This research project includes the maintenance, upgrading and extension of the Decision Support System that developed by NTUA for EYDAP in the framework of the research project “Updating of the supervision and management of the water resources’ system for the water supply of the Athens’ metropolitan area”. The project is consisted of the following parts: (a) Upgrading of the Data Base, (b)Upgrading and extension of hydrometeorological network, (c) upgrading of the hydrometeorological data process software, (d) upgrading and extension of the Hydronomeas software, (e) hydrological data analysis and (f) support to the preparation of the annual master plans

The Ministry of Environment, Physical Planning & Public Works assigned to a consortium of consultancy companies the Project "Development of a new software platform for the management and operation of the National Databank for Hydrologic and Meteorological Information - 3rd Phase within a GIS environment and relevant dissemination actions". In the framework of the specific project a research team of NTUA undertakes a part as subcontractor. NTUA delivers methodologies for further development of the databases and applications of the Databank and their migration into a web platform (including the experimental node openmeteo.org for free data storage for the public). Specifically, using the knowhow that has been developed in the past by Research Teams from the Department of Water Resources of the School of Civil Engineering a database system and software applications (included hydrological models) are created fully adapted for operation over the Internet. NTUA's contribution is primarily on the design of the new system and the hydrological and geographical database the development of distibuted hydological models, the adaptation of the system to the WFD 2000/60/EC and on supporting dissemination activities. Finally NTUA will participate in the technical support and pilot operation of the project after its delivery from the consortium to the Ministry.

More information is available at http://www.hydroscope.gr/.

The project's rationale lies in the Water Framework Directive,which demands an integrated approach to water management. This requires an ability to predict how catchment processes will interact. In most contexts, it is not feasible to build a single predictive model that adequately represents all the processes; therefore, a means of linking models of individual processes is required.The FP5 HarmonIT project's innovative and acclaimed solution, the Open Modelling Interface and Environment (OpenMI) met this need by simplifying the linking of hydrology related models.Its establishment will support and assist the strategic planning and integrated catchment management.

The project aims at providing support to decision-making processes within the direction of integrated management of water resource systems at a variety of scales. Several methodologies and computing tools are developed, which are incorporated into an integrated information system. The main deliverable is an operational software package of general use, which is evaluated and tested on two pilot case studies, concerning hydrosystems in Greece with varying characteristics (Karditsa, Dodecanesus). The end-product of the project is a software system for simulation and optimisation of hydrosystem operation, as well as a series of separate software applications for solving specific problems, aiming at producing input data to the central system or post-processing of the results. The project includes eleven work packages, eight for basic research, two for industrial research and one for the pilot applications.

Due to the dry climate of the surrounding region, Athens has suffered from frequent water shortages during its long history but now has acquired a reliable system for water supply. This extensive and complex water resource system extends over an area of around 4000 km2 and includes surface water and groundwater resources. It incorporates four reservoirs, 350 km of main aqueducts, 15 pumping stations and more than 100 boreholes. The water resource system also supplies secondary uses such as irrigation and water supply of nearby towns. The Athens Water Supply and Sewerage Company (EYDAP) that runs the system commissioned this project, which comprises: (a) development of a geographical information system for the representation and supervision of the external water supply system; (b) development of a measurement system for the water resources of Athens; (c) development of a system for the estimation and prediction of the water resource system of Athens utilising stochastic models; (d) development of a decision support system for the integrated management of water resource system of Athens using simulation-optimisation methodologies; and (e) cooperation and transfer of knowledge between NTUA and EYDAP.

