2. Jure Margeta, Snježana Knezić and Željko Rozić
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Journal of Civil Engineering and Technology, 6(7), 2015, pp. 93-112.
http://www.iaeme.com/IJCIET/issues.asp?JTypeIJCIET&VType=6&IType=7
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1. INTRODUCTION
The world today is faced with a growing number of inhabitants, concentrated in all
major cities, mostly in the coastal marine zone [1] and [2]. Cities should strive for
urban areas that contribute to local, regional, and global sustainable development.
Naturally, this also applies to urban infrastructures and services, including Urban
Water System (UWS), Figure 1. Thus, sustaining UWS is an imperative because it is
of existential importance for urban areas. The UWS comprises: water supply
infrastructure, sanitation infrastructure, drainage infrastructure, natural water bodies,
institutional and non-institutional stakeholders, and mechanisms for financing,
operation and managing the infrastructure.
The challenge of urban development is to absorb urban growth while solving the
environmental and social equity problems arising from economic and physical
concentration. Water supply and sanitation, drainage and flooding prevention,
pollution control, are infrastructures which significantly reduce environmental health
problems and thus contribute to the sustainability of cities and sustainable
development in general. The biggest challenge for UWS operation is to keep water
and wastewater flowing at affordable rate, without threatening the urban and wider
natural environment. It means that is necessary to apply integrated urban water
management that is based on the recognition that the UWS is best designed and
managed in a holistic manner. Urban water system management is an important
segment of growth and sustainability of every city especially in developing countries.
The social-economic state of urban midst, its sustainability and productivity, depend
on the state and development stage and efficiency of the UWS. Management and
development of the UWS is a complex task which is solved within a number of
constraining frames: financial, personnel, infrastructure, legislative, environmental,
cultural, civilization, etc.
The traditional management model, mainly based on experience acquired
throughout years of work, is neither sufficient nor productive any more. The systems
are complex, especially large ones, with a whole range of elements and processes,
which could not be effectively managed nor controlled with such models. Like all
complex problems and systems, UWS is also solved by system analysis process. The
problem solving methodology includes various methods and techniques, which can be
divided into two main groups [3]: (i) optimizing techniques and methods; (ii)
simulation techniques and methods. Simulation is necessary for describing and
understanding the system and processes within, while optimization is used to improve
its aspects, such as performance, efficiency, or quality. Both methods are generally
used, through development and implementation of adequate decision support system.
A feature of these models is that they can't adequately include in process simulations
non-technical system elements, social, cultural, economic and others which affect the
UWS sustainability, such as simulation of the effect of increased water prices. Second
problem is that reliability of such models depends on huge amount of quality data and
important decisions have to be made regardless of the fact that less developed UWS
lacks of such data.
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Figure 1 Conventional coastal UWS boundaries and direction of extension [2]
There is a need for appropriate management tools which take into consideration
such situations as well as all system elements, functional connection of different parts
of the system and physical infrastructure, city areas and associated water resources, as
well as social economic aspects of the problem. In view of the aforesaid, it is obvious
that particular attention must be given to proper management and control of the UWS,
respecting the needs and plans for sustainable growth and development of cities, as
well as all constraints, primarily those related to environment. These systems and
problems are solved with the System Dynamic (SD) methodology [4]. That is
simulation methodology based on system theory. The main advantage of such
approach is in analysis of the entire system that leads to more sustainable solutions
then separate design and management of elements of the system [5].
This paper will present this approach and a modelling tool, ''Object-Oriented
Programming'' (OOP) [6], used in UWS management in a holistic manner. It
represents a new way of problem approach with a group of models based on real
world concept. Implementation of OOP in integrated UWS management will be
presented, i.e. its possibilities and characteristics [7]. The paper begins with the
description of basic characteristics of SD methodology, OOP and continues with
description of the development of an integrated model and case study for the city of
Mostar. Second part of the paper shows a segment of the results and experiences
gained during the implementation to UWS analysis.
