urban water infrastructure- finding simplicity in complexity

Urban water management addresses all water-related issues in cities, and its functioning is crucial for human well-being. The water infrastructure is usually in place in form of pipe networks, supplying water in the city and draining rain and wastewater out of it. Alike the city itself, the water infrastructure in cities grew over decades resulting in organic and complex systems. In nature and many other engineered systems, networks can be described based on graph theory. With that theory simple coherences in such systems can be identified, bringing order and simplicity in these complex structures. The focus of this research is a better understanding of principles and characteristics of grown infrastructures based on graph theory. As they are crucial for managing and preserving the high level of service in industrialized countries and enable it in developing countries. If enough data of water networks is available, hydraulic network models are powerful instruments to assess and plan these systems. One key pillar of this research will be the determination of the amount of network information being necessary for different assessment and simulation techniques and for reconstructing missing information. This innovative concept of evaluating the assessment techniques will be developed and established in this project. Because structures in urban water management have life expectancies of up to 100 years or more, urban water systems as implemented today are strongly influenced by historical decisions and implementations. In the same way, current decisions will have a long-term impact on these systems. Therefore, it is also important to understand what happened in the past and how these implementations influence todays systems. However, information on historical systems is very rare. During the growth process of the network some information on the system could have been lost. Furthermore, due to its location underground the information is hard to collect. Moreover, the developed concept is explored in terms of reconstruction of such information on historical systems. The hypothesis is that historical networks can be reconstructed with different available data sources (orthophotos, etc.). If the concept is successfully proven additional benefits for cost efficiency, rehabilitation planning, future planning as well as for managing and preserving the level of service can be gained. In addition, the identification of drivers for robust, resilient and flexible future planning of infrastructure is a key question of this proposal and will be assessed within this project.

Many people start their day in the morning by going to the bathroom. Water comes out of the tap as a matter of course and wastewater is carried away. But the high degree of reliability that underlies water infrastructure is quickly forgotten. This infrastructure often lies hidden beneath the city with little public awareness. Yet these systems, which are part of the critical infrastructure, require increased attention so that the high quality of this service can be guaranteed even in the event of unexpected incidents and future developments. Social networks have also become an integral part of everyday lives. Some individuals act as hubs with many followers and friends or with a high reach. There are thus different types of connections between the individuals, which ultimately form a social network. In such a network, everyone knows more or less everyone with a few degrees. This is called the small world phenomenon. This phenomenon also applies to water infrastructure, which can also be described by a network of nodes and connections (a so-called network graph). For example, water packages should be transported as directly as possible from the source to the consumer in order to maintain water quality. However, during construction work or disruptions in the water infrastructure, various connections may be temporarily out of service. To ensure that networks still function under these conditions, they are often equipped with double and multiple flow paths. The calculation of these multiple flow paths can no longer be simple and trivial, and water networks are therefore complex networks. For planning and maintenance of these water networks, hydraulic simulations can be of benefit. However, these often require extensive data and calculation efforts. However, many scientific and practical questions could already be addressed with mathematical description of the water network and answered without complex hydraulic simulations. In the basic research project 'ur simple', simplicity is sought in the complexity of water networks that have grown over decades, and possible applications but also limitations of graph-based approaches are identified. As an example, in the design of water infrastructure, the least expensive design has the least resistance to disruption. Here, a trade-off between cost and reliability must be found. Thus, a new approach based on graph theory has been developed, which considers the most optimal design while also considering resilience. The problem of residence time in water network was also re-evaluated using graph-based approaches, enabling a completely new and more efficient approach. In summary, the project ur simple has taken a decisive step towards a better understanding of the complexity of water networks and has identified influencing factors for sustainable, resilient and flexible strategies in order to maintain the high standard of water infrastructure in the future.