Lesson video

Hello, geographers.

My name is Mrs. Griffiths.

Welcome to today's lesson about water strategies to increase supply.

So we're gonna be thinking about what we can do to increase water resources on a large scale and focus in on a real-world example in California.

Shall we get started? Our outcome for today is I can describe different strategies used to increase water supply and outline the advantages and disadvantages of California's water project.

So that's what I hope you can say by the end of the lesson.

We have two keywords or key terms for us to try and remember the definition of today.

One is water transfer.

The movement of water through pipes or along rivers from areas of water surplus to areas of water deficit.

Also desalination.

The industrial conversion of salt water into fresh water, commonly in arid or semi-arid areas.

So those are our keywords.

Look out for them later on in the lesson.

Now, strategies to increase water supply.

We've got two key questions.

The first is how can we increase the water supply? And then secondly, we're going to think about how has California's water transfer project helped.

But before we jet off to the USA, let's stick with how can we increase the water supply? With a growing global population and wealthier populations consuming more, how can we increase the global water supply? So we're gonna look at four different strategies.

We've got diverting supplies and increasing storage.

We've got dams and reservoirs, water transfers, and desalinization or desalination, sorry.

Diverting supplies and increasing storage.

This is when water is not needed now, and it's stored underground in aquifers as groundwater for future use.

This strategy was used in Perth, in Western Australia, and I've got that map there to locate it for you, because millions of litres of wastewater were being dumped into the sea.

So instead, this wastewater is now being treated and pumped into aquifers for use in the future.

Real-world example.

Diverting supplies and increasing storage.

What advantages does this technique have? It helps to recharge or refill aquifers that are already overused by human activities.

And we can see the diagram there demonstrating where the aquifer is found.

Below porous rock, but above impermeable rock underground.

Where there are wet and dry seasons, water can be abstracted from rivers during wet seasons and stored for use in dry seasons.

Where high temperatures mean high rates of evaporation from rivers and lakes, diverting water from underground storage reduces water loss from surface evaporation.

So a number of advantages to this approach.

However, there are some disadvantages.

Expensive technology is required for recharging aquifers and monitoring their levels.

It can only be used where suitable aquifers are near the surface.

Too deep means the whole process becomes too expensive.

And if the water used to recharge the aquifer is contaminated, the whole aquifer will become contaminated, so it's at risk, limiting its future use.

So significant disadvantages to take into account.

Check for you here.

Which of the following is the term used for a layer of permeable rock that can contain groundwater? Is it a, aquifer, b, impermeable layer, c, reservoir, or d, water table? Pause the video now and discuss it with a partner.

And if you said aquifer, you'd be absolutely right.

Remember I asked you for a layer.

And if you said water table, water table is the top surface of that aquifer, okay? We wanted the name of the layer, which is the aquifer.

True or false then.

Diverting supplies and increasing storage are particularly useful in regions with wet and dry seasons.

I want you to think about that, and then I want an explanation of your answer.

And if you said true, why was that? Our explanation is as follows.

"Where there are wet and dry seasons water can be abstracted from rivers during wet seasons, if there's more water than needed, and stored for use in dry seasons when there may not be enough river water or rainfall to meet demand." Okay, so dams and reservoirs.

So rivers are dammed to create reservoirs, storing huge volumes of water.

This water can then be released when it is needed.

Perhaps you live near a reservoir.

An example here, an international example, is the Three Gorges Dam on the Yangtze River in China.

The Three Gorges Dam supplies drinking water, hydroelectric power, and increases river navigation.

Oh, and reduces river flooding downstream.

So lots of different benefits to that project.

So the advantages then of dams and reservoirs.

Reservoirs provide a reliable year-round supply of water.

As well as increasing water supply for drinking water, they can also be used to generate electricity through hydro, hydroelectric power.

Dams and reservoirs can be constructed at a range of scales, from very small to very large, to meet the needs.

What are the disadvantages of dams and reservoirs? Large dams are very expensive to construct and to maintain.

An estimated cost of building the Three Gorges Dam was 27 billion pounds.

People are displaced from the area that is flooded to create the reservoir.

Over a million people in the case of the Three Gorges Dam.

So a significant disadvantage.

And then thirdly, sediment carried by rivers feeding into a reservoir is deposited and builds up over time, reducing the reservoir's capacity, the amount of water it stores.

So remember I when was talking about kind of a guaranteed supply? Well potentially in the longer term that supply is not guaranteed if the reservoir's gradually filling with sediment and its capacity is reducing.