2. SYSTEM DYNAMIC METHODOLOGY AND OBJECT-
ORIENTED PROGRAMMING
Modelling of complex systems such as UWS requires a specific approach, because
processes in which management policies are defined must count on full understanding
of the effects of the proposed solution and possible system feedback. UWS modelling
can be divided into two main groups: (1) mathematical modelling of certain technical
subsystem, such as pipeline, network, water reservoir, etc. and (2) modelling of the
system in a wider sense, representing expansion of a classical technical view of other
non-technical system elements (economic, organizational etc.). The SD methodology
Conventional Boundaries of Urban Water System
Sewerage
Stormwater
Drinking
Water supply
WATER
SOURCES
RIVER
BASIN-
OTHER USES
SEA WATER MARINE
RESOURCES –
ECOSYSTEMS
URBAN AREA
NATURAL ENVIRONMENT
4. Jure Margeta, Snježana Knezić and Željko Rozić
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is the approach that helps create management policies in a holistic manner [5]. The
SD principle is applied to all types of systems, which can be described as systems
with feedback, and enables understanding of the system, not only in the context of
technical-technological solutions, but also in the context of social, political and
economic conditions [8]. The origin of the paradigm ''system dynamics'' lies in
Forrester's work on systematic approach as an intellectual tool for modelling complex
systems and consists of the process of recognizing the objects and their connections
within the system, in order to simulate its functioning [9] [10]. The SD is
mathematical realization of the developed interactions among system variables over
time and is comprised of four sectors, system environment, UWS infrastructure,
consumer and finance. From the technical point of view, many intuitive solutions
develop in the context of the so-called negative first-order feedback loops which seek
solution within one objective and based on one state variable of the system. During
modelling of dynamic behaviour of the model, four basic structures should be
recognized: (1) system limit, (2) feedback, which is the basic structural element
within the limits, (3) system state variables that represent accumulation within the
feedback, (4) variables that represent the course and show activities within the
feedback.
Both SD methodology and OOP have been applied in UWS management. N.
Grigg [11] presents a retrospective view to SD methodology, thus showing how to
apply quantitative analysis to the urban water supply system using OOP. Junying [12]
applied OOP on urban water infrastructure management. The model comprises water
demand, perspectives for urban development. Recently, the methodology of system
dynamics has been presented for studying water and wastewater network management
with respect to the financially sustainable management of UWS [12], [13].
Object-oriented programming (OOP) is a very suitable programing for system
dynamic model development. The type of programming in which programmers define
not only the data type of a data structure, but also the types of operations (functions)
that can be applied to the data structure. In this way, the data structure becomes an
object that includes both data and functions. In, addition, programmers can create
relationships between one object and another. OOP are widely implemented in areas
of engineering and programme software and have been introduced to meet the
requirements of complex and dynamic systems. The advantages of the OOP lie in its
simplicity [8], because ''what if'' scenarios can very easily be constructed and,
therefore, insight to system behaviour can be gained. On the other hand, the principles
of ''system dynamics'' are uniformly applied to social, natural and physical systems.
In this paper OOP is applied to UWS management of the city of Mostar, in order
to make the complex system more understandable to both managers and decision
makers. The platform ''STELLA'' has been foreseen. Dynamic behaviour of the
system is generated within feedback loops, Figure 2a [7] [14] [15]. Feedback loop
consists of stock – state variable of the system and course that represents inflow of
information and matter. Equations which express system policies, and explicitly or
implicitly contain objectives, are assigned to flows through regulators. The flow
regulator equation represents a detachment from the objective and formulates action
which is the result of that detachment. Stock and flow, i.e. flow regulators, are the
main functional elements of the system structure. Levels serve as sources, but can also
serve as constraints and inseparable part of the flow. The other two basic elements are
converter and connector (Figure 2b). The converter converts input data into output
data and can represent information or material quantities. The connector connects
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stock and converters, stock and flow regulators, interconnects converters, and
transfers numerical values, i.e. information. Symbols ''cloud'' are sources or
destinations of flows, going from or to external surroundings and are controlled only
by conditions within the system.
The simple loop of feedback Complex loop with one converter
Figure 2 The loops of the model
Interrelations and connections of various previously described objects, presented
by the model are a reflection of functional dependencies within the system, and
dependences with external interaction systems and surroundings. The conceptual
system development generally consists of four phases:
• system analysis (problem identification and defining system functions);
• creation of simulating system (development of the overall architecture of the system);
• creation of system objects (development based on demand analysis); and
• implementation – programming (transfer of object groups and links into the
programme).
The results of process are three models:
• object model (describes the physical structure of the system);
• dynamic model (describes profane connections in the system); and
• functional model (describes functional connections among the variables of the system
being simulated).
The presented steps of system modelling have been applied in UWS management of
the city of Mostar.
3. URBAN WATER SYSTEM MODEL DEVELOPMENT
Unlike other methods and techniques, the described methodology starts from a unique
modelling approach of all segments (elements) of the system, so that their integration
would be on the same level of abstraction, and therefore facilitate and improve that
part in development and analysis of the system. The application of ''system dynamics''
paradigm and implementation through OOP enables implementation of planning and
control process of UWS, by unique treatment of entity as an object, regardless
whether entities represent consumers, concepts, models, or other parts of consumer
interface; and connecting all those objects (system elements) into one integral system.
