Top Banner
Transitions to more sustainable urban water management and water supply Rutger de Graaf April, 2005 Expansion valve Water is pumped from the lake to the heat pump. Ground loop releases heat to cool earth In the cold zone, the working fluid absorbs heat from circulating lake water. Hot working fluid in the coil, releases heat to the closed ground loop. Cooled lake water is released again to the lake to decrease water temperature. Compressor Pump Sun provides heat to the surface water
178

Transitions to more sustainable urban water management and ...

Jan 13, 2022

Download

Documents

Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Microsoft Word - Final Report Transitions SUW.docwater supply
Expansion valve
Water is pumped from the lake to the heat pump.
Ground loop releases heat to cool earth
In the cold zone, the working fluid absorbs heat from circulating lake water.
Hot working fluid in the coil, releases heat to the closed ground loop.
Cooled lake water is released again to the lake to decrease water temperature.
Compressor
Pump
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 2
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 3
water supply
Report nr. 1.2005
Delft University of Technology Faculty of Civil Engineering and Geosciences
Section of Water Resources Stevinweg 1
2600 GA Delft
Graduation Committee Dr. ir. F.H.M. van de Ven - Delft University of Technology Prof. dr. ir. N.C. van de Giesen - Delft University of Technology Prof. ir. F.H.L.R. Clemens - Delft University of Technology Drs. P.J.A. Baan - WL|Delft Hydraulics Drs. R. van der Brugge - Erasmus University Rotterdam Drs. P.L.G.M. Hesen - Kiwa Water Research Drs. D. Loorbach - Erasmus University Rotterdam
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 4
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 5
Preface This MSc thesis report is an exploration and feasibility study to future urban water systems. In this report two future water systems are elaborated and the feasibility of these water systems is determined. The preparation of this report has been a long and interesting project that would not have been possible without the help of encouragement of my family, friends and supervisors. I would like to thank the following people in particular for their contributions: my supervisor Frans van de Ven for his encouragement, enthusiasm and clear vision on water management. The other members of the graduation committee Paul Baan, Peter Hesen, François Clemens and Nick van de Giesen for their constructive criticism and valuable remarks and suggestions. Rutger van der Brugge and Derk Loorbach, for teaching me about transitions and watch over the societal component of my report. And last but certainly not least, my girlfriend Anna van Dinther for being there and for listening to my stories about this graduation project. Rutger de Graaf April, 2005
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 6
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 7
Summary Introduction The current state of the urban water system and urban water supply is the result of ages of measures, which have resulted from societal demands of the past. Urban water management supports a wide range of functions and needs. As a result, various interests such as ecology, public health, safety and economy should be balanced in the design of an urban water system. In this report concepts for future urban water systems are developed. For this purpose, first an analysis has been made of the needs and functions of urban water systems. Subsequently, problems, threats and opportunities have been studied and the system lay out has been analysed. Moreover, this report contains an analysis of the regime of organisations, to indicate actors and importance of actors. Besides, a vision has been extracted from the most important policy documents, technology developments, autonomous trends and needs. The feasibility of two future water systems, the Closed City and the Two Layer City has been studied as well as the implications of these systems for organisations. At last, obstacles for realization of future water systems have been indicated and both concepts have been evaluated. Transition process In urban water management, there is no agreement about the problem and the solution. Moreover, urban water management is characterized by a variety of interests, which may conflict with each other. Consequently, technical optimisation only, does not lead to the desired objective. In such a situation another approach is required, the transition approach is an example of such an approach. The transition approach is an approach, which describes broad societal changes and the mutual relations and complexity of these changes. A transition is a structural change in the way a societal system operates. A transition is a long-term process (25-50 years). Such a transition process in water management is already taking place and is focused on more sustainable and integrated water management. This transition process can be recognized by new approaches such as, ‘Room for rivers’, ‘Water as guiding principle’ and the retain-store-discharge principle. The transition process in water management is currently in the take off phase. In order to shape the transition process, objectives and ideas for a future sustainable water system are needed. In this thesis technically feasible future urban water systems are described, which can play a role in developing transition paths. Problem exploration For the transition process, in this report research has been conducted to find out if it is possible to make use of the following opportunities.
Available water may be used more efficiently, while the water system still contributes to public health, environmental and ecological quality and the living environment. An example is the use of runoff for useful purposes such as groundwater and surface water storage. In particular at places where urban water supply leads to groundwater depletion in surrounding areas, it would be an advantage if local water resources were used more efficiently.
Use of materials, energy and space may be decreased if local water resources are used more efficiently, for instance, the required dimensions of sewer systems become smaller if rainwater is no longer transported by the sewer system. Moreover, less dilution of wastewater takes place.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 8
A better balance between rainfall, storage and water shortage may be achieved by retaining and storing water within the city borders, for instance by infiltration facilities.
Groundwater and surface water levels may be adapted to prevent rotting of pile foundations, flooding of cellars and balance water surplus and water shortage.
Problem statement
Can urban water systems in the future be a feasible and more sustainable alternative for the present urban water systems?
Are future urban water systems (1) technically feasible (2) socially feasible and (3) preferable above current urban water systems?
Demands and needs The most important demands on urban water systems are sustainability, safety, housing conditions, public health, ecological quality and a high quality living environment. To balance these needs sustainability can be defined in a broad sense which consists of social, economic and ecological components. These components of sustainability can be subdivided further in the following objectives for future water systems. Future generations
Sustainable use of water Sustainable use of energy Sustainable use of space
Economic aspects Economic sustainability
Ecological aspects Clean water Varied morphology of water system Self-supporting system Connections with other ecosystems
Present generation
Reliable, clean and healthy water supply Reliable system to collect and transport wastewater Reduce water nuisance High quality living environment
The components of sustainability have been used to systematically analyse problems, threats and opportunities. These can be used to define a vision on urban water systems. There appear to be four influence fields on vision development, these are society, policy, technology and autonomous trends. If these are brought together, a ideal future water system could be defined as a water system that focuses on solving problems at a local scale, provides good surface water and groundwater quality, offers good possibilities for nature, secures public health, saves water and energy and is flexible for autonomous trends. Consequently, two future water systems can be defined. The first is the Closed City. The Closed City is a city that does not have adverse effects on its surroundings, such as water depletion or emission of pollution. The Closed City uses local rainfall as the only source for water use, improves water quality by self-purification processes and copes with water nuisance at a local scale. The second future water system that has been
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 9
developed is the Two Layer City. The Two Layer City is a city that makes use of the water system to save energy. The Closed City The feasibility of the Closed City in average Dutch circumstances has been studied for three components, namely water quantity, water quality and water nuisance. The conclusion of the feasibility study is that the Closed City is technically feasible. For water quantity the ‘One house city schematisation’ has been developed, which, together with the water system analysis, is the base for a water quantity model. Results from this model show that local rainfall can compensate water use in a new residential district. However, there are a number of conditions. At first, the housing density should be low. At second, most rainfall should be kept in the urban water system, as a result, the stormwater infiltration or disconnection percentage should be high. To secure water supply during dry years, a part of effluent from wastewater treatment plants should be discharged back to the urban water system during dry spells. Another possibility is management of water demand by demand management measures, for instance the use of water saving technology, water pricing or public campaigns. Use of water saving technology only, can already decrease water use with 20%. This amount increases the feasibility and robustness of the Closed City to a large extent. Discharging effluent back to the urban water system is possible, although there are strict conditions. The possibility to discharge effluent back to the urban water system is a water quality issue; concentrations of oxygen, nitrogen, phosphorus and heavy metals must comply with water quality standards. For this purpose water quality calculations have been made to determine the effect of effluent on surface water quality. It appears that discharging effluent back is possible, although natural and artificial purification processes should be improved considerably. The nutrients removal efficiency of wastewater treatment plants should be increased as well as the efficiency of runoff purification processes, for instance by making use of infiltration, settling basins or reed bed filters. Moreover, the self-purifying capacity of the urban water system should be increased by circulation and adjusted morphology, for example by applying vegetation in canals and adjusting side slopes. Moreover, the oxygen demand of the bed sediments should be low, because it appears that the internal waste load has a determining influence on water quality. It is possible to cope with water nuisance locally without shifting problems to surrounding areas. The amount of storage, which has to be installed to cope with water nuisance problem can be realised in various ways, for instance by constructing an inundation area percentage of 15% combined with 500 mm allowable water level fluctuation. The inundation area consists of both surface water and area that is suitable for inundation such as parks. The water level fluctuation must be realized in addition to the seasonal fluctuation. Such a level fluctuation is only possible if the built environment is adjusted to this fluctuation. Because groundwater levels will fluctuate a lot, houses and other buildings should be able to cope with this. Another important aspect is the runoff collection system. This system should be able to collect and transport runoff effectively. In the Closed City, a surface runoff collection system is used combined with a wadi system. The combination of these systems offers good possibilities for purification of runoff and to keep water within the water system, which is needed for water use purposes. Some pumping capacity will be needed and consequently some water will discharge to the surrounding areas, however, because of its large storage capacity the Closed City has also the ability to accommodate water nuisance problems from surrounding areas. By installing a small pumping capacity in the Closed City, adjacent water systems and the Closed City can have mutual advantage by shifting problems on purpose to the place where it causes no problems. Other measures have also been evaluated. Increasing overland flow length, using permeable pavements and green rooftops lead to a larger time of concentration and consequently to smaller
