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Natürliche Wasserqualität

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Natürliche Wasserqualität

Wie sieht es aus mit der Wasserqualität in der Schweiz? In Kapitel 5.1 lernen Sie Grundlagen der Wasserqualität sowie Verschmutzungsquellen näher kennen. Im Anschluss werden mit einer Bierbrauerei und einem Thermalbad zwei Industriezweige gezeigt, für welche die Wasserqualität eine wichtige Rolle spielt. In Kapitel 5.2 wird dann die Wasserqualität von Schweizer Gewässern anhand zweier Beispiele näher betrachtet. Darüber hinaus wird angeschaut, welche Auswirkung auf die Biodiversität in Gewässern die Wasserqualität hat.

Wasser in der Schweiz. Tauchen Sie ein! Woher kommt das Wasser in der Schweiz? Was ist ein Jahrhunderthochwasser? Wie viel Wasser braucht die Schweiz? Warum ist Wasser so wichtig für die Schweiz? -- Wasser ist so zentral für unser tägliches Leben und trotzdem ist das Wissen über Wasser häufig begrenzt. Dieser Kurs beantwortet viele Fragen rund um das Wasser in der Schweiz – schwimmen Sie mit! In sieben Modulen berichten verschiedene Wasserexperten über die vielen Aspekte des Wassers in der Schweiz. In den ersten Modulen eignen Sie sich verschiedene hydrologische Grundlagen an und erfahren mehr zu Niederschlag, Abfluss und wichtigen hydrologischen Konzepten. Auf diesem Wissen bauen die weiteren Module auf, in denen dann Themen wie Wasserqualität, Hochwasser und Wasserkraft behandelt werden. Mit einem Einblick über die Bedeutung von Wasser für Kultur und Kunst wird der Kurs abgerundet. Lernen Sie mehr über die hydrologischen Bedingungen in der Schweiz, staunen Sie über die Vielfältigkeit des Wassers und erfahren Sie, wie das Element Wasser den Alltag in der Schweiz prägt.

Visualiser le programme de cours

Enseigné par

Jan Seibert
Prof. Dr.
Ilja van Meerveld
Senior teaching and research associate
Daniel Viviroli
PD Dr.

Transcription

In this lecture we'll talk about water quality.

Even the clearest water still contains more than just water.

As water flows through the soil to the ground water or the stream, it dissolves

substances it encounters along the way, or it may deposit some of its constituents.

Soils contain high concentrations of carbon dioxide.

This creates a weak acid that dissolves many silicate minerals.

The eventual chemistry of the water depends on the rock and

soil formations through which the water flows, the temperature, and

how long the water stays in the ground.

Usually, faster flowing water dissolves less material,

as a result most natural water contains minerals.

The most common minerals are bicarbonate, sulfate,

sodium, chloride, calcium, magnesium, and potassium.

You can see which minerals are in the water when you pick up a bottle of water.

If you look at the label,

it will tell you immediately which minerals are in the water,

as well as whether there's any nitrate that usually comes from fertilizers.

Which minerals are in the water depends on the type of aquifer that

the water comes from.

Water flown through carbonate aquifers is mainly rich in calcium and bicarbonate.

Water from crystalline aquifers can contain more sulphate, but water from

the alluvial aquifers, and the mollase aquifers may contain more magnesium.

Hard water is water that has a high mineral content.

Hard water is formed when water flows through limestone and

chalk, they are calcium and magnesium carbonates.

Hard drinking water may have a moderate health benefits,

but it can cause serious problems in industrial settings

because it leads to costly breakdowns of boilers and cooling towers.

Municipalities may soften the water by using an ion exchange resin.

This replaces some of the calcium ions by sodium or potassium.

So even though this map tells you roughly where you can find hard water,

your local tap water may actually be soft water.

If your water doesn't really create suds or foam when you add soap to it, and

if you have a lot of limescale in your kettle,

then your drinking water is probably hard water.

Some minerals are in the water in only very low concentrations, for

example fluoride, which may have a health benefit, because it's good for your teeth.

Other minerals are less healthy, for example uranium and arsenic.

Arsenic itself is not toxic but

when it becomes oxidized it create compounds that are toxic.

You may have heard about arsenic contamination of ground

water in Bangladesh.

In Bangladesh one in five wells is contaminated with arsenic above

the government's drinking water standards.

But relatively high arsenic concentrations can also be found in some areas in

Switzerland.

For example, in the thermal waters in northern Switzerland,

iron rich chalk layers in Asura, and certain areas of the Alps that and

fibrillate bedrock, and also sometimes in granite bedrock areas.

The color of the water can sometimes tell us what's in the water.

For example, a reddish color may indicate that there is some iron in the water.

Similarly, a tea-like brown color near wetland areas

can tell us that there is a lot of carbon in the water.

But usually the color of the water tells us more about the solid

particles that are in the water.

As water flows over the soil surface, it can pick up soil particles and

transport them to the river.

Here we see the confluence of the Limmat with clear water from Lake Zurich and

a Sihl that has brown water and

high sediment concentrations after several days of rain.

Here in Geneva,

the River Arve comes from the northern side of the Mont Blanc massif and has

much higher concentrations of silt than the Rhone that comes from Lake Geneva.

This results in the striking contrast between the two rivers.

Because the Arve receives the water from many glaciers in the Chamonix Valley,

its color is sometimes milky white.

Rivers from glaciers contain rock flour and glacier flour,

which consist of fine grain silt-sized particles.

They are generated by the mechanical grinding of the bedrock by the glaciers.

Because these rock particles are very small they are suspended in the water

which makes the water look milky or cloudy.

The rock particles in these glacier rivers contain almost no clay minerals or

organic matter.

This makes the river look white and not muddy-brown like the other rivers

that contain more clay minerals and organic matter.

Alpine lakes are often turquoise or emerald green.

This is not because they do not contain any particles, but in fact they are so

blue because the particles are so small that they float in the water.

The glacial flour doesn't sink, and it reflects the wavelengths of the light

that fall in the bluish and greenish end of the spectrum.

That makes these lakes appear blue or green.

Water clarity is usually measured with a Secchi disk.

A Secchi disk is a disk that has two black and two white areas.

You lower the disk in the water until you can no longer distinguish the black and

the white areas from each other.

You can easily make such a disk, and

start taking water clarity measurements in your favorite lake.

Basically, you measure how deep you can see in the lake to make water

clarity measurements, you could also have walked into the lake and

check at what depth you can no longer see your feet.

In this lecture we've talked about natural water equality.

In the next lectures, we'll talk about pollution.

We look forward to seeing you there.

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