From the idea to the finished object

Section through purification biotope

Water can be a problem in urban open spaces. Building water features seems prohibitively expensive, too many things can go wrong, and maintenance is too expensive. But when the water quality is right, pumps, filters and control devices are working properly, the parts of the building that come in contact with the water are not damaged and when water, along with light and sound effects, turns boring places into exciting ones, no one wants to be without it. But however easily and light­heartedly water flows and splashes – it needs expert handling in urban landscapes.

Constructed water features are always individual objects. They emerge from interplay between the possibilities offered by the site and clients’ and planners’ ideas and wishes. The techniques used to install and run them are as varied as the water features themselves. They are rarely to be had off the peg, but need a technical concept that is individually tailored to their location.

But on the other hand there are always standards and guidelines to be taken into account, for example those apply­ing to the depth of the water or water hygiene. There are a wide range of regulations applying to these in different coun­tries. Experience shows that these can be interpreted individu­ally in terms of each particular situation. This is especially true if new and unconventional ideas are being realized: it is inno­vative concepts above all that mean thinking beyond existing norms. Here the key recommendation is that the responsible

authorities should be involved in the search for new solutions from the outset.

The following brings together a few hints on building and running water features that have emerged over the years from day-to-day work in the studio.

Sourcing and water quality

A fundamental criterion for the building and running of water features is the quality of the water. This is affected by physical, chemical and biological processes in the water itself and by its interplay with its immediate surroundings.

Water sourcing: Water features usually tap into the local water supply which generally means using drinking water.

It is also becoming increasingly attractive to think of using available surface run-off, drainage water or roof collected rainwater.

The origins and quality of water are crucial in terms of its possible use. When concerning a complex planning task, it is advisable to consult experts like limnologists to develop parameters for anticipated water quality. It is also important to identify questions about water hygiene and upkeep as quality requirements even during the design phase. Different standards apply according to the purpose for which the water is being used. The more the water comes into direct contact with people, for example with children playing, the more

From the idea to the finished object

bathing water quality is usually sufficient for features at ground level, or for pools.

The interplay between water and its built environment should be taken into account at the planning stage. Materials like concrete or mortar can have a significant effect on water chemistry, increasing the calcium content and raising the pH value of the water drastically. This can have a very negative effect on flora and fauna and in extreme cases damage the surface of materials.

Certain nutrients and germs will get into the water naturally by rainfall and can cause biological surface growth like algae or bacteria. The aim should be to keep this within tolerable bounds. Unrealistic expectations on the part of the client, like clear water that is free of algae at all times, should thus be discussed in advance. Such a requirement makes enormous technical demands that can only be met by using chemicals, UV filtration and other elaborate techniques. Using chemicals to purify water often turns out to be a dead end – it is expensive in the long run and ecologically dubious for the water. It can also create a number of peripheral problems, such as restricted plant growth or offensive odours.

Water is much more readily accepted when it is clear. For this reason attention should be paid from the outset to the rubbish and pollutants that will come into contact with the water and to their sources. Some things will fall into the water naturally, some as a result of human intervention. Fallen

 

open water is polluted by such materials, which are either dis­solved in it, or remain undissolved. It is therefore very impor­tant to know about any sources of pollution at the planning stage, and to estimate the nature and scale of their possible effects on the water feature.

The choice of which water technology is ultimately instal­led is influenced by all these prior considerations and investi­gations of processes in the water system. Courageous deci­sions about ecologically sensible solutions take pressure off the environment and can set new standards that lead to genuine innovation. Learning from nature and using the insights gained for new concepts is also a relevant planning approach here.

 

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From the idea to the finished object

From the idea to the finished object

From the idea to the finished object

 

General plan for plant room and circulation cistern

 

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of water. It is important that every storage reservoir or cistern is provided with an overflow as well as a drainage outlet so that it can be emptied and cleaned at regular intervals.

Pumps: It is seldom that a water feature can be set to run on a natural slope. Normally the water has to be circulated artificially with pumps. As a rule these are modern rotary pumps that are set up in either a wet or a dry state. Dirty- water pumps are recommended if high dirt levels are antici­pated.