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 10
dimensions of the runoff collection system. However, these measures are not useful to decrease the required amount of storage in the Closed City. The Closed City is all about managing fluctuations and adjusting the city to these fluctuations. By varying level differences and drainage capacity according to the function of the urban area, water nuisance can be managed and a resilient urban water system can be designed. Adjusted building technology plays a crucial role to achieve such a water system and make groundwater and surface water fluctuation possible. The Two Layer City In the Two Layer City, groundwater heat pumps are used to supply heat to houses. Consequently, less conventional energy is needed. Groundwater is a very suitable heat source because it is a lowly valued energy source, thus it cannot be used for other purposes than heating. Contrarily, conventional energy sources such as gas or electricity are highly valued energy sources because a large amount of these energy sources can be converted into work. Therefore, these sources are suitable for other more useful purposes. From the viewpoint of efficiency, it is preferable to use groundwater for heating of houses. Very high efficiencies can be achieved, up to 400% of the electrical input is supplied as heat to the building, which is a much better efficiency than the conventional central heating systems. Energy use of houses can be decreased about 50% if heat pumps are applied. Heat pumps can be applied nearly everywhere in the Netherlands, however in less suitable circumstances, larger ground loops are required and consequently costs are higher. Less suitable circumstances are for instance, soils with a low thermal conductivity or a very low groundwater table. Extracting heat from surface water in summer, storing it in groundwater and extracting this heat in winter to heat houses, is possible and provides about 40% of the total residential room heating demand. Extracting large amounts of heat from aquifers leads to a structural decrease of groundwater temperature, especially if many buildings within a relatively small area make use of heat pumps. A decrease of temperature of an aquifer is undesirable from an ecological point of view and because effects of such a decrease are still uncertain. Integration with the surface water system provides a source of heat to reload the aquifer. In urban areas the air temperature and surface water temperature are about 1.5 oC higher, in summer the high water temperature leads to problems, for instance, algae bloom, anaerobic conditions and turbidity. Cooling the surface water to 19oC during August and July has a beneficial influence on the water quality and can provide heat to the aquifer. Heat balance calculations show that this amount is almost 40% of the total heat demand for room heating of houses. The heat pumps operation energy is added to this amount as well as the heat flow that results from cooling houses in summer. Deeper groundwater layers and the surface should supply the remaining part of the required heat. Implications If future urban water systems would be realized in practice, there would be a number of implications for involved organisations and inhabitants. First of all, water chain and water system are integrated in the Closed City, the urban groundwater and surface water are the source for the urban drinking water supply. Consequently, there are more dependencies between the municipality, the water board and the drinking water company. Expected obstacles are the distribution of costs and responsibilities. Consequently, more cooperation is required between the involved organisations in the Closed City. Also the formation of one water organisation that is responsible for all water tasks such as, water quantity management, water quality management, runoff collection, sewer system, waste water treatment and drinking water supply could be an alternative. The Closed City will involve inhabitants more because inhabitants experience their drinking water supply in their own living area and have influence on their drinking water supply. This asks for responsible behaviour, more involvement and managing of risks. More knowledge
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 11
is required for these aspects because failure on these points could be a major obstacle for the realization of the Closed City. The Two Layer City results in integration of water system and energy supply. Therefore, organisations, which used to have no relation, will now have to cooperate. By integrating the energy supply with the water system, the water board, being the manager of the water system, gets involved in the energy supply. Heat from surface water is extracted in summer, stored in an aquifer and extracted in winter. Consequently, cooperation between the water board and the energy supplier is needed. Another possibility is a situation where the water board takes up the responsibility to supply heat to households in the city, or even the situation where the inhabitants themselves are responsible for their individual groundwater heat supply. Obstacles for the realization of future water systems are the costs that are probably higher and the fact that not all effects, both positive and negative, of future water systems are known and quantified. Evaluation To evaluate future water systems an assessment has been made on the general feasibility of these systems. General feasibility includes technical feasibility, effectiveness, costs, desirability, preferability and contribution to sustainable development. Both alternatives contribute to sustainability in a positive way by reducing use of energy and materials, improving water quality and efficient water use of scarce water. The Closed City reduces external water supply almost entirely, whereas the Two Layer City provides about 50% of the total room heating demand of a residential district by extracting heat from surface water. Moreover, both future water systems use space for multiple functions. The preferability of the future water systems cannot yet been determined because information about costs and relevant effects is still lacking. Therefore, more research is needed and these innovations should be protected and developed further in applications. If technology proceeds and risks can be managed, future water systems can be preferable in the future.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 12
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 13
1.1 The importance of water.................................................................................................26
1.3 Needs for sustainability...................................................................................................26
1.6 A high quality living environment .................................................................................29
1.7 A healthy ecosystem ........................................................................................................29
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 14
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 15
5.1 The city system approach ...............................................................................................75
5.2 A vision as a result of four influence fields....................................................................76
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 16
5.3 Two future water systems...............................................................................................78
6.1 Ideas for Closed City Concepts ......................................................................................79
6.2 Water quantity analysis ..................................................................................................82 6.2.1 Schematisation of a new housing district......................................................................82 6.2.2 Schematisation of the water system ..............................................................................83 6.2.3 Water quantity model....................................................................................................84 6.2.4 Calculation of flows ......................................................................................................85 6.2.5 Water quantity assessment for several circumstances...................................................92 6.2.6 Influence of design parameters on water availability....................................................96 6.2.7 Sensitivity analysis........................................................................................................99 6.2.8 Demand management..................................................................................................100
7.1 Energy conservation......................................................................................................135 7.1.1 How a heat pump works..............................................................................................136 7.1.2 Types of groundwater heat pump systems ..................................................................137 7.1.3 Efficiency of heat pumps ............................................................................................138 7.1.4 Working fluids ............................................................................................................139 7.1.5 Heat pumps for residential use....................................................................................139 7.1.6 Applicability of groundwater heat pumps...................................................................140 7.1.7 System response of groundwater ................................................................................141
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 17
8.1 Implications of the Closed City ....................................................................................152 8.1.1 Implications for organisations.....................................................................................152 8.1.2 Implications for inhabitants.........................................................................................154 8.1.3 Obstacles and advice for realization of the Closed City .............................................154
9.1 Contribution to sustainable development ...................................................................157
9.2 Effectiveness...................................................................................................................158
APPENDIX C: INPUT VALUES FOR OXYGEN DEFICIT CALCULATION.................178
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 18
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 19
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 20
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 21
Introduction Current situation The current state of the urban water system and urban water supply is the result of ages of measures, which have resulted from societal demands of the past. Urban water management support a wide range of functions and needs, as will be discussed in the next chapters. As a result, various interests such as ecology, public health, safety and economy should be balanced in the design of an urban water system. As different opinions exist about the importance of needs and functions of these systems, there is no agreement about what the ideal urban water system should look like. However, there is agreement about the fact that until recently, most water systems has been focused on mainly technical measures and that other aspects such as ecology and living quality are now regarded as being more important than they used to be. Consequently, a new balance should be found between demands on water systems. For this purpose knowledge is required about which concepts can be realized and which cannot be realized. Therefore, in this report research will be conducted to find out if it is possible to make use of the following opportunities.