6. Jure Margeta, Snježana Knezić and Željko Rozić
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In preparation of the UWS management model the start-up point should be system
component analysis, followed by analysis of all elements, starting with operative-
physical level, through management and strategic level (Figure 3). After that, the flow
of information connection system should be established, i.e. interdependence between
various systems and subsystems and defining their functional dependence through
relation connections and ratios. The connections and ratios are simple algebra
functions combined with logical and special – adjusted application functions.
EXTERNAL STRATEGIC FRAME
MANAGEMNET FRAMEWORK
Figure 3 General concept of integral urban water system management in a holistic manner
The system is modelled gradually in three subsequent steps. The simplest, but
basic model of water in the UWS is prepared first, by which the following is
simulated: state and changes of water quantity in the whole system, i.e. water supply
system from intake to users; collecting/sewerage system, wastewater treatment plant
and outflow into the recipient.
In the second step water quantity model is expanded by introducing water quality
parameters/variables including mass balance and water quality parameters
concentration calculations in the system. Finely a more complex model is then
worked out by expanding the quantity and quality model with economic and
managerial factors, or social-economic factors and policies. Thus, an integral model
for analysis of urban water operation is obtained, which contains all infrastructure
system elements (configuration), describes main changes of water quality and
quantity variables in the system, and social-economic processes. The model can be
more or less complex, depending on requirements and characteristics of the system as
well as available data. At the beginning of the problem-solving process a simpler
concept of the system and problem is modelled in order to familiarize with the
behaviour of the system and model. In the next steps, the system expands to include
other elements and processes of the system according to the needs and objectives of
the planed research. The first step is to develop a system configuration model or
physical infrastructure sector.
PHYSICAL
FRAME –
DEVELOPED
URBAN WATER
SYSTEM WITH
SURROUNDINGS
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3.1. Model 1. – Urban water system configuration and water balance
The Model I describes UWS configuration and includes the following main structural
elements of the system:
1. The system of main model levels with flow and influence rates consists of the
following elements:
(i) water resources – water intake, (ii) inhabitants and other users of the
system, (iii) recipient.
2. The system of main converter elements with connectors and defined directions of
connectors consists of:
• water intake,
• water supply system (capacity, system state, losses),
• need for water – demand for water,
• potable water purification plant,
• industry consumption,
• public consumption,
• total water consumption,
• wastewater quantity,
• other water,
• sewerage system (capacity, system state, losses),
• wastewater treatment plants.
The purpose of the model is to determine the amount of water in all main elements
of the UWS based on input and output quantities and their respective processes of
transformation (converters). The system is divided into subsystems and for each
subsystem a dynamic water balance is modelled, that is used to define the state of the
amount of water in the entire planning period in accordance with the established
trends of changes of input variables and conditions/development of the system.
Subsystems and components of their water balance are:
1. Water supply subsystem:
- Water intake – water intake balance,
- Water use – water consumption balance,
- Water losses – water loss balance,
3. Wastewater subsystem:
- Wastewater generation – balance of inflowing wastewater into the subsystem,
- Sewerage system – balance of wastewater in sewerage network
4. Surface water subsystem:
- Surface water generation– balance of inflowing rainwater,
- Drainage system − water balance in the drainage system,
- Overflow – overflow balance.
5. Wastewater treatment subsystem:
- Wastewater treatment plant– water balance in treatment plant,
- Outflow – balance of water out flowing into the recipient.
8. Jure Margeta, Snježana Knezić and Željko Rozić
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The balance is determined for the key variables that determine the balance of
individual components of the subsystem, the subsystem as a whole and the system as
a whole, for each fiscal year in the planning period, using the mass balance equation
V = Qin – Qout (1)
V – Accumulation
Qin – Input
Qout – Output
Appropriate convertors are introduced in the model, as well as capacity constraints
of individual components in the system (for example water intake):
Qreq; for Qreq ≤ Qava
Qreq = { (2)
Qava; for Qreq > Qava
Qreq – Q needed
Qava – Q available
In this way, by changing certain input values it is possible to obtain the balance
state of system components, as well as the system as a whole and the dynamic trend
of changes in the entire analyzed period. For example, changes of: the number of
inhabitants and other users, water use quantity per capita/tourist, % of connection to
the network, water losses, capacity of water sources, rehabilitation of sewerage
system etc. It is possible to analyze a full range of development scenarios and thus the
situation in the urban area, UWS, environment and the impact of management
decisions in the entire planning period. All information is given as numerical values
and graphical display (trend of changes) so that changes are easily visible to all
participants.
The main components of this model are shown in Figure 4 (black colour). The
developed model comprises more elements than presented here. An abbreviated
version is presented for the purpose of a better overview of structure model. In the
next step Model 1 is upgraded with components that describe the state of quantities of
certain parameters of water pollution.