Our experience is that it makes sense to run small foun­tains and watercourses with a circulation volume of up to 300 l/min with submerged pumps. But not all makes are entirely suitable for this. Submerged pumps are usually more reason­ably priced than dry-installed pumps, as they do not need their own control room and can be placed directly in the reservoir. They are more expensive to maintain than dry-installed pumps. Submerged pumps must always be set up so that they are sufficiently above the bottom of the feature to avoid clogging with mud.

Dry-installed pumps are recommended when several pumps are required or they have to be set up in sequence.

They are more accessible and thus easier to maintain, but they need adequate installation space. The best place is in a build­ing near to the water feature or a readily accessible service shaft. Here it is essential to build in a bottom outlet to the channel and also ventilation where necessary. Dry-installed pumps do not run silently even when fitted with vibration dampers; for this reason they should be sited so that sound

 

Construction elements

Water features cannot be built without technical equip­ment like reservoirs, pumps, filters and control devices. These are needed to purify the water, to store it and to control its circulation.

Storage and circulation cisterns: All water features with a circulating water system need a cistern or storage reservoir to ensure that there is always enough water available for them to run on. When small quantities of water are involved it is usually sufficient to install a cistern near the feature where the water can fall to by gravity. The cistern or reservoir has to be big enough for all the water to be stored after the feature has been switched off. The circulating volume consists of the amount of water circulating in all the pipes, channels and pools, and has to be specifically fixed for each feature.

It is not unusual for mistakes to be made when calculating for large volumes of water. The volume flowing out of a fea­ture must be the same as the volume flowing in. The smaller and narrower the outlet, the more the water will back up. This variation in water level has thus to be assessed as a volume and the water level has to be able to rise accordingly.

Water from the cistern is either brought by suction to the pumps in the plant room or pumped directly back into the circulation system by a submerged pump in the cistern. When features have a low-lying body of water like a pool or pond, these can be used as a reservoir and thus a separate cistern is not needed. Additional water is then fed directly into the body

 

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Bank zone

 

Drainage manhole

 

Circulation cistern

 

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emissions are kept reduced to a minimum.

The size of the pumps should not be decided until the volume of circulating water has been fixed. The manufac­turer’s technical specifications can be used as a guide. In the case of prototype features with special flow effects the size of the pumps should not be fixed without testing in a full-scale model. A certain circulation reserve should always be built in when choosing the size of the pumps so that the water quantities can be regulated if necessary. Maximum perfor­mance in relation to energy used can be achieved by pumps with automatic revolution speed controls, but this elaborate technology does not come cheap.

 

Filters: In nature water is continuously filtered in a number of ways such as percolating through vegetated soil, or by water animals. Filtering of this kind is also needed in artificial waters, especially when a lot of foreign bodies may find their way into it. Man contributes to this as well as nature – for example with plastic bags, cola cans, food scraps, plastic straws, cigarette ends and so on.

The first planning aim should always be to avoid dirt and rubbish entering the water in the first place. Where this is not possible the substances, which are often floating and do not dissolve, must be filtered out as soon after they enter the water as possible. In the case of circulation features this is done by coarse pre-filters like skimmers, rakes of perforated metal sheeting that are usually built into the feedback to the cistern. Various grades, from coarse to fine filtering, should be chosen, according to the amount of dirt involved. A filter with a mesh larger than 10 millimetres is considered coarse in this context. These should be simple and quick to handle, as otherwise manual cleaning tends to be carried out rarely or not at all. Stainless steel has proved its worth as a construc­tion material for these pre-filters.

It makes sense to use automatic filter systems as well as pre-filters in more complex features; as a rule they are instal­led on the delivery side of the pump. These filters, including fast sand filters and micro-sieves, are outstandingly well suited for removing fine particles like weeds or floating matter from the circulating water. Maintenance requirements are low, as these filters can be set to clean themselves automatically from time to time. Automatic filters should be fitted in the bypass

 

Section through equipment room

 

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Return pipes

 

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Operational diagram for circulation technology

 

From the idea to the finished object

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Pumps

 

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Pump well

 

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to the circulation tank, and should ideally be able to filter about 50 % of the total water in circulation.