True or false then.

Dams and reservoirs guarantee a reliable water supply for many years into the future.

Think about that answer, and then remember I need an explanation in a moment.

And if you said false, what was your explanation? We had, "Although dams and reservoirs do provide a reliable and easily controllable source of water, this supply is not guaranteed.

Over time, sediment will build up and reduce the capacity of the reservoir.

Also, reservoirs can dry up during periods of drought." So we need to have some nuance there, don't we, when we talk about a guaranteed supply? Okay, water transfers.

Water transfers move water from an area of surplus to an area of water deficit through rivers and canals or through pipelines.

And here we've got a map of all the major water transfers that transfer water either within England, or from Wales into England, and within Wales.

The UK has several water transfer systems as we can see.

For example, water from the Elan reservoirs in mid-Wales is transferred to the city of Birmingham.

A considerable distance.

So these are big civil engineering projects, aren't they? Their advantages are that they balance the availability of water where there are areas of water surplus and deficit.

Some water transfers work by gravity rather than needing energy to pump the water, and they support economic development in areas of water deficit, while potentially creating some jobs in areas of water surplus.

So taking areas from mountainous regions which might be sparsely populated to areas where there's a real demand for water due to urbanisation.

In the photograph we've got a pipeline that carries water 42 kilometres from the Silent Valley Reservoir in the Mourne mountains to Belfast, the city of Belfast in Northern Ireland.

What are the disadvantages of water transfers though? Water transfers are very expensive.

I'm sure you guessed that one.

They're very expensive to construct and to maintain.

For example, the Elan Valley scheme cost about 6 million pounds to build, or it cost that in the 19th century.

It would cost much more now, wouldn't it? Transferring water from one region to another can spread invasive species more widely and disrupt river flows.

And water transfers into drier water deficit areas can encourage overuse of water in the receiving area.

An example is over irrigation, which can in turn cause soil salinization, which damages the soil.

Now there's some sort of key disadvantages there as well as we've heard about advantages.

Try and keep those in mind when we look at our real-world example in the second learning cycle.

Check for you then.

Which of the following are disadvantages of water transfer strategies for increasing water supply? So have a read through a to d, and then restart the video when you think you know the answer.

And if you said a, water transfer schemes can encourage overuse of water in deficit areas, you are right.

That's a disadvantage.

And if you said d, they can spread invasive species more widely, you are also right, well done.

Desalination.

So industrial processes such as reverse osmosis or distillation can remove the salt from salt water making it drinkable.

We've got a diagram here laying out the process of desalination, sorry, using reverse osmosis.

So we can see the sea water intake, a process of filtration, followed by reverse osmosis, remineralization, and then storage.

But then we've also got this outlet where we've got the leftover brine being released into the sea water.

Maybe gives you a clue about possible disadvantage of this process.

But it's an industrial scale process.

It takes a lot of processing of the water here, doesn't it? Clearly this looks like it's a costly process.

Let's find out.

Firstly then, advantages.

It provides a reliable source of water that does not depend on rainfall or river flow.

It can reduce the strain on other sources of water, for example, where rivers and groundwater are at threat from over abstraction.

And many large cities are located on the coast, so desalination can be useful in helping to meet the high demands for water from large urban populations and urban economies.

Here's an example close to the coastal city of Barcelona in Spain.

Downsides then, because I was talking about cost wasn't I? Desalination is very, very energy intensive, which makes it expensive, and also it gives a high carbon footprint unless energy comes from renewable sources.

A waste product is brine, saltier than seawater, which is harmful to marine organisms when it's released back into the sea.

Desalination can encourage wasteful use of water in regions where water supply could be increased more cheaply and with less environmental damage through conserving water and using it more efficiently.

So some significant disadvantages there as well as our advantages.

It kind of boils down to the geography, doesn't it, and where it's absolutely essential? Match the strategy.

Here's a check for you.

Match the strategy to increase water supply with its advantage.

So pause the video now, have a read through.

We are looking for four matches.

Okay, how did we get on? So we've got diverting supplies and increasing storage has the advantage of helping to recharge aquifers that are already overused by human activities.

Dams and reservoirs can also be used to generate electricity through hydro or hydroelectric power.

A water transfer balances water availability where there are areas of water surplus and deficit.

And we've seen that within the UK, haven't we? Desalination provides a reliable source of water that does not depend on rainfall or river flow.

