Water is universal

The water system in Berlin's Potsdamer Platz

Question after question cropped up on the top of the red Infobox in the middle of Potsdamer Platz, and deep abysses opened up in front of it. Colour­ful hard hats moved as though on invisi­ble strings, and so did the lorries, full or empty after they had tipped their loads out, divers poured the cellar foundations into the groundwater at night, coloured piping ran to and fro over streets and excavations, cranes raised and lowered everything that was needed inside and outside, up there or down here. Expecta­tions of the completed Potsdamer Platz were immense, and the problems on what was once Europe's largest building site were highly complicated. Two demands: people were not just supposed to work here, they were supposed to spend their leisure time here as well.

A vibrant urban construct was to be cre­ated, which is difficult in the shadow of towering company headquarters. And the intention of setting high ecological standards for the project had caught on as well. There were the following prob­lems: very little space was available for leisure provision, and it was subject to all sorts of demands and wishes. What devices for planning open space, what themes can be used to do justice to a lot of people and the urban design at the same time, and finally to come close to meeting ecological aims?

Herbert Dreiseitl had already worked on Potsdamer Platz immediately after the Wall came down, with an Anglo-Ger­man planning team. The theme of water as a defining element in the open space had convinced both the Senate and the investors from the outset. First of all the design possibilities caught their imagi­nation, and secondly they were fired by the chance of meeting the ecological challenges. The suggestion that rain­water should be used for flushing toilets and watering green areas was met with interest. The same was true of the idea of using the rainwater that collected in the underground tanks to feed a water

Visible water cleansing through a planted biotope does not just stabilize the water quality, but also adds a strikingly dune-like note to the austere urban landscape.

No parapet or railing - step­ping stones lead over the expanse of urban water.

Even when frozen over in winter, the water provides an interesting context for the architecture.

Everything comes together here: active life, prestigious architecture and a filigree pattern of water features that contain in fact just collected rainwater.

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Overflow

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Retention

Overall plan of the Potsdamer Platz site with

Water use

urban water features

Water storage in cisterns

Flow simulation analysing how the water acts within the geometry of the pool. This made it possible to optimise the most effect locations for the inlet and outlet points.

system that would include a narrow pool on the northern side, one in the piazza, the large main area of water and the southern area of water. Additionally, this offered the opportunity not to lowerthe groundwater during the building phase and to make an intermediate collection of all the rainwater that fell on the buildings and slowly feed it into the Landwehrkanal. A complex computer simulation was used to predict that the Land - wehrkanal would only be compel­led to absorb heavily increased amounts of precipitation three times in ten years; this is based on the approximate drain­age figures for an unsealed plot.

To guarantee this, the system must carry sufficient buffer capacity. This is provided in the first place by five under­ground tanks with a total volume of 2,600 cubic metres, of which 900 cubic metres are left free in their turn for cases of heavy precipitation. In addition to this, the main area of water can still offer a reserve of 15 centimetres be­tween the normal and the maximum water level, which provides a storage buffer of 1,300 cubic metres. A key fea­ture was the water resources that were discovered above the turbidity level of the main area of water. Solids can start to settle in the underground tanks be­fore the water flows out of source ves­sels on the banks of the south and main areas of water, through planted purifi-

Section detail through cleansing biotope

Circulation

Sony Center

Potsdamer Platz

Philharmonie

A2

A4

Weinhaus

A3

Hyatt-Hotel A5

Buro B6

Spielbank

IMAX B7

Wohnen B8

Theater

Staatsbibliothek

Wohnen B9

Debis

Hauptverwaltung

Hauptgewasser

Volksbank C2

Canarishaus

C3

The water system in Berlin's Potsdamer Platz

Scharoun's Berlin Philharmonie is reflected in the crystal clear water.

cation biotopes, where it is cleaned bio­logically and chemically. If necessary, technical filters can also be used, which will remove any floating algae in the summer months.

In Marlene-Dietrich-Platz water flows in intricate patterns to the lowest point in the piazza. The water glides of flow - steps from the main expanse of water,

Steps and sculpture platform in the mobile surface of the water

formed. A detail that is accurate to a

Architecture bathed in light, reflected and dissolved in the water

Turbulent rhythmic structures

The water surface is a mirror at night

Stippled waves, created by the tiniest possible change in levels, alternate with smooth and turbulent areas. The interplay of wind, nature and art produces visual colour games.