We have found that naturally developed sand or bottom filters, here called purification biotopes, are suitable for many water features. They are particularly appropriate for features and systems that allow the watercourse to develop naturally to a certain extent, and that have sufficient space available. They have various advantages; they form second-hand bio­topes, do not need any additional energy and are not expen­sive to maintain. As with any other planting, dead vegetable matter and foreign bodies have to be removed from time to time. The winter months are most suitable for this.

Regulation and monitoring: Every water system needs regulation. This ensures that the various input points are pro­vided with the appropriate quantities of water at the required time. When the water level drops in the cistern or the body of water an electrical or mechanical sensor should monitor the water level and ensure that the necessary extra water is fed in. The control boxes and all the meters should always be instal­led above maximum water level in a separate shaft or in the cellars of an adjacent building. In the case of larger and more complex features there will be meters for certain parameters like pH value, temperature, oxygen content or nutrient levels in the water, working continuously or sporadically. These values then form a basis for precise analysis of the water.

Some clients like the feature to be monitored so that they can optimize development and also the maintenance of the system and the related costs on the basis of suggestions from experts.

Plant substrate Railway ballast 56/63 mm Sealing structure Drainage layer with pipe

From the idea to the finished object

From the idea to the finished object

Sound and light column

 

Light/sound technology: Lighting and sound effects are becoming increasingly desired by the client. They enhance the effects of a water feature and give the experience a new dimension, especially in the evening and at night. It is essen­tial to investigate the existing light and sound situation of the site, in order to assess their influence.

In many cases no elaborate electronic systems are needed. The interaction of air and water alone produces all sorts of sound patterns that can be used to good effect within a spa­tial concept. The rush of water has other qualities to offer than traffic noise, for example, and can be used deliberately to dampen or mask unpleasant noises and at the same time offers the opportunity to create a special atmosphere in a particular place.

Water cannot be lit like other objects. If artificial light is used, care has to be taken that the water itself can direct the light, and here reflected light is crucial. Before choosing a light source it is essential to conduct experiments to establish the desired effect of light on the water.

This effect is crucially dependent on the reflection of light from the surface of the water: it is only this that makes the water visible. Skilful light installation can also achieve these effects in twilight and at night.

If lighting is to be effective it is essential that the source points are positioned correctly. Lighting the water directly is not recommended, as the light would be reflected only at certain points. It is better to draw the observer’s attention to adjacent objects. They will be reflected from the surface and will produce the fluctuating images associated with water

 

with even a very little movement.

Lighting devices should be chosen in such a way that insects are not attracted in greater numbers, and to avoid increased weed growth in the water. This means that halogen lamps with a large UV output are not suitable; metal vapour lamps tend to be most used today.

Fibre-optic technology is particularly suitable for under­water lighting. The key feature here is that the light source can be placed at a safe distance from the body of water, and the fibre technology can take the light wherever it is wanted.

 

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From the idea to the finished object

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From the idea to the finished object

Tunnel roof

Construction technology

Technical aspects of construction are of crucial importance for interesting water features with high design values. Interest is focused on the following four areas: sealing, foundations, materials and connections.

Sealing: Natural seals like clay can rarely be used in built water features. There are many sealing processes that are quite close to nature, but a certain diffusion loss has to be anticipated with all of them. Such processes are suitable only when continuous supply and constant water level are guaran­teed.

When choosing a sealant the necessities arising from the specific situation have to be set off against the technical and financial input involved. The following criteria should be con­sidered: the qualities of the building land, the geometry and surface of the feature, the desired water quality, the planned building phases and the cost.

Water features that are supplied and drained naturally make fewer demands in terms of sealing than those that rely on an artificial supply of drinking water or rainwater. However, minimal water loss should be a prime consideration even for small water features, for ecological and financial reasons.