Well done.

So we have a practise task for you here, so grab a pen.

Complete the fact file on these strategies to increase water supplies.

We've got three of the strategies there, and we need to fill in the blanks to talk about how it works, an advantage and a disadvantage.

Second task for you then.

Jakarta is a city of 11 million people in Indonesia.

Overuse of its groundwater has led to contamination of his aquifers with salt water.

What strategy would you recommend to increase water supplies in Jakarta? Consider different options in your answer.

So this is a kind of a suggest question, but you need to evaluate at least two different options.

So pause the video now, and make a start on those tasks.

And when you're ready to check your answers, restart the video.

Okay, how did you get on? So we had these three strategies.

And for the first, diverting supplies and increasing storage, you had to come up with a disadvantage.

We have, "There is a risk of spreading any contamination to the whole aquifer." So that's the risk of artificial recharge of aquifers.

Dams and reservoirs.

Well how they work, we've written, "Rivers are dammed to create reservoirs, storing huge volumes of water." Now there are various advantages, but we had, "Reservoirs provider reliable," perhaps we should have fairly reliable, "year-round supply of water." Desalination.

How it works is that industrial processes remove the salt from salt water.

Now what did you have for the disadvantage? Here we have, "Energy intensive: so high CO2 emissions, high carbon dioxide emissions, if not powered by renewable energy." So a significant disadvantage of that particular approach to increasing water supply.

Then we had our suggest question, didn't we? What strategy would you recommend to increase water supplies in Jakarta? Well I wonder what you had.

We had the following.

Remember you need to talk about more than one strategy.

"Because of Jakarta's existing saltwater contamination problem, increasing storage by using aquifers would be difficult.

It is located on the coast, so desalination is an option.

Jakarta could then have a reliable source of water for its very large population.

However, desalination is very energy intense and expensive so it may not be a sustainable solution.

Another option could be to dam a river to create a reservoir that could supply Jakarta with water.

While dams do displace people from the flooded area, which might be a problem on the intensely-populated island of Java, they ensure a fairly reliable source of water and can also generate hydroelectric power or hydro energy." Did you have something like that? Can you see how we've picked out a number of different approaches? Okay, well done on that task.

So the second half of the lesson, we're going to try and answer this question.

Has California's water transfer project helped? Where in the USA is California? I wonder if you know.

Well here I've highlighted the state of California because it's a coastal state in the west of the USA.

So we know where we're talking about now.

Let's zoom in a bit.

California is famous for its booming cities, such as Los Angeles, LA, San Francisco, and San Jose in Silicon Valley within the San Francisco Bay area.

California's population, like its economy, has grown over time; almost doubling in the last 50 years to reach 39 million in 2024.

This has been made possible in part by a major water transfer scheme within the state.

So let's have a look at that scheme.

Here's a diagram showing the overall scheme that has been overlaid on our topographic map of the state.

And you can see it is extensive.

The California State Water Project, SWP, collects and transfers water from the Sierra Nevada mountains of Northern California and distributes it to central agricultural areas and southern cities.

Additional water supply was needed, so this is linked to the aims of the project, to irrigate food and cotton crops in the Central Valley and support the economic development of the southern region with its arid climate.

If I add the arrows, you can see how that water is being transferred.

And the big blue bubble there is Lake Oroville, which is one of the major stores where most of that water is being collected.

We'll have a look at that in a moment.

Using GIS we can examine the pattern of precipitation across the state.

Annual precipitation is a layer that I've added on top of a topographic base map which shows the land's relief.

So we've got part of the state, or most of the state of California, framed here using the geography visualizer.

The northern part of the Sierra Nevada mountains is the wettest area within that range.

That's where we can see the dark blue.

Adding a layer of information about where California's cities are located, so can you see those red blobs, we can see the difference between where people live and where water availability is greatest.

You'll notice I've just damped down the transparency of that rainfall layer, so we're not overpowered by the yellows and the blues.

Red circles locating cities are larger for larger populations.

So I was using the red circles to represent population.

What do you notice about the patterns of rainfall on the one hand and settlement on the other? Well we've got the comment here.

"There's a bit of a mismatch with the largest cities in the south." And I'd absolutely agree with you.

Look at the size of Los Angeles.

And I've cropped off San Diego.

At 3.

9 million people, Los Angeles is more than three times the size of San Jose in Silicon Valley and seven times the size of Sacramento, the state capital in the north.