3.2. Model 2. Water quality characteristics in the system
Upgrading enables the analysis of water quality and dynamic balance of certain
substances in the whole UWS and related environment; water supply, wastewater and
surface water subsystem and receiver. The following is modelled in the water supply
system: changes in water quality in the system, work of drinking water treatment
plant, including water disinfection. A balance of waste substances found in certain
parts of the sewerage system are determined, as well as of those that flow to the
wastewater treatment plant, in the whole planning period. Afterwards, the plant sub-
system/plant operation and balance of certain pollution parameters and discharge of
treated water into the recipient and the state in the recipient are described. All this is
performed by using the equation of mass balance and certain types of reactors
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(convertors). In a similar way it is possible determine pollution load generated by a
system of surface waters and the burden of pollution in the recipient (river) is
determined throughout the whole planning period.
In the presented example only the BOD5 parameter in wastewater system has been
presented. The main components of this model are shown in Figure 4 (blue colour).
The issue of water quality in the water supply system or rainfall sewage is treated
similarly.
Figure 4 Model of the urban water system; black colour – Model 1; blue colour – Model 2;
red colour – Model 3
All indicators of the state of wastewater quality can be expressed with the
following values:
• average quantity of organic matter in wastewater (kg/day), and
• Concentration of certain parameters – pollution indicators (mg/l or kg/m3
).
It should also be stressed that, for the purpose of simplicity and good layout of the
model, only one indicator has been included in this presentation – the water quality
indicator BOD5. Naturally, the model can analyse other indicators (total suspension
solids, COD, NH3, N – nitrates, P – phosphorus, etc.). Based on the analysis of
wastewater, state of recipient and the selected degree and mode of wastewater
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treatment, all components and their interference, as well as the state of the recipient,
can be analysed.
3.3. Model 3. Management component of the urban water system
The following upgrading of the model refers to the use of the model to obtain
information necessary for the economic and financial analysis and creation of
management policies for the system. The upgrading of the water quality and quantity
model includes non-technical control variables. This primarily refers to the economic
system, i.e. to economic factors as the main drives of development and system
sustainability. For example, the impact of water fee changes on the water balance,
concentration of waste substances in UWS, plant pollution load and impact on the
environment are analyzed. In a similar way, it is possible include other variables and
management issues (e.g. climate change). In this example only key parameters that
characterize the economic system will be used for extension. The main components of
the model are shown in Figure 4 (red colour).
The presented model can be expanded and include a number of other processes in
solving the problems of sustainability of the UWS. Once the model has been
developed, it can be used for various analyzes, by introducing new variables and
processes. Modelling start with simpler analyzes and gradually expand them to the
desired level of complexity, according to the needs, but also to the available data. In
this way, the user gradually familiarizes with the system and its behaviour. The model
is supplemented based on new information and analysis is more efficient and useful. It
is a great advantage of the presented procedure.
4. CASE STUDY
The developed system dynamics UWS model can be used by water utilities to achieve
a variety of utility short and long-term objectives as well as to establish appropriate
utility policies. As an example of possible application UWS of the city of Mostar have
been used. Mostar is the largest city in the region of Bosnia and Herzegovina, situated
on the river Neretva. The city and its water infrastructure suffered great damage in the
last war, partly due to destruction and partly due to lack of maintenance. The UWS is
underdeveloped, especially sewerage system. Throughout the last decade great efforts
are being made to improve the system and increase its efficiency. Parts of this process
are research works and some results are presented in this example.
4.1. Main input data
• Population: 80000 − 87000 (growth trend 0, 55 – 0,30 %);
• specific consumption: 250 l/inhabitant/day, depending on civilization factor which is
within the range of 1,0 – 1,7 for the period of 20 years;
• Industry water consumption: 100 l/s (with annual consumption increase of 0,5 %);
• Public water consumption: 80 l/s (with annual consumption increase of 0,5 %);
• losses in water supply system: 60 %;
• development level of water supply system: 95 %;
• wastewater quantity: 80 % of specific consumption;
• development level of sewerage system : 85 %;
• losses in sewerage system: 30 %;
• water resources: average outflow in the Neretva River basin 150 m3
/s and average
groundwater abundance of the Neretva for the Mostar area: 0,4 m3
/s;
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• total number of equivalent inhabitants (PE)
• recipient flow (the Neretva River – critical dry period − min. flow): 50 m3
/s;
• discharged wastewater: obtained as output parameter of the water quantity model in
the system;
• concentration of BOD5 of recipient on upstream section: 2,0 mg/l;
• unit load of BOD5: 60 gr/PE/day (actual state and increased up to 65 gr/PE/day for
the planned period);
• wastewater mixing/dispersion coefficient in recipient: Y (from 0 to 1,0), depending
on hydraulic parameter and distance of measuring section from discharge point;
• load of recipient : 9 600 kg/day – measured on upstream section;
• permitted concentration for river water category II of the Neretva: 4,0 mg/l;
• planning period is 15 years, and time step is 1 year.
