Poor water management in Prague increases the risk of both flooding and droughts

9.8.2011 - PRAGUE

Water management in the capital does not correspond with the world trends. We are missing efficient measures to hold and use rain water, drinking water is unnecessarily wasted and the risk of flooding increases. The project of the Central Sewage Treatment Plant is oversized and too expensive. The (Prague) Municipality does not communicate with the public and green areas are being covered with buildings because of the territorial decision. That further worsens the water management and stands against the interests of citizens.  

This could be the summary of an international research/survey that was organized in Prague by the prestigious Dutch Wageningen University. The study, which is now being handed out to officers and politicians at the Municipality and municipal authorities, shows some possible solutions from overseas. The research was conducted in 2010 by thirty students from twenty lands, who study the Master program Urban Environmental Management at this Dutch university.

„An independent study can be helpful for experts at the Municipality and municipal authorities. They ought to consider modern conceptions of water management, while planning the city development, water becomes an increasingly valuable natural resource," said Martin Skalský from association Arnika. The researchers found out, that Prague citizens have at their disposal seemingly unlimited potable water supplies – especially the Želivka Reservoir – and they do not feel compelled to save. Drinking water is used for flushing toilets, watering flowers and washing. Whereas the world trend is to recycle rainwater, which is for free. Using rainwater also prevents water from slipping out from landscape so quickly and decreases the risk of flooding. Although Prague invests vast amounts of money into movable flood walls, no one takes care about water accumulation and absorption.

A useful solution for Prague could be the one form Chicago – its climate is different but it is in a similar stage of urbanization. Chicago's Municipality launched some projects that reduce costs of cleaning storm-water, hold it and absorb it. Community projects that improve water management. The authorities for example started lobbying for disconnecting gutters from the sewerage system. They also establish gardens (e.g. on parking places) for holding rainwater. Another thing that is worth mentioning is the project of supporting green roofs and even the Chicago town hall has a large garden on the roof. Since 2001 the city has been reconstructing some streets that used to be covered by asphalt with porous materials, which prevent local flooding and help water absorption. Similar systems could also be used in Prague.

After the devastating flooding in 2002 many measures were taken in the affected and vulnerable areas. The flood protection should first of all be integrated in the land-use plan, but that is not happening. According to the concept of the new Prague territorial decision and its altering, hundreds of hectares of fields, meadows and green areas should be turned to areas meant development-construction. The more asphalt and concreted area it is, the faster rainwater flows and the risk of flooding rises. Researchers warn that this would decrease the natural ability of landscape to hold water, and recommend the Prague authorities to get inspiration in the Netherlands.

Since the Prague sewerage system works both for sewage water and rainwater, the capacity of the Central Sewage Treatment Plant needs to be vast. And so cleaning of water becomes more expensive. The international study is surprised, that even though Prague is about to have 1,6 million inhabitants in the future, the plan of the new central sewage treatment plant is dimensioned for 2,2 million people. The researchers point out that decentralized systems are more effective – as we can see from the example of DESAR (Decentralised Sanitation and Reuse). DESAR is successfully working in several European cities and is based upon gathering, cleaning and using wastewater directly at the place it is produced. During the anaerobic decomposition energy is gained, and when sludge is used in the agriculture, nutrients are re-used. The decentralized systems could be used while constructing new buildings on the outskirts of Prague. Connecting to the sewing system is expensive there and agricultural land is close-by and using sludge is therefore effective. This would perfectly suit for example the district Štěrboholy – Dubeč, where new development is being planned and the local population is about to grow.

The Dutch Government has submitted a conception of secure handling of larger amounts of water called „Space for the River", which should – from 2015 on – improve both flood protection and the quality of ecosystems in the river basin. This means in particular reducing the river surroundings, removing dikes in the inland, reducing levees around rivers and enlarging the riverbed. Dike reinforcement will be used if, and only if other measures would be too expensive or unsuitable. The project is being executed in cooperation with all the lands in the river basin, for example with Germany.

The Prague research involved also a questionnaire survey among 550 randomly selected people from the monitored areas. For most of them the green and water areas are important and people are usually satisfied with the use of concrete areas. Almost half of people would appreciate new recreation areas, whereas almost two thirds are against further developers' constructions. Two thirds of people feel they have no influence over decisions about form of Prague and that the authorities do not communicate with them.

Here also the Prague authorities and politicians could get inspiration from overseas. For example the government in France organized in 2008 nationwide consultations of the draft of the river-basin management plan. Open discussions and exhibitions took place at the Loire river basin in Brittany, information centers were established, guided tours and theatres were visited. The consultations helped gaining support for altering the goals of the European Water Framework Directive of this river basin. Concretely the percentage of rivers that are going to be in a good condition till 2015 increased from 45 % to 61 %. 85 thousand people and 450 municipalities, civic organizations and associations expressed their opinion during the consultations. Other French river basins acted similarly.

Details and notes for editors:

Arnika's advices based on the study from the Dutch university:

1. Improve withholding water in the urban landscape, for example by using rain-gardens.

2. Do not build on large open areas – on the green and on the agricultural land.

3. Use porous materials while building streets, parking places etc.

4. Use rainwater for watering plants, washing and flushing the toilets.

5. Decentralize cleaning of wastewater, mainly on the outskirts of Prague.

6. Use new ecological technologies while constructing new building – for example green roofs.

7. Get the public involved into decisions about the city development.

Details about the DESAR-system

DESAR was introduced in the city Sneek in the noth Netherlands. The new residential area consists of 32 houses and has a system of gathering, conducting and cleaning wastewater locally. Household wastewater is gathered separately as „black water" (excrements and urine), „grey water" and rainwater. The mixture of black water and kitchen waste is being dealt with right on the spot with anaerobic decomposition.

Using this sewerage system in new residential areas has many positive effects: the water stays at one place, energy is gain by the anaerobic decomposition and the nutrients from sludge can be re-used in agriculture. Not only does this system cleaning the water from all common pollutants in wastewater, it also filters pollutants that are present only in trace amounts, like medicines and hormones.

The described technology can be applied while constructing new buildings on the outskirts of Prague. Connecting to the sewing system is expensive there and agricultural land is close-by and using sludge is therefore effective. This would perfectly suit for example the district Štěrboholy – Dubeč, where new development is being planned and the local population is about grow. The new sewerage system could be also a good opportunity for cleaning wastewater from a hospital being planned at Prague 7 on the place of the Bubny-station, since it is able to clean water from medicines and hormones.

More information about research at the Wageningen University:

International activities