exactly what the Alabama Gates controlled.

5:46 Open them, and the water would run back where it had always run,

5:50 down the Owens River, instead of south to Los Angeles.

5:54 The resistance simmered and flared for years,

5:56 but it didn’t end in the dramatic showdown at the aqueduct.

6:00 Instead, it ended at a bank counter.

6:02 The Inyo County Bank was run by two brothers who

6:06 were also key organizers and financiers of the resistance campaign.

6:10 In August 1927, an audit revealed major shortfalls and ongoing embezzlement,

6:17 and the bank quickly collapsed.

6:19 Residents across the valley saw their savings wiped out or frozen overnight,

6:24 shattering what was left of the community’s ability to keep fighting.

6:29 The Alabama Gates weren’t just a political flashpoint though.

6:32 They also marked an important dividing line in the aqueduct’s design.

6:36 LA knew that even if the ranchers didn’t

6:39 release the water to the river in protests,

6:42 a lot of it would end up there anyway through seepage.

6:45 As the canal climbed away from the valley floor and crossed more porous soil,

6:50 it would naturally lose its water through the ground.

6:53 So, at the Alabama Gates,

6:55 the aqueduct transitions from an unlined canal to a concrete-lined channel.

6:59 It’s still open to the air,

7:02 so there’s no protection against evaporation or contamination,

7:05 but the losses to the ground are a lot less.

7:09 This design continues for about 35 miles (or 55 kilometers) through the valley.

7:14 Along the way, the aqueduct passes the remains of Owens Lake.

7:19 Once a large body of water,

7:21 it quickly dried up with the diversion of the Owens River.

7:25 Of course, there were impacts to wildlife from the loss of water,

7:28 but the bigger problem came later: dust.

7:33 All the fine sediment that settled on the lakebed over

7:36 thousands of years was now exposed to the hot desert sun.

7:39 When the wind picked up,

7:41 it filled the air with fine particulates that are dangerous to breathe.

7:44 Over the years, there have been times when Owens Lake is

7:48 the single largest source of dust pollution in the entire country,

7:51 and LA has spent more than a billion

7:54 dollars just trying to fix this problem alone.

7:56 The aqueduct passing along the hillside past the lake

8:00 and its challenges is a reminder that the true cost of water is often a lot more

8:06 than the infrastructure it takes to deliver it.

8:08 So far, it might be obvious that this aqueduct system is pretty fragile

8:13 to be making up a major part of a city’s fresh water supply.

8:18 Even beyond the vandalism and political resistance,

8:21 there are a lot of things that could go wrong along the way,

8:24 from bank collapses, earthquakes, diversion failures, and more.

8:27 That’s why Haiwee Reservoir was originally built in a narrow

8:32 saddle between two hills as a kind of buffer.

8:35 With a dam on either side, it stored water up so the aqueduct

8:39 could keep running even during a disruption upstream.

8:42 It also slowed the water down,

8:45 exposing it to the hot desert sun as a natural form of UV disinfection.

8:50 In the 1960s, the reservoir was reconfigured

8:53 into two basins to add some flexibility.

8:56 That’s because, around that time, the LA aqueduct became two.

9:00 While the open-topped canal section was large enough to meet demands,

9:05 the underground conduit in the next section wasn’t.

9:08 So, LA built a second one in 1970 to increase the flow.

9:13 If you look at this map of the Haiwee Reservoirs,

9:16 you can see that water has two paths:

9:19 it can flow into the second aqueduct here from the north basin,

9:22 or it can pass through the Merritt Cut to the south reservoir,

9:27 through the intake there, and into the first aqueduct.

9:30 This setup allows for some redundancy,

9:33 along with regulation and balancing of the flows between the two aqueducts.

9:37 Haiwee marks the start of the long desert run,

9:40 with both systems no longer in open-topped lined canals,

9:45 but running underground in concrete conduits.

9:48 There are a lot of advantages to running

9:50 an aqueduct in a closed conduit underground,

9:53 especially one this long through a desert landscape.

9:56 There’s far less evaporation and less potential for contamination.

10:00 It doesn’t divide the landscape at the surface level,

10:03 so there’s no need for bridges, culverts, and wildlife crossings.

10:07 Going underground also offers more flexibility when it comes to topography.

10:12 You don’t have to follow the contours of the surface

10:15 so carefully because if you come to a hill,

10:18 you can just dig a little deeper to keep the constant slope.

10:21 Of course, those benefits come with a cost.

10:23 An underground conduit is more expensive than a simple channel on the surface,

10:28 and not all the problems with topography are solved.

10:31 This is Jawbone Canyon, one of the biggest drops for the first aqueduct.

10:39 Rather than taking a major detour around it,

10:43 the aqueduct descends 850 feet (or 250 meters) and then ascends back up.

10:49 This type of structure is often called an inverted siphon.