Available water may be used more efficiently, while the water system still contributes to public health, environmental and ecological quality and the living environment. An example is the use of runoff for useful purposes such as groundwater and surface water storage. In particular at places where urban water supply leads to groundwater depletion in surrounding areas, it would be an advantage if local water resources were used more efficiently.
Use of materials, energy and space may be decreased if local water resources are used more efficiently, for instance, the required dimensions of sewer systems become smaller if rainwater is no longer transported by the sewer system. Moreover, less dilution of wastewater takes place.
A better balance between rainfall, storage and water shortage may be achieved by retaining and storing water within the city borders, for instance by infiltration facilities.
Groundwater and surface water levels may be adapted to prevent rotting of pile foundations, flooding of cellars and balance water surplus and water shortage.
Figure 0-1: Flooding in Delft in 2002 (Min van V&W, 2003)
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 22
Developments The following relevant developments can be distinguished, which should be taking into account if a new water system is designed:
Climate change The climate of the Netherlands, will probably face dramatic changes in the coming decades. These changes will result in wetter winters, drier summers, higher intensity rainfall and a rising sea level. (WB21, 2000) Land subsidence The Netherlands has been shaped by the battle against water. Building dikes and polders have protected the low-lying parts against flooding from rivers and sea. However, the continuing pumping, drainage and cultivation of these areas has resulted in an ongoing process of subsidence. This process combined with the sea level rise has already led to the fact that a large part of the country is situated below the sea level, protected by dikes against rivers, canals and the sea, which are situated higher. In the future land-subsidence will continue if the management remains unchanged. Changing needs from society
Urban water is no longer considered as a single purpose element, which supports water quantity functions only. The main function of urban surface water was to store rainwater. However, today urban surface water also has to support ecology and recreation and urban surface water plays a role in the urban design as well. The demands of the urban surface water and groundwater have changed in terms of quality, quantity and the need for space.
Classification of the water management problem The water management problem, which is indicated above, is a so-called persistent problem. (Rotmans et al, 2003) Persistent problems are types of societal problems that have the following characteristics:
Significant complexity Structural uncertainty High stakes for a diversity of stakeholders involved Deeply rooted in our societal structures and institutions
It can be concluded that urban water management issues satisfy the description of a persistent problem; because of the many functions and forms of urban water (groundwater, surface water and drinking water), the uncertainty of: future needs, technologies and developments, climate change, knowledge of the water system and the diversity of stakeholders (waterboards, municipalities, other institutions and water users). Furthermore, these institutions make large investments in the urban infrastructure. Transition process In case of persistent problems, there is no agreement about the problem or the solution. Moreover, these problems are characterized by a variety of interests, which may conflict with each other. Consequently, technical optimisation only, does not lead to the desired objective. In such a situation another approach is required, the transition approach is an example of such an approach. A transition is a structural change in the way a societal system operates. A transition is a long- term process (25-50 years) which is characterized by four phases and three levels. (See Rotmans
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 23
et al, 2003). Figure 0-2 and Figure 0-3 show the concept of transitions. Such a transition process in water management is already taking place and is focused on more sustainable and integrated water management. This transition process can be recognized by new approaches such as, ‘Room for rivers’, ‘Water as guiding principle’ and the retain-store-discharge principle. The transition process in water management is currently in the take off phase. (Van der Brugge, Loorbach and Rotmans, 2003) Figure 0-2: Four phases in the transition process (Rotmans et al, 2002)
Figure 0-3: Interaction between different scale-levels (Geels and Kemp, 2000).
Time
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 24
Function of this thesis in the transition process In order to shape the transition process, objectives and ideas for a future sustainable water system are needed. In this thesis technically feasible future urban water systems are described, which can play a role in developing transition paths. Objectives for a future urban water system What should a future urban water system look like? The following objectives, which are related to sustainable development, are desirable for a future urban water system:
Socially sustainable for future generations, which means that we should use space, energy materials and water in a sustainable way.
Socially sustainable for present generation. For the present generation, a reliable, clean and healthy water supply is important; moreover, also a system to collect and transport wastewater should be present. Besides, the frequency of water nuisance should be limited to an acceptable frequency and the quality of the living environment should be high.
Economic sustainable. The future water system should be economic feasible (costs, opportunities for companies and jobs).
Ecologically sustainable. A system is ecologically sustainable if the water is clean, the morphology of the water system has a lot of variations, the system is self-supporting and there are connections with other ecosystems.
Problem statement
Can urban water systems in the future be a feasible and more sustainable alternative for the present urban water systems?
Are future urban water systems (1) technically feasible (2) socially feasible and (3) preferable above current urban water systems?
General objective The development of technologically feasible and inspiring concepts of future sustainable urban water systems. Reading guide In this report concepts for future urban water systems are developed. For this purpose, in chapter 1 analysis is made of the needs and demands of urban water systems. In chapter 2 the many functions of surface water, groundwater, drinking water and rainwater are summarized. Subsequently, problems, threats and opportunities are studied in chapter 3 and the system lay out is analysed in chapter 4. Moreover, this chapter contains an analysis of the regime, to indicate actors and importance of actors. In chapter 5 a vision has been extracted from the most important policy documents, technology developments, autonomous trends and needs. The feasibility of two future water systems, the Closed City and the Two Layer City is studied in chapter 6 and chapter 7. Chapter 8 presents the implications of these systems for organisations. At last, obstacles for realization of future water systems are outlined in chapter 9. The busy reader, who wants to read more than the summary only, is recommended to read the introduction, take a quick glance at chapter 3, read chapter 5 and the concluding paragraphs of chapter 6 and 7 as well as the conclusions and recommendations chapter.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 25
Structure of the report
Phase in research Results
1. Demands on urban water systems Needs and demands of watersystems
2. Function analysis Overview of functions of urban water 3. Problem analysis Problems and objectives
4. System analysis Overview of natural, socio-economic and administative system
5. A vision on future urban watersystems Development of a vision
6&7. Future water systems Ideas and feasibility for future urban water systems
8. Implications of future watersystems Implications for organisations and inhabitants
9. Evaluation of future water systems General feasibility
10. Conclusions and recommendations Concluding remarks and suggestions for further research
Figure 0-4: Structure and results of the report
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 26
1 Demands on urban water systems Purpose and scope of this chapter As a starting point for this study on sustainable urban water management first is evaluated why water is important and which needs should be fulfilled by an urban water system. Finally, water management policy will be elaborated.