The analysis has been made in order to answer three basic policy questions:
• What would be the result/state of UWS in the next 15 if the current way of managing
continued;
• In what way and how much do certain factors affect the behaviour, state and
sustainability of the system as a whole in that period;
• Which are the main factors, i.e. factor ranking in relation to positive effect on system
sustainability.
Currently the biggest problems related to the functioning of the system are related to:
1. large water losses in the water supply system, (ii) low level of payment of services,
(iii) an increase in water use per-capita, (iv) direct and indirect pollution of the river
due to low level of population connected to the sewerage system, permeability of the
sewerage system and insufficient treatment of waste water and overflow waters from
combined sewerage system.
4.2. Analyses of the impact of population and water consumption rate
change on the UWS characteristics
The OOP utilization of analyses can be simple and complex. Simple analyses include
the estimate of the system behaviour in the planned period, such as water demand in
the coming planned period (Figure 5), wastewater quantity analysis (Figure 5), water
losses and estimate of effects which specific consumption has on water requirements
(Figure 6), if retaining the current level of system development, technological features
(water losses, infiltration in sewers, etc..), the price of services and collection of fees
for services.
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Effects on population increase on water
consumption (l/s)
Effects on population increase on wastewater
quantity (l/s) for the planned period
Figure 5 Effects on population increase on water consumption and wastewater quantity (l/s)
for the planned period
Effects of per capita water use in the
planned period on water consumption (l/s)
Effects of per capita water use in the planned
period on wastewater quantity (l/s)
Figure 6 Effects of per capita water use in the planned period on water consumption and
wastewater quantity (l/s)
These results clearly show the changing water balance in UWS in the future
period with a planned increase of the city and its population and the existing level of
technological development of the system.
More complex analyses are estimates of effects of the system on water quality and
wastewater quantity flowing to the treatment plant and the recipient, Figure 7.
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a)Effects of population increase on generation of
BOD5 in wastewater system and at the plant
(kg/day)
b)Effects of population increase on load of BOD5
(kg/day) discharge in recipient, case without
wastewater treatment
Figure 7 Effects of population increase on generation of BOD5 in wastewater system and
recipient
The model provides direct analysis of population effect on BOD5 concentration in
the recipient (mg/l). Figure 8 shows two cases: (i) wastewater is not treated and (ii)
wastewater is treated at treatment degree of 90%, (wastewater mixing coefficient in
recipient is Y=0,6).
Figure 8 graphic presentations of population increase effects on BOD5 concentration in the
recipient for the case when wastewater is not treated (1) and when it is fully treated (2)
A simple and realistic graphic presentation of results and trends of change of the
system state facilitates in the planning period, contributes to a better understanding of
the problem and making sustainable decisions. Namely, data and number of
information increase significantly, enabling full perception of the problem.
The result of the analysis is the fact that the UWS is unsustainable. All trends of
parameter changes in the planning period are negative in relation to the desired
sustainability of the system and the environment. The system must be improved in
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order to be functional and sustainable. Someone might say that it could be known
without analysis. True, it is obvious to experts but the difference is that
implementation of the displayed enables us to follow the trend of changes and the
situation in the future, as well as interdependence/impact of individual parameters.
Trends of changes and the situation are easy to understand for decision makers. By
application of the presented model it is possible to quickly implement a whole range
of analyzes of various scenarios and management decisions, with the aim of
minimizing the use of resource inputs into the system, maximizing the desired effects
and reducing adverse impacts. For example, the analysis of the effects of reduction of
water losses from the water supply network and sewerage system, increase of % of
connections to the system, on the water balance, wastewater and economic state of the
company and pollution of the river.
4.3. Analyse of water fees change impact on UWS characteristics
Analyses of effects the economic and financial factors such as water fees have on the
state and behaviour of the system are of particular importance. These analyses are
important, because they give a full image of the user-owner relation. These several
examples of possible analyses are presented. The economic system structure is
composed of the following components: water price (Figure 9), water tariff collection,
municipality income, municipality income per capita, system operating and
maintenance costs, general standard, etc.
