Mega lake for the city of millions

Singapore is not poor in water. On the contrary: it is surrounded by sea. But what the city of 5 million needs is not salty seawater. Drinkable fresh water is in demand. That is why the city-state built a huge dam for its water supply: “Marina Barrage”!

Until now, Singapore bought almost all its drinking water from its neighbour Malaysia. Millions of litres flowed into the city from there every day. But Singapore wants to become independent of Malaysia, because the relationship is tense. For this reason, the city began building a gigantic dam in 2005. A 350-metre-long dam made of reinforced concrete now shields the Singapore River from the open sea. Nine movable gates control the water level. Huge pumps can transport the water masses into the sea in case of a storm surge or tropical rainfall. Behind the huge “Marina Barrage” wall, a freshwater lake has been created in the middle of the city. Even if the water is still brackish and salty at the moment, the “Marina Reservoir” should provide clean drinking water from 2015.

Marina Reservoir and the walkable dam Marina Barrage have become a tourist attraction. Singaporeans also use the area in their leisure time. But only electrically powered boats are allowed on the lake. After all, it is supposed to help quench the enormous thirst of an entire city in the future.

No land in sight

Nowhere in the world are you further from the mainland than at Point Nemo. That is why it is also called the Water Pole or Pole of Inaccessibility. Point Nemo is in the middle of the Pacific Ocean between Chile and New Zealand. It is exactly 2,688.22 kilometres away from Easter Island, Ducie Island and Maher Island. If you want to visit Point Nemo, you should remember its coordinates: 48° 52.6′ South and 123° 23.6′ West. However, nothing but water awaits those who head for it!

The tough battle for water

Long queues of people crowd in front of the wells in Zimbabwe’s capital Harare. Water is particularly scarce in the townships of the city of millions. Time and again there are fierce battles over the scarce commodity.

The nearly three million inhabitants of Harare need twice as much water as is available. Only wealthy citizens have access to their own wells; the poor are often dependent on aid organisations for supplies. A major problem is the pollution of the water. One of the city’s two reservoirs is so dirty that it can no longer supply drinking water. Because of the contaminated water, thousands of people already died of cholera in 2009. Harare’s inhabitants fear another outbreak of the disease. Because of the poor water supply, violence in Harare is increasing.

The situation in Harare is not an isolated case. Many developing countries in Africa, Asia or Latin America have the same problems. In total, more than one billion people on earth have too little or no clean drinking water. The growing world population and climate change will in all likelihood further aggravate the situation.

To milk the fog!

The Atacama Desert is the driest desert on earth. At its edge lies the northern Chilean city of Iquique – an Eldorado for fog experts. Because here the conditions for “milking” fog are dreamlike: High humidity and lots of wind.

Climatologists have stretched fine-meshed nets to collect the fine fog droplets. Small drops collect on them and fall into a collecting channel. This makes it easy to collect the moisture from the fog – at favourable locations a whole five litres per square metre per day. This can be used to obtain drinking water – which is extremely scarce in this dry region. Other low-rainfall regions with mountains near the coast could also collect drinking water in this way. However, it is questionable whether the method is suitable for combating future water emergencies. In such a case, “fog milking” would probably be more of a drop in the ocean.

A full bath for a cup of coffee

A bathtub full of water to make one cup of coffee – that’s 140 litres! It takes almost as much water to make one breakfast egg. Sheer nonsense? British geographer Anthony Allan has found otherwise. At the Stockholm World Water Week, he and the WWF (World Wide Fund for Nature) came up with an amazing calculation on water consumption.

Their calculation is not just about the one cup of water that is poured into the coffee machine, but the total amount of water that is needed to produce one cup of coffee. And this starts with the cultivation of the coffee plant, which has to be irrigated intensively. Water is also consumed in the transport and packaging of the coffee. If you add it all up, you arrive at the initially unbelievable 140 litres of water for a single cup.

But the calculation goes even further. A T-shirt contains 4,100 litres of water, a new car swallows around 400,000 litres. In this way, every German consumes around 4,000 litres of water per day. This includes water consumption such as drinking or washing as well as consumption in the manufacture of products. Each of us leaves such a water “footprint”, depending on how much water we personally consume. Because much of this consumed water is invisible, it is also called “virtual water”. According to this calculation, we take almost 30 full baths per day – purely virtual!

Aral Sea dried up

It was once the fourth largest lake on earth. But compared to its former size, the Aral Sea in Central Asia is now just a puddle surrounded by a barren desert landscape. The reason: huge cotton fields in Kazakhstan and Uzbekistan. Cotton cultivation in this dry region requires artificial irrigation. Since the 1930s, farmers have tapped the two large tributaries of the Aral Sea, the Amu-Darya and the Syr-Darya, and channelled the water to their fields. The result: the Aral Sea dried up more and more. As the amount of water decreased, the lake also became increasingly salty. This also had an impact on the fauna: of the more than 30 fish species that once lived in the lake, only six are now found in the salty lake.