1.1 The importance of water The importance of water is very obvious and yet often so obvious that it is forgotten or that important aspects of the importance of water are overlooked. The first reason why water is important is that humans consists for about two thirds of water and that life without water is –as far as we know- impossible. Explorations to Mars are always focused on finding water or traces of water from the past, because a sign of water perhaps means a sign of life. Water has also a strong cultural value, ancient cultures such as the Egyptian and Roman culture all started near rivers. Moreover, rivers often play a major role in a national identity and also in religion and literature, songs and paintings. Water attracts people and even today a great percentage of the world population is situated near rivers and coasts. Just over half the world's population - around 3.2 billion people - occupy a coastal strip 200 kilometers wide, representing only 10 per cent of the earth's land surface. (peopleandplanet, 2004) In her anthropological study ‘the meaning of water’ Veronica Strang reflects on how deep water is anchored in human conscience and how it stands for wealth, power and connections with others. As will be evaluated in the next chapter, water support an enormous range of functions; households, industry, transport, recreation, ecology, food production, waste water discharge etc. It is for all these reasons that water is important and in the next paragraph, management of this resource will be treated
1.2 Overall aim of water management The overall aim of water management according to the 4th National Policy Document on Watermanagement is:
‘To have and maintain a safe and habitable country and to develop and maintain healthy and resilient water systems which will continue to guarantee sustainable use.’
It is clear that both the needs of people (Safe and habitable country) and the ecosystem (Healthy and resilient water systems) are given attention in the general objective, although a healthy and resilient water system certainly also benefits the needs of people. A safe and habitable country with regard to urban areas means: no water nuisance from groundwater, surface water and rainfall. The different between nuisance and flooding is made because a wrongly designed or managed urban water system can result in nuisance (water in cellars and crawlspaces) but not in flooding, because flooding is caused by the collapse of river dikes or sea dikes. Sustainability is an important element in the overall aim of water management therefore, first will be evaluated what sustainability is.
1.3 Needs for sustainability Since the publication of the UN report ‘Our common future’ of the Brundtland commission in 1987, sustainability as attracted massive attention from researchers from around the world. The central idea of sustainability is considered primarily in terms of continuing to improve human
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 27
well being, whilst not undermining the natural resource base on which future generations will have to depend. Sustainability can be used in various ways and there are several definitions of sustainability all with their differences and similarities. There is no common agreement on the exact definition of sustainability. Four key-elements can be extracted from the most common definitions. (Rijsberman, 1999)
To cover the needs of the present generation To cover the needs of the future generations To preserve the elements of the system To preserve system integrity
The future needs are hard to determine, yet these needs shape the possible future functions, which are required in order to know which measures are promising. The systems and sub-systems of the urban environment should have sufficient quality and quantity to fulfil their function in the future as well. However, it is very difficult to estimate what ‘sufficient’ is. For some functions this is easier than for others, what is for instance sufficient water quality for recreation? And is sufficient good enough or should we strive for the best possible water quality we can achieve? System integrity should be preserved because system elements and the relation between these elements determine the achievements of a system. It does not necessarily mean that the system should stay the same; as a result of a transition, functions can also be realized in another way or perhaps disappear. The importance of system integrity lies in the fact that all the parts of a system may function well, but the system as a whole does not. Therefore, it is essential to take the relations between system elements into account. Sustainability implies often the conservation of resources; the use of renewable resources may not be higher than the speed of regeneration. Non-renewable resources may not be depleted before alternatives have been found. (Mostert, 1998) The definition of sustainability also means that a deterioration of water quality that threats the functions of urban water is not acceptable. Rotmans et al. (2001) give the following integrative approach towards sustainability.
1. Consider the dynamic development on a timescale of 25-50 years 2. Consider the spatial development on at least two scales: micro and macro scale 3. Make a distinction in sustainable social, economic and ecological development,
and try to analyse the coherence This approach can be expressed in triangle model, which has been developed by ICIS and symbolizes three domains of sustainability and their mutual relations. The three domains are the social, economic and ecological capital. Water related examples of social capital are: flooding safety and public health; economic capital is for instance: water, which can be used for economic production, such as agriculture, energy supply etc. Ecological capital can be expressed in biodiversity and quality living environment. In a sustainable approach there should be a balance between the three domains and development of one domain should not harm the other domains. For instance, economic development should not have adverse effects on the ecological and social capital. In practice, however, this is often the case. In the figure the social capital is the top of the triangle, at the left corner is the ecological capital, whereas the economic capital is at the right corner.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 28
Figure 1-1: ICIS triangle with three domains of sustainability (Rotmans, 1998) How does sustainability relate to the general objective of water management? People and ecosystems make various demands on the urban water system. These needs lead to a range of water related functions that will be investigated later in the report. As we will see, these functions and needs can conflict with each other.
1.4 Safe and habitable country Besides sustainable use, one of the main components of the aim of water management is to develop and maintain a safe and habitable country. To make the country habitable automatically means human interference in the natural water system, at least in large parts of the Netherlands. Dikes protect more than half of the country against flooding and water management is needed for any form of development in these areas. Therefore, water systems in the Netherlands are mostly artificial systems. However, also within these artificial systems one can maximize the opportunities for ecosystems and also within these artificial systems, natural processes can be used to obtain a more sustainable water system. The fact that people do not want water nuisance in their living area, makes demands on the drainage and storage functions of the water system. If these are designed properly no frequent nuisance will occur. However, the buildings can be adjusted to fluctuating water levels to limit water related damage as well. For economic reasons a low frequency of nuisance is accepted, because it is very expensive to prevent nuisance completely. Therefore a certain return period of water nuisance is selected and the design of the drainage and storage is based upon this return period.
Figure 1-2: Houses for handling fluctuating water levels in Maasbommel (Min van V&W, 2000)
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 29
1.5 Needs for public health The needs of society with regard to the water chain are mainly related to health and comfort. The water chain consists of: drinking water treatment-distribution-water use-sewerage-wastewater treatment and discharge. In the figure below, the position of the water chain in the hydrological cycle has been indicated. A clean and reliable water supply is essential for public health. Besides, safe transport of wastewater out of the direct living environment is provided by the sewer system. These two elements of the water chain, water supply and sewage system make high living conditions in urban areas possible. Clean water is used for drinking, cooking and washing; these are all activities with a beneficial influence on health. Besides, water supply also makes comfort in houses possible as it is used for showering and bathing. The standards for drinking water quality can be found in the drinking water law (waterleidingbesluit).
Figure 1-3: The waterchain in the hydrological cycle (DWI, 2004)
1.6 A high quality living environment Preventing water nuisance is not the only goal of the general aim of water management in the Netherlands. After all, absence of water nuisance does not automatically mean that there is a high quality living environment for housing, working and recreation. To fulfil this need, good water quality without stench, algae bloom and turbidity is essential. Besides, the urban water should be visually attractive, well designed, and accessible for inhabitants, it has to fit well in the urban landscape and contribute to the quality of the urban landscape and to the cultural value of a city.
1.7 A healthy ecosystem In the general aim of water management one of the main objectives is the maintenance and development of healthy and resilient water systems. This part is especially relevant for ecosystems. In urban areas a healthy water system means a water system, which is clean, for instance a water system that has a water quality that complies with the standards that have been stated in The 4th Water Policy Document. Resilient means that the water system has a high self- cleaning capacity and is as much self-supporting as possible. Human interference to maintain the
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 30
quality of the water system should be as low as possible. With regard to water quantity, a resilient system also means a self-supporting system, which retains and stores water as much as possible. Consequently, fewer water supplies from the surrounding area are needed and water nuisance is reduced by the storage capacity. The ecological quality of urban water systems should be as good as possible, it means that a large variety of species have opportunities to sustain and develop in the urban environment. This requires the following features for urban water systems: good water quality, a varied morphology of the water system that offers living possibilities for several species and the connection to other systems to offer species possibilities for migration.