10:52 I’ve done a video on how these work for sewer systems,

10:55 and I’ve also done a video on flood tunnels that work in a similar way,

10:59 if you want to learn more after this.

11:02 Unlike the concrete conduit,

11:04 which really just acts like an underground canal with a roof,

11:08 this is one of the places where the water in the aqueduct is pressurized.

11:13 850 feet of water column is about 370 psi,

11:18 26 bar, or two-and-a-half Megapascals.

11:21 It’s a lot of pressure.

11:23 These sections of pipe had to be specially manufactured on the East Coast,

11:27 where the major steel facilities were,

11:30 and transported by ship because of their size.

11:33 They travelled all the way around Cape Horn,

11:36 since the Panama Canal was still under construction.

11:38 There are actually quite a few of these siphons

11:41 crossing canyons in this section of the aqueduct,

11:45 but Jawbone Canyon is the biggest one.

11:47 A little further downstream, the LA aqueduct crosses the California Aqueduct,

11:52 part of the State Water Project.

11:54 That system has a connection to LA as well,

11:57 but this branch at the crossing actually heads to Silverwood Lake.

12:02 However, there is a transfer facility, recently completed,

12:05 that can pump water out of the California

12:08 Aqueduct directly into the first LA aqueduct.

12:10 This creates opportunities for LA to buy water that moves through

12:15 the state system and offers some flexibility in where that water ends up.

12:20 There’s also a turn-in that can move water from the LA

12:24 aqueduct into the California aqueduct for situations where trades make sense.

12:27 The second LA aqueduct passes underneath the state canal here.

12:31 And this is a good example of the differences between the first

12:35 project (built in the 1910s) and the second one, built in the 1960s.

12:39 Over that time, the price of labor went

12:42 up a lot more than the price of materials.

12:45 Where the first one carefully followed the existing topography with bends

12:49 and turns to minimize the need for expensive pressurized pipe,

12:53 the second one could take a more direct path,

12:56 reducing labor in return for the more specialized conduit materials.

13:01 After wandering more than a hundred miles (or 160 kilometers) apart,

13:06 the two Los Angeles Aqueducts come back together at Fairmont Reservoir,

13:10 in the northern foothills of the Sierra Pelona Mountains.

13:13 This is the last major topographic barrier on the way to Los Angeles.

13:18 There was no way to go up and over without pumps,

13:21 so instead they went straight through.

13:24 The largest project was the Elizabeth tunnel.

13:27 Here, the two aqueducts come together again into a single watercourse.

13:31 About 5 miles or 8 kilometers of excavation

13:35 through everything from hard rock to loose,

13:38 wet ground became one of the most difficult parts of the entire project.

13:43 The tunnel required continuous temporary supports along most of its length,

13:48 followed by a permanent concrete lining.

13:50 It was a monumental effort for its time

13:53 and essential not only to cross the range.

13:56 The Elizabeth Tunnel also delivers that water under

13:59 pressure to the San Francisquito Power Plant Number 1.

14:03 This is the largest of the eight

14:06 hydroelectric plants that run along the aqueduct,

14:08 capturing some of the energy from the water as it flows downward toward LA.

14:13 These plants are a major part of how the project paid for itself,

14:17 and they continue to serve as an important

14:19 source of electricity in the region today.

14:21 Continuing downstream,

14:23 Bouquet Canyon reservoir adds another layer of operational flexibility.

14:28 It helps regulate flow through the power plants and provides additional storage,

14:33 a sort of insurance policy since this whole reach depends

14:36 on a single major tunnel crossing the San Andreas Fault.

14:40 In case of a major earthquake,

14:43 it’d be best if Angelinos could avoid a simultaneous water shortage.

14:48 The aqueduct splits again just upstream of the San Francisquito Plant Number 2,

14:53 which was famously destroyed by the St.

14:56 Francis Dam failure.

14:57 That reservoir project was designed to supplement

15:00 the storage capacity along the aqueduct,

15:03 but the dam failed catastrophically in 1928,

15:06 just 2 years after it was completed, killing more than 400 people and destroying

15:12 several parts of the aqueduct as well.

15:14 The tragedy was one of the worst engineering disasters in American history.

15:19 It put another stain on the aqueduct project,

15:22 and it effectively ruined the reputation of William Mulholland,

15:26 who was largely considered a hero in LA for all

15:29 his work on the aqueduct and the city’s water system.

15:33 The dam was never rebuilt,

15:35 but workers restored the aqueduct to functioning service in only 12 days.

15:40 At Drinkwater Reservoir,

15:41 the two aqueducts run roughly parallel through the Santa Clarita area,

15:47 sometimes aboveground and sometimes below,

15:49 before finally reaching the terminal structures that carry water into LA.

15:54 Usually, the water stays in the conduits,

15:56 which feed the two hydropower plants at the foot of the mountains.

