Chapter 3 Decision Support Model (IUWS-DSM) - Tubdok

Composition of Modern Urban Water System
indirect potable reuse
subsystem 2 transmission subsystem 3 distribution
Water Source
Desired Water
Legend:
direct non-potable reuse
subsystem 1
Water
Usage collection
direct utilisation (roof-water)
indirect utilisation (surface runoff)
conventional water flows possible water pathways
Chapter 2 · New Conception 11
subsystem 4
Used Water
Figure 5: Composition of modern urban water system
2.1.3 Hierarchy of urban water system
back to
nature
collection
subsystem 5
Rainwater
In the last decades, there are extensive discussions about the forms of urban water
systems. Typical argumentation is among centralised, de-centralised and semi-centralised
water systems. Modern cities are the extremely complex aggregates, which usually cover big
area with condensed large population, associated with multi-functions. Meantime, the water
shortage caused by either the water sources or the capacity of water infrastructure is another
ineluctable issue in cities. Therefore, the different design method is conceived.
The new conception structures the urban water system in the hierarchy. Based on the
features and emphasises, the entire urban water system is divided into four levels consisting
of two types of water entities, i.e. the ZONE type and the GROUP type (Figure 6). The water
entity of ZONE type is planned and designed in the holistic perspective base on the area. It
acts more as a container comprising other smaller but more detailed water entities. It stays in
the upper levels of the hierarchy. The water entity of GROUP type holds the grouped water
end-users that form the functional units of cities, such as hospitals, schools and shopping
centres, as well as multifunctional skyscrapers, etc., whereby the grouped water end-users
have specified and detailed water usage (more details in § 2.2.1.1). Regardless of the types,
each water entity can be planned and managed as an independent unit in the hierarchy. The
water entities in four levels are defined and explained as follows.
City Area (CA). It represents the whole urban water system or one absolute independent
water system in urban area, which is going to be the final IUWS. It may not be equal to the
total city area by its political meaning. This means it follows the natural status. In this level, its
main tasks are to set up the whole water system, implement master planning, and generate
directive information and strategic overview. Due to the large scale of CA, the plan of water
systems is in a rough way, where many details and factors are skipt. In order to achieve a
finer design, the second level in the hierarchy is constructed.
Urban District (UD). The city area is divided into certain small sections, whereby each
section has its independent water entity that is defined as Urban District. It can coincide with