1.8 Balancing needs A good ecological quality can benefit the living environment and therefore ecological and human functions can have mutual benefits. However, also the opposite is possible, for instance because ecological functions of an area can lead to restrictions for recreational use of that area. A water system should also be economic feasible, a ecologically very healthy water system can not be realized if the costs are extraordinary high; again it is about the balance between three domains of sustainability (economic, ecological and social). This balance is dynamic, which means that the qualities and quantities of the sustainability components may change. Which balance is sustainable depends on the context of the situation and to which extent the demands on the water system are fulfilled.
1.9 Water management policy There is both national and European policy with regard to water management. These two forms of water management will be further elaborated.
1.9.1 National policy Next to the 4th Policy Document On Watermanagement, which has been mentioned before in this chapter, there is also another relevant policy document of the national government. In the policy document “A different approach to water, water management policy in the 21th century” the government vision on water management has been outlined. The following elements are most important:
Anticipating instead of reacting on water More space for water in addition to technological measures Not passing on of responsibilities and problems
In the policy document a tool is described, namely, the water test. This tool has to ensure that water is taken into account in spatial plans. Moreover, space, which is needed for flood and prevention of water-related problems, may not be lost by use of other functions. A principle in the policy document is the retain-store-discharge principle, which has to prevent the passing on of problems. Areas themselves are responsible to accommodate water and may not cause water problems for their neighbours by discharging it to the surrounding areas.
1.9.2 European policy Next to national policy, there is European policy as well. The most important example is the European Water Framework Directive. The Framework directive has the following objectives:
To prevent deterioration and improve the status of aquatic ecosystems and dependent terrestrial ecosystems
To promote sustainable use of water
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 31
To decrease the disposal of priority substances and to stop the disposal of priority hazardous substances
To prevent further contamination of groundwater Source: (Mostert (2004) translation by author of this report) Surface water The Framework Directive demands a good status for all waters by 2015, for surface water there are two components "good ecological status" and "good chemical status". Good ecological status is defined in terms of the quality of the biological community, the hydrological characteristics and the chemical characteristics. Good chemical status is defined in terms of compliance with all the quality standards established for chemical substances at European level (EU, 2004). Groundwater The case of groundwater is somewhat different, for groundwater quality it comprises a prohibition on direct discharges to groundwater, and a requirement to monitor groundwater bodies so as to detect changes in chemical composition, and to reverse any antropogenically induced upward pollution trend. Taken together, these should ensure the protection of groundwater from all contamination, according to the principle of minimum anthropogenic impact (EU, 2004). The quantitative status is important as well. There is only a certain amount of recharge into a groundwater each year, and of this recharge, some is needed to support connected ecosystems. For good management, only that portion of the overall recharge, which is not needed by the ecosystem can be abstracted (EU, 2004). Type of water bodies The general description and goals, which were outlined in the former paragraphs, should be applied to various water bodies. It must first be determined whether a water system is ‘in a natural state’ or has been ‘dramatically changed’. In theory, the most ambitious ecological targets apply to ‘natural’ water systems. For water systems that have been ‘dramatically changed’, less ambitious targets can be established. However, governments are accountable to the European Commission for this and must explain their reasons for lowering the targets (e.g. public feasibility and disproportionately high costs. (Water in Beeld, 2004) Measures and the river basin management plan To reach ‘a good status for all waters by 2015’ for each river basin a so-called river basin management plan must be made to coordinate measures in that particulate river basin. This plan must be updated every six years. The hydrological unit, the river basin, is the starting point for the planning of measures, instead of an administrative or regional unit. In the Netherlands there are four international river basins, namely: the Rhine, Meuse, Scheldt and Ems. Public participation and water pricing Two other important elements of the Framework directive are public participation and water pricing. Public participation is important because an integrative approach requires balancing of interests and the Framework directive desires a transparent decision making process. For public participation, in the Netherlands, regional response groups have been established. Adequate water pricing acts as an incentive for the sustainable use of water resources and thus helps to achieve the environmental objectives under the Directive. Member States will be required to ensure that the price charged to water consumers - such as for the abstraction and distribution of fresh water and the collection and treatment of waste water - reflects the true costs. (EU, 2004)
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 32
2 Function Analysis Purpose and scope of this chapter In the former chapter the importance of water and a sustainable approach were evaluated. In this chapter attention an overview will be presented of the many functions of urban water. The results are required to be able to accomplish an integrative approach, which takes into account all relevant aspects. The place and function of this chapter are indicated in the following figure.
Phase in research Results
1. Demands on urban water systems Needs and demands of watersystems
2. Function analysis Overview of functions of urban water 3. Problem analysis Problems and objectives
4. System analysis Overview of natural, socio-economic and administative system
5. A vision on future urban watersystems Development of a vision
6&7. Future water systems Ideas and feasibility for future urban water systems
8. Implications of future watersystems Implications for organisations and inhabitants
9. Evaluation of future water systems General feasibility
10. Conclusions and recommendations Concluding remarks and suggestions for further research
Figure 2-1: Phase and results of chapter 2 In urban areas water appears in a number of forms, for instance surface water, groundwater, rainwater, wastewater and drinking water. These forms of water support several functions within the urban area and these functions make demands on the urban water in terms of quantity, quality and requirement of space. In this chapter the functions of the urban water will be examined.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 33
2.1 Surface water The urban surface water supports the following functions (Van de Ven, 2004): Table 2-1: Functions of the urban surface water
Water quantity functions
Water quality functions
Retain pollutants Landscape
2.1.1 Water quantity functions Three water quantity functions can be distinguished within the urban water system:
Storage Discharge Water supply
In most cases water quantity functions have been combined in water systems in the Netherlands. Especially in the lower parts in the west of the country this is case, because there is no sufficient difference in terrain height to have separate water supply and drainage systems. In the typically Dutch polder system one will find all three functions: supply, discharge and storage combined in the belt channel of the polder. The importance of discharge and storage is to prevent water nuisance and damage. These effects can result from high water levels, high ground water levels or the lack of capacity to discharge runoff. To prevent damage and nuisance, the capacity of storage and discharge has to be sufficient. The general goal is to limit certain water levels to acceptable frequencies and therefore to limit societal damage. The importance of water supply to the urban area is mainly related to other functions such as nature and social functions. However, it is related to groundwater functions as well; these functions will be discussed later in this chapter. In temperate areas in which the precipitation exceeds evaporation, water discharge has generally more importance than the water supply. However, in dry periods water supply to the urban surface water can be necessary to avoid low groundwater tables and ecological damage. Besides, water quality can make water supply necessary.
2.1.2 Water quality functions Besides water quantity functions the urban surface water also supports water quality functions. These functions are:
Degradation of pollutants
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 34
Transport of pollutants Retaining of pollutants.
Degradation of pollutants is important, due to the fact that there are many pollution sources in cities. Improvement of the degradation capacity of urban surface water, for example by water circulation or reed beds, has a positive impact on the water quality and therefore is favourable for lots of other functions. Pollution in urban areas either has to be broken down or transported out of the area. Therefore, transport of pollutants out of the urban area is a function of the surface water as well. Finally, the settling of pollutants has a beneficial effect on water quality. Settling of pollutants can take place in settling ponds and reed bed filters. In these facilities pollution can be broken down further or the pollution can be removed by maintenance of these facilities.