Water is far from being just a designer's resource or a material: it begs to have its vital possibilities rediscovered. This starts at the beginning of the planning process for water projects, and involves linking up and integrating elemental themes. Knowledge of water's particular quali­ties as a material are needed, and often experiments need to be conducted to give a real idea of the result that will ensue.

Water is everywhere in our towns, in a labyrinthine system of concealed pipes. It is freely available, and can apparently be disposed of without difficulty. City-dwellers are usually only confronted with it at the various ends of the system in their houses or flats: coming out of the tap into the sink or wash­basin, in the bath or under the shower, with the surge of the flush or when paying the water rates.

But nowadays it is rare to experience water in the open in our towns and cities - and yet it is increasingly in demand. Aesthetically presented and decoratively displayed, from a simple fountain to a showy water installation, it is appreciated as an invigorating element in front of and between the build­ings.

Of course fountains and open waterways in towns and cities are nothing new. There is impressive evidence of them even from ancient times. They give us a sense of how closely urban design has always been linked with water and its use. This functional relationship can be traced from antiquity through the Middle Ages to modern times, and has made a lasting impact on the image of cities. Waterways for goods transport and other traffic, facilities for providing drinking water and removing sewage were crucial when choosing a location and helped to shape the ground plan of a town, the squares and streets. And here water was far more than some­thing that simply had to be supplied and disposed of, it was presented artistically in all the great cultures, emphasized aesthetically and venerated. It created the atmosphere and expressed a living relationship between a town and its sur­rounding area. The way water is handled in towns shows more than the mere technical ingenuity of its citizens, it reflects myth and religion and shows the spiritual constitution of people living in a water culture.

This changed fundamentally during and after the indus­trial revolution: water and waterways were now increasingly brought under control. They were straightened, canalized, built over, buried and even filled in. Trusting entirely to the fact that all this would be technically possible. But this trust was broken by the floods, which came more and more frequently, and with increasing fury.

Now water is one of the key questions as far as the future of our world is concerned, as we have recognized that natu­rally available water supplies are finite, pollution is always just round the corner, and we are aware that water plays a complex role in the stability of eco-systems.

Water is the material basis of man's relationship with his environment, and often stands as a symbol of it. It creates links and is in a state of permanent exchange in relation to warmth, climate, air, soil and gravity. Growth, metabolic change and vital functions are inconceivable without water. Water projects are perhaps so topical because they express a profound longing for life in all its vigour.

Technology and aesthetics are usually kept neatly apart in our brave new urban world as contradictions that cannot be bridged. They often seem to be as far apart as the various pro­fessions and specialist disciplines associated with them - and so the various training courses are neatly separated as well.

Unknown water

Although we could not survive from day to day without water, we are usually aware of it only superficially and at particular moments. Reduction to simple functions like clean­ing, washing and waste disposal reduces the intricate inter­play of water with our lives to simplified and imprecise images.

Planning and working with water seem simple at first as well - but even the first practical experiences can reveal un­expected and unfathomable depths, and other surprises. For example, water often does not flow in the way that is projec­ted by the computer or on the drawing-board: a curtain of water falls quite differently from the way you anticipated, the desired wave patterns do not materialize, or are not as plan­ned, and the 'reflecting pool' you hoped for reflects too rarely - or not at all. And it is also not rare to find that the quality of the water in a newly installed system leaves something to be desired, or a deposit of limescale spoils the look of the expen­sive natural stone basin. Other consequences of such mistaken assessments and ignorance at the planning stage are techni­cal problems and excessively high running costs.

This is not a horror story, but unfortunately it is often the case - and there are a lot of architects, planners, artists and their clients who could tell you a tale about it, and who have foundered on one of these rocks. They then give up, following the motto 'once is enough', or are simply satisfied with going back to banal solutions that have been used all too often in the past.