Plastic sheeting is very adaptable as a sealing material, and is well suited to features with complex contours and very diverse geometry. But natural forms can be constructed with it as well. Many water features have to take differing settling rates into account. Flexible sheeting is suitable here, as it is

From the idea to the finished object

Section through piazza ditch to tunnel roof

relatively easy to install on the spot, almost regardless of the weather. A whole variety of materials are available; of course their environmental friendliness must be given higher priority than technical suitability and economic viability.

If the substructure is something stable like concrete, for instance, a non-shrink grouting compound can also be used as a seal. It bonds firmly with the base and is simple to apply even if the geometry is complex. Coverings like natural stone slabs can be fitted directly to the rigid seal. This is also appro­priate for fixed materials like concrete and steel, but does not work with flexible connections or expansion joints; other seal­ing processes have to be used here.

Water features in the shape of simple and rigid structures can be built in non-permeable concrete. However, these are appropriate only when the subsoil is stable, certain dimen­sions are not exceeded and walls of an adequate thickness can be built. The statics of water-proof concrete make it parti­cularly suitable as a base for large prefabricated sections.

From the idea to the finished object

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From the idea to the finished objectFrom the idea to the finished objectПодпись: Section through concrete element run and watercourse

Foundations: Semi-natural lakes and ponds do not need rigid foundations. But fountains, pools and other built water features are particularly sensitive to subsoil settling, which can lead to cracks and leaks. What is usually needed here is foundations that can have a frost-free base and that are designed to meet the structural loading. The dimensions and thickness of the foundations are based on the weight, geo­metry, size and tolerance limit of the surface building.

Choice of materials: Unlike other structures, built water – features have surfaces that are always wet. For this reason it is important to use materials that are structurally stable and also frostproof in colder regions. Another important factor is that chemical and physical reactions of materials can be different and more aggressive in contact with water than in air, and vary with the characteristics of the water (pH value, temperature etc.). Building materials must be chosen to with­stand such processes in the long term. Water quality must also be taken into account when choosing materials, as substances dissolved out of mortar or concrete can have a lasting delete­rious effect on water chemistry.

In the case of earth and mineral substrates, chemical stability and the purity of the material are important factors. Organic components should be avoided wherever possible, as they raise nutrient levels and thus promote the growth of algae.

The colour of these materials is a key influence on the visual impact of the water; here dark shades are generally better for reflections on the surface of the water whereas-
lighter shades are suitable for showing reflections on the bottom. However, it is not so important to design the surface of these coverings elaborately, as the effect they make will be considerably reduced by the natural surface growth that occurs in any water. This growth can only be avoided by mechanical cleaning or the use of chemicals.

Water features in which people are intended to walk should have non-slip surfaces to minimize the risk of falling. Sharp-edged installations should also be avoided as they increase the risk of injury.

From the idea to the finished object

From the idea to the finished object

From the idea to the finished object

Concrete support structure Fan jet 6/60 mm Neoprene Water borderstone Mortar filling 45 mm Protective layer 3 mm Waterproof layer 2,5 mm Fleece 500 g/m2 Control sensor

 

Fitting the waterproof layer with adhesive strip

 

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Interfaces: Natural watercourses are always in a state of dynamic interchange with their surroundings, losing water through outflow, evaporation and infiltration. Artificial water features would quickly lose their water to the surrounding area. To prevent this, the interface is particularly important, as well as sealing.

The interface between inflow, outflow, pipes and walls always presents a potential danger in terms of leaks; this is where most problems occur in practice. Different construction methods are required according to the nature of the seal. Connections through sheeting require fundamentally different flange constructions from those used for pierced concrete, for instance. For this reason precise and early planning is needed here, and particularly careful attention must always be paid to the construction and detailing of these points. Some specialist manufacturers offer prefabricated pipe ducting for seals of all kinds.

From the idea to the finished object

From the idea to the finished object

Construction option 3 Waterproof bottom

From the idea to the finished object

Construction option 1 Construction option 2

 

Natural granite slab Railway ballast Gravel 5/25 mm Substrate

Protective layer 3 mm Waterproof layer 2,5 mm Fleece 500 g/m2 Control sensor

 

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