2.1.3 Nature functions To support nature, surface water is of great importance. This is the case for vegetation as well as for nature, in both aquatic and terrestrial ecosystems. The demands that ecology imposes on the water system are related to water quality, water regime (level fluctuations) and the morphology of the water system. In general the ecological quality of the water will be higher if the oxygen content is high, the amount of pollutants is low and there is variation in the water system, which offers various species possibilities. Banks with low gradient and level fluctuations are positive for ecological quality. Finally, connections with other ecosystems are essential to give wildlife the possibility to migrate to other areas.
2.1.4 Social functions Water has an important social function for recreation, culture and landscape. Recreation possibilities increase the quality of the urban living environment. The cultural function of water is important as well; the Netherlands is famous worldwide as water country; the windmills and canals attract many tourists each year. The battle against water shaped the country and water plays a key role in the urban landscape. Therefore, to maintain the cultural function of surface water it is necessary to conserve historical elements in the city which are related to water. Furthermore, it is important to minimize water nuisance such as inundations and stench. In new areas, water can also play a cultural role if it is integrated in the urban planning and people have access to surface water.
2.1.5 Other functions Other functions of urban surface water are separation and housing. To separate districts in cities, surface water can be used. A canal is able to separate parts functionally and visually. Houseboats can be found in many places as well as floating houses. The demands of this function for the urban surface water are sufficient water quality and visual quality. Also accessibility is important.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 35
2.2 Groundwater Groundwater has the following functions (Van de Ven, 2004): Table 2-2: Functions of the urban groundwater water
Water quantity functions
Water quality functions
Water supply Retain pollutants Reduction of weight
Groundwater supports a lot of functions in urban areas and at the same time the urban area has a large influence on groundwater. Moreover, groundwater in the unsaturated zone is essential for vegetation, because it is the water source for plants. Urbanisation leads to the construction of paved areas, which increases storm water flow and reduces evaporation. At the same time drinking water is pumped to the urban area and leakages occur. If the groundwater level is lower than the sewer level, leakages occur from the sewer system. If the groundwater level is higher than the sewer level, groundwater enters the sewer pipe, especially if the sewer system is old. The leakage of wastewater and various human activities cause pollution of the groundwater. The influence of the city on the groundwater is illustrated in figure 2.2.
Figure 2-2: The influence of the city on groundwater (Lerner, 2004, Barett et al. 1999)
2.2.1 Water quantity functions Groundwater has roughly the same water quantity functions as surface water, namely discharge, storage and supply. Also the objective of these functions is similar, namely to reach an acceptable risk level which is determined by a certain groundwater level combined with certain frequencies.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 36
The main difference between groundwater and surface water is the medium of flow; which is the reason for groundwater flow to be much slower than surface water flow. Groundwater has a storage function that can be useful, especially to cope with high precipitation intensities. In case of a phreatic water table, storage results in a climbing water table. In case of a confined aquifer it results in a higher piezometric head. Storage of peak rainfall in groundwater is quite effective because it slows down the runoff peak to a large extent and transforms high velocity stormwater flow to low velocity baseflow. By using infiltration, the runoff process gets closer to the process as it works before urbanisation takes place. However, infiltration of water is only possible if there are pervious surfaces or infiltration facilities and if a rise in groundwater level is allowable Excess of water can be discharged through canals and surface water but also through the groundwater. Eventually, groundwater ends up in surface water like canals, rivers or the sea. This can be done by natural processes or by means of drainage facilities which are constructed to maintain the groundwater table between certain limits. Drainage facilities can consist of drainage pipes, soil improvement or infiltration facilities with a draining function such as wadi systems. Various functions demand various groundwater tables; this can result in complications for multifunctional use of the urban space, because groundwater cannot easily be varied within a limited area. The optimal groundwater level is therefore the result of balancing of interests. A table that is too high can result in moist problems in cellars and crawl spaces, a groundwater table that is too low can result in land subsidence. Groundwater can be used to supply water during dry periods. Besides, groundwater plays a role in water supply through the process of seepage. This is especially the case in low level polders where the seepage flow can be very large. Another destination of groundwater supply is for industrial pumping stations. Industrial companies extract groundwater to use for cooling and cleaning purposes. However, sometimes industrial extraction is even needed to maintain a current groundwater table, for instance in Delft (DSM) and Eindhoven (Philips). In these situations, equilibrium has been reached by extraction; as a result, extraction has to be continued to prevent damage.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 37
Table 2-3: Demands on drainage depth and discharge for various functions (Van de Ven, 2004)
Activity/destination Steady drainage- computation
Drainage depth Design discharge
(m below ground level) (mm/24hrs) I. during the construction phase construction of structures 0.60- 0.70 laying of telephone-cables 0.50- 0.60
Low voltage cables 0.60 Gas lines 0.65- 1.00 High voltage cables 0.90 Sewer pipes 1.00- 3.50
construction of primary roads 1.00 secondary roads 0.70 squares, parking lots 0.40
accessibility 0.50-0.70 Summary: during the construction phase 0.70- 0.80 10 II. the habitation phase structures 0.70 cables and pipelines 0.60- 1.00 primary roads 1.00 secondary roads 0.70 industrial areas, centre areas 0.70 Summary: the habitation phase 0.70 5 Gardens, public gardens, parks 0.50 7 Camping areas 0.50 10 Graveyards 0.30 below underside coffin 10 Sport fields 0.50 15 Non-steady drainage computation 0.70 Drainage depth with frequency of
exceeding of 1 event per year
2.2.2 Water quality functions The water quality functions of groundwater are important, because groundwater can influence the surface water quality through seepage and affect drinking water wells. Moreover, groundwater can have an effect on public health as well if it causes moisture in houses. Human activities are a cause of groundwater pollution and because of the generally long residence time of groundwater, it can take years before effects are noticed. Pollution transport by groundwater takes place by advection and dispersion processes. Groundwater quality processes are mostly autonomous processes, which are hard to influence and, in case of dispersion, are irreversible. Therefore prevention of pollution is the best solution, also because soil cleaning is very costly. On the other hand, groundwater degradation processes can be used to purify water. A good example of this is artificial infiltration for drinking water production.
2.2.3 Foundation Groundwater has a large impact on the foundation of buildings. There are three foundation related functions of groundwater namely: Prevention of oxidation, reduction of subsidence and reduction of weight.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 38
Peat soils are very sensitive for oxidation; as soon as the peat is exposed to oxygen the oxidation process starts. This process can result in an enormous lowering of the terrain level. In many parts of the Netherlands this has taken place and the terrain level is meters lower than it used to be. Peat oxidation is practically irreversible as the formation of new peat layers takes hundreds of years. The oxidation of wooden piles is to be prevented as well, because piles that are exposed to oxygen will start rotting and rehabilitation of a foundation is very costly. Peat and pile oxidation can be prevented if the water level is kept close to the terrain level. However, other functions often ask for a lower groundwater table. Another problem that is related to groundwater is land subsidence, lowering of the groundwater table results in a higher grain stress, which result in land subsidence, this process is irreversible as well. A high water table decreases or prevents subsidence. Moreover, groundwater absorbs a part of the weight of structures; this property of groundwater is used in designing floating roads that make use of the bearing capacity of groundwater, also for this purpose, a high groundwater table is required.
2.2.4 Nature Vegetation in gardens in park depends on the subsoil moisture content, which is determined by the groundwater level and the soil type. In cities, green areas often have both an ecological and a recreational function. For these green areas, sometimes additional supply of water is needed and sometimes drainage is needed. Various ecosystems demand various groundwater tables; the type of ecosystem determines the desired groundwater regime. However, other functions have to be taken into account during this process. The method of determination of groundwater regimes based upon (ecological) functions as been described extensively in the method of the ‘project Waternood’ (see for instance: Runhaar, 2002). Ecosystems demand a certain water quality as well, which is determined by the type of ecosystem which has to be supported.