Figure 9 Perspectives of water price growth for the planned period; KM/m3
(KM-BiH
currency)
The main driving factor of the existing economic system is water price. The
creation of normal market and economic relations in the UWS requires formation of a
certain water services price, which includes full costs of the system. The change in
water price creates new circumstances in view of establishing the new organizational
and institutional management unit, as well as in water demand processes, i.e. water
consumption. Increase of water price up to a certain limit (depending on social
conditions) creates the sufficient and required condition for sustainable development
of the UWS. Following is the information regarding water fee changes, relevant for
decision makers:
• reduction of losses in water supply network;
• reduction of specific water consumption, or total water intake;
• increase of municipal income (if the municipality is the owner);
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• total wastewater quantity;
• BOD5 load of wastewater system;
• BOD5 concentration in river; etc.
The main presumptions, built in the model are:
• more money or higher revenue, better maintenance and operation of the system and
therefore less water losses and less leakage of wastewater;
• more money, better connection of inhabitants to water supply and sewerage system;
• Higher price, higher saving and reduction of per capita water consumption.
Relations describing these interdependences are defined in the model based on
experience and data from literature. Each particular case requires specific research
and definition of functional connections among these factors. The example of the
effect of water price change on overall water consumption is presented in Figure 10.
The difference in total consumption is observable, i.e. the effect of economic factor,
''water price'', as the key economic parameter. Economic factors affected the reduction
of:
• per capita water consumption and
• water losses in water supply network.
Figure 10 Water consumption (l/s) in settlements: 1. price increase of 1–4 KM/m3
; 2. water
price unchanged, 1 KM/m3
Based on that parameter solely (water price) a detailed analysis can be conducted
for determining the overall tariff system, where optimal water price would be defined
for such system, i.e. cost-effectiveness, efficiency, productivity, etc. would be
determined. Similar analysis could be conducted for other parameters and their
sensitivity and effect on the overall system could be seen, Figure 11.
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Figure 11 Wastewater quantities in planned period (l/s): 1. price increase of 1–4 KM/m3
;
2. water price unchanged 1 KM/m3
Figure 12 presents the analysis how economic factors affect the quantity and
intensity of wastewater flowing to the treatment plant and recipient, i.e. the conditions
of wastewater discharge.
a) Concentration of BOD5 (mg/l) in wastewater
flowing to the treatment plant: (1) water price
increase; (2) price unchanged
b) Quantity of BOD5 (kg/day) in wastewater
flowing to the treatment plant: (1) water price
increase; (2) price unchanged
Figure 12 Change of quantity and concentration level of BOD5 at wastewater treatment plant
influenced by economic factors.
In the context of the previous analysis, the effect of economic factors, i.e. ''water
price'', on load and concentration of BOD5 of the recipient, can be perceived; Figure
13. The initial state of BOD5 concentration in the recipient is 4,0 mg/l for both
models. At the end of the planned period the BOD5 concentration increase is higher in
the first case (4,8 mg/l), than in the second (4,35 mg/l), as the result of change in
quantity and concentration of wastewater.
17. System Dynamic Methodology Application in Urban Water System Management
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Figure 13 Change in concentration of BOD5 (mg/l) in recipient, with treatment degree of 0 %
and Y = 0.6 for the cases of: (1) price increase; (2) unchanged price
The model enables simulation and changes of municipality income from service
charge; Figure 14. The income increases in both cases, and at the end of the planned
period it is 1.3 × 106
KM/month, which is also a significant increase in municipal
budget. This creates more favourable conditions and bigger possibility for
rehabilitation of urban infrastructure (water supply and sewerage), as well as for
construction of new infrastructure.
Figure 14 Increase of municipality income (KM/month) from water services charge in two
cases: (1) water price increases from 1,0 KM/m3
to 4,0 KM/m3
(model MM-UWS); (2) water
price is constant and is 1,0 KM/m3
for the entire planned period
Based on the analysis of effects of various components on the system itself and
the surroundings, the following conclusions can be drawn:
Income from water services charge, with defining the water price and its increase
until the end of the planned period, which results in increase of municipality budget,
18. Jure Margeta, Snježana Knezić and Željko Rozić
http://www.iaeme.com/IJCIET/index.asp 110 editor@iaeme.com
and on the other hand, reduces water consumption. It is the only possible and
sustainable approach to water use;
By introducing the economic category in the UWS management model, all other
relations are created within the system, as well as in economic relations, i.e. in the
society as a whole;
Municipal income (or income of the company managing UWS) increases
considerably, enables a number of activities regarding organization and functioning,
and provides rehabilitation measures for the existing infrastructure and measures
regarding construction and improvement of the new water supply and sewerage
network;
All changes of parameter values within the system are the result of ''water fee''
increase; therefore, it is the main managerial element for sustainability of the system.