Very close to where all that rainfalls.

Oroville is a small northern city with a much wetter climate compared to LA.

With a population of 20,000 people, Oroville is an area of water surplus.

And you've got those rainfall totals for those two areas there 'cause I've been able to use the geography visualizer to zoom in and actually get a rainfall graph for that particular area, Oroville.

So you've got 1,220 millimetres per year compared to Los Angeles, less than 600, so 538 millimetres per year.

Quite different.

Lake Oroville collects water from the Feather River, a tributary of the Sacramento River.

It was created by the construction of the tallest dam in the USA.

The reservoir provides more than 60% of the State Water Project's storage capacity.

And it prevents flood damage, absorbing huge volumes of water during periods of extreme rainfall.

A recent example would be 1997.

The ambition of the civil engineering project is huge, like lots of things in the states.

California's State Water Project comprises of 21 dams and more than 1,100 kilometres of canals, pipelines, and tunnels.

Here we can see an area where the major California Aqueduct flows through irrigated fields, fields in Central Valley.

And remember that those green squares there are actually made possible by the flow of water.

So taking water from that canal and using its irrigate crops.

Construction began in 1960, and water was first transferred to the Bay area in 1962.

Central Valley, it reached in 1968, and in 1973 the scheme reached Southern California.

Here I've framed on the geography visualizer kind of the major extent of the area of this State Water Project.

I've labelled Lake Oroville, which we've talked about, San Francisco and Los Angeles, major recipients of the water within this scheme.

And then you've got Clifton Court intake and Edmonston pumping station, which marks the kinda major extent of the main canal, which is known as the California Aqueduct, transferring water south.

If I use the measuring tool on the geography visualizer, I can actually kind of sense check what I've been reading about the California Aqueduct being 489 kilometres long.

If we just take a very simple straight line measure of the distance between that intake we talked about and the major pumping station before the aqueduct branches, that measures at 400 kilometres.

But of course this water transfer scheme isn't exactly straight like that.

Edmonston pumping plant lifts water 587 metres up and over the Tehachapi Mountains.

And that's the point we were talking about at the point where the main aqueduct branches in the south.

Despite its huge capacity for power generation, when we talk about the whole scheme due to the design of the scheme and the relief that the water must be pumped up and over, the project is a net user of power.

Overall, it consumes 5,100 gigawatt hours of power per year in addition to the hydroelectric power it generates, so it's a net consumer.

Water must be lifted, as I say, up and over the Tehachapi Mountains to reach Southern California where you have these people in California that need the water in LA.

Has the State Water Project helped? Well, that's a good question.

And here we've got an image of grapes that are irrigated in the San Joaquin Valley in southern Central Valley.

It's estimated in fact that California State Water Project supports $400 billion worth of the statewide economy.

It supplies water to more than 27 million people.

70% of that goes to urban areas.

And 30% is used for irrigation, irrigating more than 300,000 hectares of land.

So I mean on a very basic level, has it helped? It's helped a lot of people.

True or false? California's State Water Project has boosted the local economy.

Is that true or false? And remember I need an explanation.

And if you said true, why was that? The explanation we have is, "The scheme supports $400 billion of the statewide economy.

And 30% of water transferred by the scheme is used for the irrigation of crops in Central Valley." So it's a major economic benefit.

California's income from agriculture is twice that of any other US state.

Wow.

Now here I've zoomed into a delta region, which is kind of within the central area of the overall aqueduct.

And I've labelled the Sacramento River and then highlighted that Clifton Court Forebay, which is the intake we were talking about at the start of the California Aqueduct.

Now at the northern end of the California Aqueduct, as I say, the Clifton Court intake is a small reservoir where water is taken from this delta, the Sacramento-San Joaquin River delta.

You can imagine water is being extracted from that system, and that affects the flows within the delta.

So now we're thinking about the impacts of the transfer project.

There are environmental impacts of dry season removal of water from this delta system because it's very sensitive.

Due the effect of the pumps that export water from the delta, the water actually flows north-south rather than east-west, disrupting fish migration routes.

A fish called the Delta Smelt is seen as an indicator species for the health of the delta ecosystem and is near extinction.

The flow of fresh water to the sea is half what it once was, causing a buildup of salinity in the eastern delta 'cause it's no longer flushed by the natural inflow of fresh water.

Increased frequency of cyanobacteria blooms in the delta over the past two decades have posed a risk to humans and animals on contact.