2.3 Drinking water For drinking water the following functions can be distinguished: Table 2-4: Functions of drinking water
Household water supply Industrial water supply Other Bath and shower Cleaning Firefighting Wash basin Cooling Irrigation Toilet flush Heating Horticulture Food preparation Production Dishwashing Cloth washing Drinking Cleaning
Garden
Pipe supplied drinking water is one of the most important sources of urban water. The functions of drinking water vary from household water supply to industrial supply and other purposes such as irrigation and fire fighting. Within the scope of this study, most attention will be given to
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 39
household purposes, whereas the other functions will be mentioned shortly. The main sources of drinking water are surface water and ground water. Additionally, water from dunes and water from riverbanks provide a part of the water supply. Table 2-5: Sources of drinking water in the Netherlands (Vewin, 2004)
Ground water Dune water Riverbank groundwater
Surface water
Total: 1,301
2.3.1 Household water supply An average daily amount of 126 litres of water is used by each citizen in the Netherlands. This water is used for various functions. The following table presents an overview for the situation in the Netherlands for the year 2001. Table 2-6: Average water use in the Netherlands in 2001 (Vewin, 2004)
Water use per time (l)
Use frequency per day
(l) %
Wash basin 4.0 1.30 100% 5.2 4%
Toilet flush 5.8 5.99 100% 34.8 27%
Cloth washing, hand 36.0 0.05 100% 1.8 1%
Cloth washing, machine 80.0 0.29 99% 22.8 19%
Dishwashing, hand 8.0 0.45 100% 3.6 3%
Dishwashing, machine 20.0 0.24 51% 2.4 2%
Food preparation 1.6 1%
Others 6.7 5%
Total 126.2 100%
Showering makes up for the biggest water use in the average household, followed by toilet flush and the washing machine. Water for all these purposes is of very high drinking water quality, whereas less than a half of the water use purposes needs this very high quality from the point of
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 40
direct health risks. (Van Dijk, 2002) From these purposes, showering uses a large part. Water to drink and food preparation only use 2% of the total water use. For toilet flushing, washing machines and others, such as watering the garden or washing the car, water of less quality could be used.
2.3.2 Industrial water supply Although industries often have their own water supply in the form of a groundwater pumping station also drinking water is being used for industrial processes such as heating or cooling. Industrial use of drinking water accounts for 14% of the total drinking water supply. (Vewin, 2000)
2.3.3 Other functions Other functions of drinking water are fire fighting and irrigation. Fire fighting is important for safety reasons and plays an essential role in the dimensioning of drinking water distribution systems. This is because the fire fighting discharge is mostly the critical demand, which determines the diameter of the pipes. However, in new design methods the influence of fire fighting demand is smaller than it used to be and the actual drinking water demand becomes dominant. (Vreeburg, 2004) The total amount of not charged water supply (leakages and fire fighting supply) was 5% in 2000 (Vewin, 2000). Also for the irrigation of public green spaces, drinking water is used.
2.4 Rainwater Rainwater has the following functions: Table 2-7: Functions of drinking water
Recharge Household water supply Surface water recharge Toilet flush Groundwater recharge Cloth washing
Figure 2-3: Groundwater and rainwater recharge by precipitation
2.4.1 Recharge Rainfall is an important source for both groundwater and surface water recharge. After interception, runoff and evaporation losses, water is added to the groundwater storage. By direct precipitation and runoff also surface water is refilled.
2.4.2 Household water supply For some of the household purposes rainwater can be used, for instance for cloth washing and toilet flushing. For this functions water of less quality could be used. However, as will be discussed in the next chapter, rainwater collection systems unfortunately have some disadvantages as well.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 41
3 Problem analysis Purpose and scope of this chapter The former chapter addressed the various functions of the urban water systems. This chapter on one hand investigates what the problems are in urban water management. On the other hand, the goal is to find objectives and criteria to develop future water systems and to be able to evaluate those future water systems. The following figure indicates the position and results of this chapter.
Phase in research Results
1. Demands on urban water systems Needs and demands of watersystems
2. Function analysis Overview of functions of urban water 3. Problem analysis Problems and objectives
4. System analysis Overview of natural, socio-economic and administative system
5. A vision on future urban watersystems Development of a vision
6&7. Future water systems Ideas and feasibility for future urban water systems
8. Implications of future watersystems Implications for organisations and inhabitants
9. Evaluation of future water systems General feasibility
10. Conclusions and recommendations Concluding remarks and suggestions for further research
Figure 3-1: Position in the report and results of chapter 3 If one or more functions are not supported sufficiently, one speaks of a problem. In other words: a problem is the difference between the desired and existing or expected situation. However, water management is not only about solving problems, also opportunities and challenges are important. In such a case the functions of the urban water system are fulfilled but it could even be done better. According to the definition of a problem, the desired situation has to be known in order to define a problem. For this purpose, an objective tree is constructed to analyse the objective and specify criteria. Only objectives, which are related to water management and energy, are evaluated in this scheme. To construct this tree, information from the former chapter has been used. In chapter 1 the key elements of sustainability where covered. Sustainability can be regarded in three dimensions, namely social, economic and ecological sustainability. For social sustainability it is useful to make a distinction between the needs of the present and future generation. For the economy and ecology this is less useful because the needs of ecology hardly change through time and economy hardly ever focuses at all on the very long term. Often there is a conflict between the economic short-term interests and the long-term social and ecological interests. Therefore, the social needs of the future generations are explicitly taken into account in the objective scheme. In the objective tree the general goal: sustainable urban watermanagement and water supply is split in four sub goals, these are:
Socially sustainable: needs of future generations
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 42
Socially sustainable: needs of present generations Economic sustainable Ecologically sustainable
These sub goals need to be elaborated further because the sub goals are still very general. The sub goals are made more concrete by the goals on the second level. For these second level objectives, it is possible to seek criteria. These criteria are necessary to be able to make a judgment of current and future water systems. However, for some objectives it is hard to make the criteria operational, for other objectives making the second level objectives more concrete by criteria leads to neglecting a lot of relevant factors. For this reason in this chapter the second level objectives are evaluated for the current situation, threats and opportunities. Each second level objective is a separate paragraph in this chapter.
Figure 3-2: Scheme of the objective tree for sustainable water management
Sustainable urban water system and water supply
Socially sustainable for
Self supporting system
Reliable wastewater
Energy efficiency
Variation in water level and water system
dimensions
transported
document
Water retaining capacity
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 43
3.1 Sustainable use of water What is sustainable use of water? Several approaches towards sustainability were presented in former chapters. Moreover, both the national as the European approach towards water management were outlined. Some elements can be extracted from this information. Sustainable water use means to prevent:
Depletion of groundwater or surface water; the water use may not be larger than the speed of regeneration.
Problems in surrounding areas as a result of water use in the city.
3.1.1 Present situation There are two problems that are related to water use in urban areas. The first problem is that water use causes water depletion in other areas, such as nature reserves. The second problem is the use of drinking water for low quality purposes. In particular if water scarcity or water depletion occurs at the same time this is a problem. Water use causes water depletion The extraction of groundwater, which forms a large part of the water supply, causes water depletion in nature reserves. Water extraction contributes for 93.000 ha to areas suffering from water depletion. (Vewin, 2004) To meet the objectives laid down in the Water Evaluation policy document: by 2010 a 40% reduction in the area of countryside suffering from water depletion as compared with the 1985 figure, must be realized (4th Policy document on water). Besides, water extraction, treatment and transport costs energy, money and requires chemicals. High quality water for low quality purposes The drinking water supply in the Netherlands is of a very high quality; this quality is reached by input of chemicals, energy and money. The high quality is not needed for a large part of the water purposes, since about 50% of the total water use of 126 litres/capita/day is used for toilet flushing and cloth washing. At the same time the internal source of clean water in the city, rainfall, is hardly used and transported through the sewer system to the wastewater treatment plant. The external water supply from drinking water pipes is approximately 300 mm a year (DHV, VNG, 1996), whereas the supply by rainfall is 750 mm a year in the Netherlands. Chapter 6.2 presents an analysis, to find out whether it is possible to design a city, which only needs the input of rainfall while no additional supply is needed.