And there are some places where new fountains and water sculptures can seem out of place or unnatural. This is a sign of approaches that have been worked out in theory, but have

nothing to do with the real qualities of water. Indeed there are times when people look at these fountains and sculptures and ask whether it wouldn't have been better to leave the water out altogether. Every artist and planner realizes when design­ing a water feature that water needs a great deal of respect when you are working with it: it is mysterious, and likes for be investigated sensitively. It is easy to assess when looking at projects and works of art involving water how thoroughly the people planning it understood water. Did the water in the pro­ject become a mere side issue, or is this a successful installa­tion that does justice to water and brings out its best quali­ties? Here at the latest you see whether the planner had real insight, and how sensitively the water has been handled.

First experience and approaches

The knowledge we acquire at school and from the rest of our education is often not enough to grasp water in all the richness of its many manifestations. You cannot get to the bot­tom of water with abstractions like chemical and physical for­mulae, as the ideas associated with them are often too static and distanced. Water is full of dynamism, and it needs a sense of movement in the thinking and ideas of the people dealing with it. Professions that handle water every day gain experi­ence of this kind and know the special inner flexibility that is needed to work with water successfully.

There are all sorts of ways of getting closer to this amaz­ingly flexible material. This includes a number of sports that make it possible to experience water directly and physically, using some quite simple aids: swimming, surfing or diving, to name but three. Sensitive observation of water in a landscape is particularly valuable.

Water and air: You have to start by watching what happens when it rains. The weather front approaches trailing a curtain in the sky, and the threads of rain dance in the wind like a fine veil. If you are lucky, different coloured layers appear in the depths, and sunlight is split into its spectrum in a rainbow. Whether it is a veil of rain, or mist and cloud formations - the images change constantly, influenced by temperature, humid­ity, air pressure and temperature variations. But water is visi­ble in air only when droplets or ice crystals catch the light.

Surfaces: If droplets fall into a lake from trees on the shore, you see a number of eccentrically expanding rings of waves, that seem to pass through each other without having any effect. Perhaps you can see from stalks, twigs and objects how the waves are diverted there, then break on the shore or are driven back again.

Wave structures with different patterns appear in all places where different media meet, e. g. on the borderline between
water and air. Here dimension or scale has only a minor role to play. A fine breath of air, the slightest stimulus is enough to produce an infinite number of rhythmic patterns in a pool or the sea, or even in a little basin. Here again it is worth noticing the play of light, as it is only reflections of the sky, the landscape or of objects that make the wave structures visible to us.

There are planes that appear on borders, and also waves, that are only seldom perceptible. This also includes horizontal interfaces between bodies of water, for example with different densities. These are caused by differences in temperature or different salt contents. We are often aware of them when swimming or diving in summer, and they can oscillate slowly from time to time, as a result of wind, variations in atmos­pheric pressure etc.

Eddies: A twig blowing in the wind in a lake, stones sticking up out of a stream, the piers of a bridge in a river - the atten­tive observer will notice a series of eddies produced by all these obstacles. Whole strings of eddies are made visible on the surface by differently reflected light. But most of the eddies in water remain hidden. They are to be found in a large variety of unseen forms, in all waterways. It is not until traces of sand start drifting with the water, or colour is provided by clay or mica-schist, that all this diversity becomes visible.

Meanders: Even small watercourses, like melting glacier water, trails of water trickling over fields of sand below the tongue of a glacier in the mountains, shapes left behind by the falling tide on the beach or glacial valleys that have not been dammed show water's natural tendency to meander.

These examples could continue. A great deal can be observed in nature, but she does impose limits. Random factors caused by a whole range of parameters and conditions that are often unfavourable to precise observation limit perception. And therefore some questions can only be inves­tigated by experiment:

Experimenting in order to understand water

Even though flow movement in water does follow certain laws, about which we know a great deal today, the specific ways in which they develop are full of surprises. Experiments can be very simple. The more minimal their construction the more astonishing the results often are.

A smooth, water-resistant sheet, as polished as possible, made of something like glass, perspex or wood coated with plastic, is placed in a diagonal position. Water flows on to the highest point of the sheet from a small diameter hose. You expect a thread of water to trickle down in an absolutely straight line, following the shortest possible route according