16:00 If the plants are out of service or there’s more flow than they can handle,

16:05 you see excess water thundering through the cascade structures instead.

16:10 From here, the aqueduct drops out of the mountains

16:12 and into the north end of the San Fernando Valley,

16:15 where the water is treated and prepared for distribution.

16:19 After filtration and disinfection,

16:21 it’s stored in the Los Angeles Reservoir, the system’s terminal reservoir,

16:26 so the city can smooth out day-to-day swings

16:29 in demand even while the aqueduct’s inflow stays relatively steady.

16:33 For most of Los Angeles' history,

16:35 that “finished water storage” was out in the open air.

16:39 But in the 2000s, drinking-water rules pushed utilities to add

16:43 stronger protection for treated water held in uncovered reservoirs.

16:47 There’s a good chance you’ve seen

16:49 their solution on the Veritasium channel or elsewhere:

16:53 96 million plastic shade balls that act like a floating cover,

16:58 blocking sunlight to prevent water-chemistry

17:00 problems and helping keep wildlife out.

17:03 They’re the final protection for this water

17:06 that traveled so long to reach the city.

17:09 While the LA Reservoir is, in a sense, the end of the journey for this water,

17:14 the original diversion way back at Owen’s

17:17 River isn’t even technically the start anymore!

17:20 In 1940, LA extended the aqueduct

17:23 system upstream northward by connecting the Mono

17:27 basin and funneling its water through tunnels to the Owens River basin.

17:32 Like Owens Lake downstream, Mono Lake began drying out as well.

17:37 And also like Owens Lake, lawsuits, court orders,

17:40 and environmental regulations have tempered the value of this water source,

17:45 forcing LA to significantly reduce

17:48 diversions and implement costly restoration projects.

17:52 That’s kind of the story of the LA aqueduct in a nutshell.

17:55 The project seemed obvious from an engineering perspective.

17:58 There was lots of snowmelt in the mountains; the city had the technical prowess,

18:03 the funding, the elevation, and the political power to reach out and take it.

18:08 The result was one of the most impressive

18:12 works of infrastructure of the early 20th century.

18:15 And continued efforts to expand and improve

18:18 the system have made it even more efficient, flexible,

18:21 and valuable to the many millions of people who

18:24 live in one of the most populous cities in America,

18:27 delivering not only water but also hundreds of megawatts of hydropower.

18:32 But it many ways, it was not only unscrupulous, but also short-sighted.

18:37 Residents of the Owens Valley watched ranchland and farmland dry up

18:41 as the water that had shaped their home was rerouted south.

18:46 Native communities saw their homeland transformed

18:49 with access to gathering areas disrupted, places made unrecognizable,

18:54 and cultural ties strained by changes they didn’t choose.

18:58 Wind picked up alkaline dust from dried lakebeds.

19:02 Habitats were disrupted,

19:03 and the birds that depended on these waters and wetlands

19:07 lost part of what made this migration corridor work.

19:10 It’s easy to see why the aqueduct remains controversial,

19:14 and why what we sometimes dismiss as “red tape”

19:18 around major infrastructure is often completely justified due diligence.

19:23 As engineers, and really, as humans,

19:26 we have to try and account for costs that don’t show up on a balance sheet,

19:30 but can come back later as decades of lawsuits, mitigation, and restoration.

19:36 And even the aqueduct’s original thesis

19:39 (that there’s reliable snowmelt up there,

19:41 and a growing city down here) is starting to falter.

19:45 In recent decades, the mountains have

19:47 delivered less predictable runoff: more swings,

19:49 more years when the timing is wrong,

19:52 and more uncertainty about what “normal” even means anymore.

19:56 California’s climate has always moved in long cycles,

19:59 but the margin for error is thinner now,

20:02 and no one can say with much confidence when or if

20:05 the moisture the state depends on will return to its old pattern.

20:10 The hopeful part is that this is exactly where engineering makes a difference:

20:15 at the messy intersection of geology,

20:18 climate, culture, politics, and human need.

20:21 The Los Angeles Aqueduct is a case study

20:23 in what we can build when we’re ambitious, but also what happens when we treat

20:29 a landscape like a machine with only one output.

20:32 The next era of water engineers can learn a lot from it.

20:37 I mentioned the California Aqueduct as another

20:40 of the large systems that brings water to LA,

20:43 but there’s actually a third long-distance

20:45 aqueduct that delivers water to Angelinos,

20:48 this one coming all the way from Lake Havasu on the Colorado River.

20:52 Like the Owens River project, that one came with its own set of challenges,

20:57 controversy, and impressive feats of engineering.

21:00 My friend Sam from the Wendover Productions channel

21:02 talks about that, plus all the interplay between politics,

21:06 growth, drought, and engineering in his incredible documentary,

21:11 The Colorado Problem.

21:12 It’s basically an hour-and-a-half Wendover Productions

21:15 video with excellent graphics and interviews.

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