3.1.2 Threats There are some threats, which prevent the implementation of a sustainable urban water supply. Theoretically, the use of local rainfall for low quality purposes could both decrease water supply to the urban area from the surrounding areas and the use of high quality water for low quality purposes. However, some problems arise here which relate to social needs, such as public health and operational safety. Experiments with ‘dual networks’, which supply two qualities of water, have not turned out to be a success. The main reason for this failure is the fact that they impose a health risk. Moreover, these networks need more material and energy input, which can be regarded as an environmental problem. Besides, enormous amounts of capital have been invested in the current system; this makes the change to a new system difficult. The threats can be summarized as follows:
The government has restricted use of ‘dual networks’ for household purposes (VROM, 2004).
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 44
The use of rainwater, which has not been treated properly, can impose a health risk if rainwater has become contaminated with pathogen organisms by contact with roofs. (Kiwa, 2003)
Large amount of capital have been invested in the current system. Rainwater collection systems for household are not financially feasible.
3.1.3 Opportunities
There are opportunities as well for more sustainable water use. Groundwater extraction shows a decreasing trend and water use has decreased during the last years. By using disconnection techniques, local rainfall is not transported to the sewer system but added to the groundwater. The following list presents the most important opportunities.
Groundwater extraction is decreasing. Water use is decreasing. Development of water saving technology. Decrease of water use could be realized by education and water saving campaigns. It could be possible to supply different qualities of water depending on the water use
purpose. Disconnection facilities increase groundwater recharge and can decrease groundwater
depletion.
3.2 Sustainable use of energy A sustainable energy supply is an energy supply based on renewable resources, without adverse effects like climate change and air pollution. Non-renewable resources may not be depleted before alternatives have been found. In this report on sustainable urban water management the energy supply is included because the water system offers a lot of opportunities for energy conservation.
3.2.1 Present situation The two main sources of energy to households are electricity and gas supply. The energy supply is still mainly focused at conventional energy sources, because the sources are mainly non- renewable. In a sustainable approach alternatives should be found before conventional sources have been depleted. Electricity comes mainly from non-renewable resources Energy use in cities still relies for a large part on non-renewable resources. In 2002 the percentage of electricity that was generated in a sustainable way in the Netherlands, was 13% (CBS, 2004). Conservation of energy and raising the percentage of renewable resources of the total energy supply, makes the energy supply more sustainable. For an average household in 2000 the electricity use was 3 085 KWh .One KWh has a caloric value of 3.6 *106 J. Use of gas results in CO2 emission In 2002 the average household 1595 m3 gas a year was used. (CBS, 2004) The caloric value of 1 m3 gas is about 33 *106 J. One can conclude that the average energy supply from gas is much larger than the energy supply from electricity. The use of gas leads to a higher CO2 concentration in the atmosphere, which is regarded to be one of the main causes of climate change. Of the total amount of gas a large part is used for heating of buildings. This is clearly indicated by the difference between households with central gas heating and households without heating by gas. The difference of gas use between these households is 1440 m3. This opens up opportunities
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 45
because the energy use for heating is a slowly varying energy flux, which can partly be realized by using groundwater.
3.2.2 Threats There are various threats to a sustainable energy supply. One of the most important threats is the fact that sustainable energy is often more expensive. Besides, low energy prices do not lead to investments in alternative energy sources. The privatisation of the energy companies has caused reluctance to invest in alternative energy sources as well. There are the following threats:
Sustainable energy is often more expensive. Current state of the system is focused on conventional energy sources. Private status of energy companies does not necessary lead to the most sustainable energy
supply because of profit maximisation, shareholder interests and investment risks.
3.2.3 Opportunities There are opportunities as well for a sustainable energy supply; energy prices are rising and consequently, alternative energy sources become more interesting from an economic point of view. A number of water related opportunities for energy conservation can be found in literature, like the use of groundwater for heating and cooling. The following list presents the main opportunities:
Energy prizes are rising. Ratification of Kyoto protocol. Technological development of sustainable energy sources. Groundwater can be used for cooling and heating of buildings. Sustainable energy sources are applied more and are getting cheaper, water related
sources are: the use of groundwater for cooling and heating of buildings (Delft Outlook, 3.2004), the use of wastewater to generate electricity (Water21, 08/04), The use of heat from the sewer system to supply energy to the city (H2O, 14.2004).
3.3 Sustainable use of space Space is, like water and energy, one of the most important resources for a city. Once space has been put to use for infrastructure or development, in practice the situation is often irreversible. What is sustainable use of space? If the use of space is flexible and combines multiple functions, the options for future generations are kept open as much as possible and space is used efficiently. Therefore, the multifunctional use of space is the criterion for sustainable use of space. In his research Entrop (2004) defines sustainable use of space as a three-step strategy combined with the compensation principle. The preference sequence for the use of space is as follows:
1. Build within urban area 2. Build in an area with a low ecological value 3. Build in an area with a high ecological value
If it is not possible to build within the city borders, the compensation principle should be used. Another area with the same surface should be developed to an ecologically valuable area. This approach leads to concentrations of activities in the urban area and therefore also to multi functional use of space.
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 46
3.3.1 Present situation Land we use for certain purposes cannot easily be used by next generations for other purposes, or in a more general way; our use of space restricts the possibilities for future generations. This leads to a complication because sustainable development is about fulfilling both the need of the present generation and the need of next generations. Increase of pressure on space In the coming decades more space is required for the growing population and there is a higher demand for houses because families are getting smaller. Besides, more space is needed for infrastructure and water storage. Consequently, there is a higher pressure on space, the next figure presents the ongoing urbanisation of the Netherlands.
Figure 3-3: Urbanisation of the Netherlands
3.3.2 Threats Which factors make sustainable use of space more difficult? At first, multi-functional use of space requires cooperation and balancing of interests. These requirements make the decision making process more complex. At second, multi-functional use of space leads to intensifying of land use, which can also have negative effects on the urban living quality. In brief:
Multi functional use of space needs a lot of cooperation and willingness to share space with other functions.
Intensifying the use of space can have negative impacts on the living qualities of the city.
3.3.3 Opportunities
Opportunities for sustainable use of space are mainly related to national policy, which is focused more on an integrative and participatory approach. As a result, multi-functional use of space has more chance to succeed. Another development is the large amounts of agricultural space which in the future could be used for other purposes. The opportunities can be summarized:
The Water test (watertoets) causes different actors such as spatial planners, urban planners and water managers to cooperate.
New water policy ‘ A different approach to water’ asks for a lot of space for water storage, the scarcity of space stimulates to use this space for other purposes as well.
Further development of floating houses offer possibilities for multi functional use of space.
Much rural space could possibly be used for other functions in the future.
2005 19701900
Transitions to more sustainable urban water management and water supply
MSc Thesis Report 47
3.4 Economic sustainability In designing new water systems the economy should be taken into account. In the first chapter the ICIS triangle was presented, which symbolizes the balance between economic, social and ecologic domains. Development of social and ecological capital should not be too much