The aforesaid does not present all analyses which have been conducted by
application of the developed system dynamics model. Presented methodology enables
analysis of both system behaviour and its influence to natural and socioeconomic
environment in a situation with a limited budget, as it is usual in developing countries
like Bosnia and Herzegovina. Such approach fully supports making feasible decisions
in given circumstances. Other numerous analyses are also possible, which improve
significantly the level of information of decision makers and managers, considerably
improving the management reliability and sustainability.
6. CONCLUSION
Based on the aforesaid, it can be concluded that the system dynamic methodology is
suitable, acceptable and desirable for the management of the UWS equally in
developed as well as less developed urban areas and therefore should be used more.
Design and management of the UWS based on an analysis of the entire urban water
system as it is presented will lead to more sustainable solutions then separate design
and management of the system elements. This particularly applies to cases when the
local owner is indebted and when there is a need for a more complete analysis of the
effects of indebtedness and investment on the sustainability of the communal water
system. Similar refers to the analysis of the impact of climate change on UWS and
similar problems where equal importance is given to economic, ecological and social
features of the problem and input data are global and imprecise [16]. The biggest
advantage of this procedure is that useful information for management can be
obtained based on a restricted data fund as it is case in less develop areas as it is
Mostar in Bosnia and Herzegovina.
The actions identified as needed as the result of the study include:
• Reduction of water losses from water supply systems to the acceptable level of 15–
20% soon as possible
• Introduction of economic prices of water uses
• Providing of alternative water sources for the water supply systems supplied only
from one source
• Proclamation of sanitary protection zones for water intake
• Controls on pollution from solid waste by implementation EU directives
• Modify existing predominately combined sewerage system into separate system
• Control of surface water flow within urban areas by development of appropriate
storm water drainage system.
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The OOP is flexible programming tool, very easily adaptable to the dynamic
system methodology, using a whole range of interconnected and interdependent
parameters and elements. One of the principal advantages of OOP techniques over
procedural programming techniques is that they enable programmers to create
modules that do not need to be changed when a new type of object is added. A
programmer can simply create a new object that inherits many of its features from
existing objects. Therefore, it can be concluded that implementation of the OOP has
the following advantages:
• simple approach in preparing a full and comprehensive (integral) management model,
• faster and simpler formulating of new alternatives or management scenarios then
traditional simulation and optimization techniques,
• easy and simple system transformation and adjustment to other conditions and states
of the system,
• possibility of planning and forecasting the state of the water system for a certain
period of time.
Modelling is simple and has the features of "learning by working" so that at the
beginning of the problem solving process it is not necessary to have all the
information, but only basic. During the development of the model and by gradual
problem analysis, the model and system are upgraded on the already achieved results
so that the process is rational and reliable. All stakeholders can be involved in the
implementation of the model and ongoing analysis of the problem during the whole
period of operation. Because of the graphical representation of the system and
dynamic characteristics of the process being analyzed, as well as the visibility of the
cause and effect connection in the system, everything is easily recognizable even to
non-professionals. Stakeholders can quickly and accurately see a result of a certain
policy proposal for the state of the system as a whole and related environment.
Therefore, stakeholders can easily participate in the whole process of analysis and
problem-solving which is very important for decision makers and is a main perquisite
for sustainable development. The platform STELLA is simple and easy to apply.
The biggest criticism that engineers usually have relates to the fact that the model
is not based on complex hydraulic or similar technological models used for operation
simulation of the UWS. They described object systems as overly simplistic models of
the real world. However, the purpose of the presented modelling is not an analysis of
hydraulic state of the system, but getting information necessary to create system
management policies, for which comprehensive technical system modelling is not
always necessary, although it is always advisable if there are good input data. The
developed models enable enhancing the sustainability of the system in situations
where all the technical details of the system and related environment are not well
known. We hope that the presented will be useful for engineers and researchers.
REFERENCES
[1] Leslie Roberts, 9 Billion?. Science, Vol. 333(6042), 29. July 2011, pp. 540–543.
[2] UNEP/PAP, Integrated Coastal Urban Water System Planning in Coastal Areas
of the Mediterranean, Priority Actions Programme, 2007.
[3] Margeta, J. Book Water resources management. Faculty of Civil Engineering,
University of Split, Croatia 1992, (in Croatian).
20. Jure Margeta, Snježana Knezić and Željko Rozić
http://www.iaeme.com/IJCIET/index.asp 112 editor@iaeme.com
[4] Elshorbagy, A. and Ormsbee, L. Object-oriented modelling approach to surface
water quality management. Environmental Modelling and Software, 21(5), 2006,
pp. 689–698.
[5] Stave, K. A. A system dynamics model to facilitate public understanding of water
management options in Las Vegas, Nevada. Journal of Environmental
Management, 67, 2003, pp. 303–313.