That's another environmental impact.

Here I've used the Wayback app.

And I just thought we would look at an aerial view of Lake Oroville.

So this is the winter of 2011.

And we're going to, sorry this is February, 2014.

And I'm gonna compare that in a minute with the same period of time in 2023.

But let's just start off with my fact about this.

The winter of 2011 to the spring of 2017 was the driest in California's recorded history.

So then this aerial image of Oroville Dam and Lake in February, 2014, we can see there's been some recession, hasn't there, around that? We can see some kind of sandy coloured banks of the reservoir.

In 2014, authorities announced that this project would be making zero deliveries of water that year due to low snow and rainfall impacting the reservoir.

So remember, let's compare February, 2014 to February, 2023.

Quite different, I think you'll agree.

In 2024, water delivery was at 40% of requested supply.

And we can kind of see why, can't we? There was a drought from 2020 to 2023.

And using the Wayback app, we can see the impact of that drought.

Look at the major, major recession of that dark green area, which is the area of water within the reservoir.

Very different.

With storms in late spring of 2024, by that June Lake Oroville was full again.

But increasingly supply from California's project is not guaranteed.

Drought in 2021 meant that the hydroelectric plant at Oroville Dam was shut down due to low water levels, affecting power available to pump water across the state.

Check for you.

Which of the following are disadvantages of California's State Water Project? Have a read through those, and then restart the video when you have an answer.

And if you said, "Well, a and b are both disadvantages," you'd be absolutely right.

The other two are advantages.

Okay, so we have some tasks for you here.

Using GIS, if you've got access to it, can you locate California State Water Project in terms of some of the key aspects? So I want you to find the Lake Oroville, the Sacramento-San Joaquin Delta, and LA.

Once you've done that, you'll be in a position to describe the geographical extent of the water transfer scheme.

And then I'd like you to explain the following statement.

The State Water Project's aim was to, and this is a quote, "correct an accident of people and geography." Then if you can outline the advantages and disadvantages of California's State Water Project, that would be brilliant.

Okay, so pause the video now, you've got some work to do, and then restart it when you want to check your answers.

Okay, so using GIS, I asked you to locate these elements: Lake Oroville, the Delta, and Los Angeles.

How did you get on? You were asked to describe the geographical extent of the whole scheme.

And I've written, "It involves the transfer of water from the Feather River, a tributary of the Sacramento, in Northern California southward.

Water is transferred to the delta and onward to San Francisco and Los Angeles via 1,100 kilometres of pipes or canals." Well done if you've got something like that where you've got an idea of the scale, we've got some named places, and potentially you've talked about maybe the number of kilometres the water travels.

Secondly, you're asked to explain the following statement about correcting an accident of people and geography.

We have the following.

"The project aimed to supply water to people in Southern California, where cities were growing in a region with an arid climate.

Northern California's physical geography, including its relief, for example the Sierra Nevada mountain range, means it has a much wetter climate than Southern California, but fewer people live in its cities.

Therefore, with a surplus in the north, water could be collected and transferred to more southern cities as well as Central Valley to enable the irrigation of crops." So that's the explanation of that quote.

How'd you get on with that? Then we had to make a quick summary of the advantages and disadvantages of California's project overall.

So here we have, well, its supplies water to 27 million people.

That's a key stat, isn't it? And it provides water to irrigate 300,000 hectares of Central Valley.

There are some disadvantages.

Dams, canals, and pumping stations need constant maintenance, adding cost to the huge initial investment, increasing bills.

And supply is not guaranteed as seen in 2014 when no water was transferred.

Couple more for you here.

So advantages.

Helping to ensure California's food security and supporting $400 billion of the statewide economy.

The last one was Oroville Dam prevents flood damage, remember? But the disadvantages are it's energy intensive and it's a net user of energy, despite 21 dams and its capacity for hydroelectric power generation.

It also disrupts the natural functioning of that delta ecosystem, including fish migration.

Well done if you got on all right with those practise tasks.

Now let's think about what we've done overall.

In summary, different strategies can be used to increase water supply.

Strategies to increase water supply, include diverting supplies and increasing storage, dams and reservoirs, water transfers, and desalination.

The California State Project is an example of a large-scale water transfer scheme.

Its development has had advantages and disadvantages for people, the economy, and the environment.

Okay, so we've covered quite a lot there and looked at a really interesting located example.

Well, at least one.

So well done on all your hard work, and I look forward to seeing you again soon.