The blue planet

Seen from space, the earth’s sphere appears a strong blue. This is because almost three quarters of the earth is covered with water. Although water is transparent in small quantities, from a certain depth it takes on an increasingly strong blue shimmer. Because we see the mighty oceans as blue, the Earth is also called “the blue planet”. The term is particularly true south of the equator. This is because the southern hemisphere is almost completely covered by sea, because a large part of the continents have migrated northwards due to plate movement.

The vast oceans contain almost all the water on earth. A lot of salt is dissolved in seawater, which is why it is not suitable as drinking water. What little fresh water there is on earth is mainly frozen in glaciers and ice caps. Only a tiny fraction of freshwater is found in groundwater, lakes and rivers or in the air.

But the view from the outside is deceptive: the Earth’s surface is largely covered by water, but measured against the diameter of the Earth, the oceans are only a wafer-thin layer. Therefore, the water makes up only a fraction of the Earth’s mass. By comparison, if the Earth were the size of a basketball, all the Earth’s water would fit into a ping-pong ball. And the drinking water would be proportionally even smaller than a single popcorn.

Drinking water

Colourless, pure and cool, without odour and without taste – this is how drinking water should be. It must not contain any pathogens, but certain minerals such as calcium, magnesium and fluoride. To ensure that the quality of drinking water is right, it is constantly tested in the waterworks’ laboratory. In Germany, drinking water is the best controlled foodstuff.

Drinking water does not bubble out of the tap by itself. It must first be treated so that it meets the high quality requirements. Groundwater is best suited for the production of drinking water. Because by seeping into the ground, the rainwater is pre-cleaned, as if by a filter. Pollutants and turbidity that are still in the water afterwards remain trapped in the filters of the waterworks. The clean water can finally be sent on its journey to the individual households via pumping systems.

Drinking water can also be obtained from rivers and lakes or from the sea. However, the water from these bodies of water is usually not as clean as groundwater. In addition, seawater must first be desalinated at great expense before it can be drunk.

The unequal distribution of drinking water

Turn on the tap and fill it with clean drinking water: It’s not as easy as it is here on earth. Although our planet is largely covered by water, there is a water shortage in many regions of the world. Even today, more than one billion people have no access to clean drinking water.

So far, the water shortage has been particularly severe in the dry areas of Africa, where it hardly rains. Here, people often have to walk for kilometres to the next river or well. But there is also a water shortage where fresh water is contaminated by bacteria. The countries affected often lack the money to purify the water in sewage treatment plants as we do or to desalinate seawater.

Water consumption varies greatly in the different regions of the world. The industrialised nations consume much more water than the developing countries. When it comes to water consumption, it is not only water for drinking and washing that is important. Where there is a lot of consumption, the “virtual water consumption” is also the highest. This is because much more water is used in the production of products than is apparent at first glance. This invisible water that is consumed in production is also called “virtual water”.

Experts suspect that more and more people will suffer from water shortages in the future. The growing world population and the pollution of water are decisive reasons for the dwindling supplies. But global warming is also likely to exacerbate the unequal distribution of water. In regions where flooding is already a regular occurrence, rainfall will increase. And very dry areas will probably receive even less rain.

How sweet is fresh water?

Although it does not taste sweet at all, it is called fresh water. Unlike salt water, it contains no or only very small amounts of salt and therefore has hardly any taste. For this reason, it is also well suited for obtaining drinking water.

Freshwater is rare: Of all the water on earth, only two to three percent is fresh water. Most of it is found in the high mountains and at the two poles. There it is stored as ice in glaciers. Only a very small fraction of the fresh water on earth flows in streams and rivers or splashes in lakes and groundwater. The water in clouds and precipitation is also “sweet”.

Fresh water is vital for us. To stay healthy, humans need about two litres of liquid per day; without water they can only survive for five to seven days. In addition, we need a large amount of fresh water for showering, washing clothes or dishes. Plants and animals that we feed on also live on water. Freshwater is even the habitat for many creatures: crayfish, pond and river mussels and freshwater fish such as trout, pike-perch and char.

How does the salt get into the sea?

Anyone who has ever swallowed water while bathing in the sea knows from personal experience: seawater tastes salty. And when the water evaporates, a fine white layer of salt often remains on the skin. This is because seawater consists of an average of 3.5 percent salt. For one litre of seawater, that’s 35 grams or about one and a half heaped tablespoons of salt. But how does the salt actually get into the sea?

Many of these salts come from the rocks in the earth’s crust. Rainwater dissolves salts from the rock and takes them with it. It washes them into rivers and groundwater. In this way, salts are washed into the sea. Because relatively little salt is transported, the river water is hardly salty. The concentration only increases in the sea. This is because salts from the ocean floor and from submarine volcanoes are added there. When the seawater evaporates, all these salts remain. This is why salts that have been washed out have been accumulating in the oceans for millions of years.

The salt content is not the same in all seas. The more water evaporates, the more saline the water becomes. The Red Sea contains more salt than the Pacific. And the Dead Sea in the Middle East – actually a lake – is so salty with a salt content of about 30 per cent that you can lie in it without sinking. In contrast, the Baltic Sea is rather low in salt: because of the low temperature, only little water evaporates there. In addition, many rivers flow into the inland sea and feed it with fresh water. That is why the Baltic Sea is much less salty than the Dead Sea.