[6] Simonovic, S. Tools for Water Management One View of the Future. Water
International, 25(1), 2000, pp. 76–88.
[7] Rozić, Ž. Optimization of the performance of urban water system, Ph.D.
Dissertation, University of Mostar, Bosnia and Herzegovina, 2009. (in Croatian).
[8] Odanaka, T. Environment system and dynamic management decision. Applied
Mathematics and Computation, 120, 2001, pp. 255–263.
[9] Forrester, J. W. Urban Dynamics. Cambridge: MIT Press, 1971.
[10] Forrester, J. W. Industrial Dynamics. Cambridge: MIT Press, 1961.
[11] Grigg, N. S. Systemic Analysis of Urban Water Supply and Growth
Management. Journal of Urban Planning and Development, 123(2), 1996, pp.
23–33.
[12] Rehan, R., Knight, M. A., Haas, C. T. and Unger, A. J. A. Application of system
dynamics for development financially self-sustaining management practices for
water and wastewater systems. Water Research, 45(16), 2011, pp. 4737–4750.
[13] Rehan, R., Knight, M.A., Haas, C. T. and Unger, A. J. A. Development of a
system dynamics for financially sustainable management of watermain networks.
Water Research, 47(20), 2013, pp. 7184–7205.
[14] Surendra, H. J. and Deka, P. C. Effects of Statistical Properties of Dataset in
Predicting Performance of Various Artificial Intelligence Techniques for Urban
Water Consumption Time Series. International Journal of Civil Engineering &
Technology, 3(2), 2012, pp. 60–69
[15] Costanza, R., Duplisea, D. and U. Kautsky. Ecological Modelling on modelling
ecological and economic systems with STELLA. Ecological Modelling, 110,
1998, pp. 1–4.
[16] Costanza, R. and Voinov, A. Modelling ecological and economic systems with
STELLA: Part III. Ecological Modelling, 143(1–2), 2001, pp. 1–7.
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Journal of Civil Engineering and Technology, 6(7), 2015, pp. 93-112.
http://www.iaeme.com/IJCIET/issues.asp?JTypeIJCIET&VType=6&IType=7
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1. INTRODUCTION
The world today is faced with a growing number of inhabitants, concentrated in all
major cities, mostly in the coastal marine zone [1] and [2]. Cities should strive for
urban areas that contribute to local, regional, and global sustainable development.
Naturally, this also applies to urban infrastructures and services, including Urban
Water System (UWS), Figure 1. Thus, sustaining UWS is an imperative because it is
of existential importance for urban areas. The UWS comprises: water supply
infrastructure, sanitation infrastructure, drainage infrastructure, natural water bodies,
institutional and non-institutional stakeholders, and mechanisms for financing,
operation and managing the infrastructure.
The challenge of urban development is to absorb urban growth while solving the
environmental and social equity problems arising from economic and physical
concentration. Water supply and sanitation, drainage and flooding prevention,
pollution control, are infrastructures which significantly reduce environmental health
problems and thus contribute to the sustainability of cities and sustainable
development in general. The biggest challenge for UWS operation is to keep water
and wastewater flowing at affordable rate, without threatening the urban and wider
natural environment. It means that is necessary to apply integrated urban water
management that is based on the recognition that the UWS is best designed and
managed in a holistic manner. Urban water system management is an important
segment of growth and sustainability of every city especially in developing countries.
The social-economic state of urban midst, its sustainability and productivity, depend
on the state and development stage and efficiency of the UWS. Management and
development of the UWS is a complex task which is solved within a number of
constraining frames: financial, personnel, infrastructure, legislative, environmental,
cultural, civilization, etc.
The traditional management model, mainly based on experience acquired
throughout years of work, is neither sufficient nor productive any more. The systems
are complex, especially large ones, with a whole range of elements and processes,
which could not be effectively managed nor controlled with such models. Like all
complex problems and systems, UWS is also solved by system analysis process. The
problem solving methodology includes various methods and techniques, which can be
divided into two main groups [3]: (i) optimizing techniques and methods; (ii)
simulation techniques and methods. Simulation is necessary for describing and
understanding the system and processes within, while optimization is used to improve
its aspects, such as performance, efficiency, or quality. Both methods are generally
used, through development and implementation of adequate decision support system.
A feature of these models is that they can't adequately include in process simulations
non-technical system elements, social, cultural, economic and others which affect the
UWS sustainability, such as simulation of the effect of increased water prices. Second
problem is that reliability of such models depends on huge amount of quality data and
important decisions have to be made regardless of the fact that less developed UWS
lacks of such data.](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)