The main objectives of the research project are the evaluation and management of the water resources, both surface and subsurface, of the Sterea Hellas region, and the systematic study of all parameters related to the rational development and management of the water resources of this region. Another objective of the project, considered as an infrastructure work, is the development of software for the hydrological, hydrogeological and operational simulation of the combined catchments of the study area. The development of the software and, at the same time, the development of methodologies suitable for the Greek conditions will assist in decision-making concerning the water resources management of Sterea Hellas and of other Greek regions. The project also aims at the improving of the cooperation between the National Technical University of Athens and the Ministry of Environment, Planning and Public Works. This is considered as a necessary condition for the continuous updating of the project results as well as for the rational analysis of the water resource problems of the Sterea Hellas region. The specific themes of Phase 3 are: (a) the completion of the information systems of the previous phases, which concerned hydrological and hydrogeological information, by including two additional levels of information related to the water uses and the water resources development works; (b) the development of methodologies for optimising the hydrosystems operation and the construction of integrated simulation and optimisation models for the two major hydrosystems of the study area (Western and Eastern Sterea Hellas); and (c) the integration of all computer systems (databases, geographical information systems, application models) into a unified system with collaborating components.

Since 1990 extensive funds have been spent on research in climate change. Although Earth Sciences, including climatology and hydrology, have benefited significantly, progress has proved incommensurate with the effort and funds, perhaps because these disciplines were perceived as “tools” subservient to the needs of the climate change enterprise rather than autonomous sciences. At the same time, research was misleadingly focused more on the “symptom”, i.e. the emission of greenhouse gases, than on the “illness”, i.e. the unsustainability of fossil fuel-based energy production. Unless energy saving and use of renewable resources become the norm, there is a real risk of severe socioeconomic crisis in the not-too-distant future. A framework for drastic paradigm change is needed, in which water plays a central role, due to its unique link to all forms of renewable energy, from production (hydro and wave power) to storage (for time-varying wind and solar sources), to biofuel production (irrigation). The extended role of water should be considered in parallel to its other uses, domestic, agricultural and industrial. Hydrology, the science of water on Earth, must move towards this new paradigm by radically rethinking its fundamentals, which are unjustifiably trapped in the 19th-century myths of deterministic theories and the zeal to eliminate uncertainty. Guidance is offered by modern statistical and quantum physics, which reveal the intrinsic character of uncertainty/entropy in nature, thus advancing towards a new understanding and modelling of physical processes, which is central to the effective use of renewable energy and water resources.

The main components of a decision support system (DSS) developed to support the management of the water resource system of Athens are presented. The DSS includes information systems that perform data acquisition, management and visualisation, and models that perform simulation and optimisation of the hydrosystem. The models, which are the focus of the present work, are organised into two main modules. The first one is a stochastic hydrological simulator, which, based on the analysis of historical hydrological data, generates simulations and forecasts of the hydrosystem inputs. The second one allows the detailed study of the hydrosystem under alternative management policies implementing the parameterisation-simulation-optimisation methodology. The mathematical framework of this new methodology performs the allocation of the water resources to the different system components, keeping the number of control variables small and thus reducing the computational effort, even for a complex hydrosystem like the one under study. Multiple, competitive targets and constraints with different priorities can be set, which are concerned among others, with the system reliability and risk, the overall average operational cost and the overall guaranteed yield of the system. The DSS is in the final stage of its development and its results, some of which are summarised in the paper, have been utilised to support the new masterplan of the hydrosystem management.

A decision support tool is developed for the management of water resources, focusing on multipurpose reservoir systems. This software tool has been designed in such a way that it can be suitable to hydrosystems with multiple water uses and operating goals, calculating complex multi-reservoir systems as a whole. The mathematical framework is based on the parameterization-simulation-optimization scheme. The main idea consists of a parametric formulation of the operating rules for reservoirs and other projects (i.e. hydropower plants). This methodology enables the radical decrease of the number of decision variables, making feasible the location of the optimal management policy, which maximizes the system yield and the overall operational benefit and minimizes the risk for the management decisions. The program was developed using advanced software engineering techniques. It is adaptable in a wide range of water resources systems and its purpose is to support water and power supply companies and related authorities. It was already applied to two of the most complicated hydrosystems of Greece, the first time as a planning tool and the second time as a management tool.

The development process of scenarios used within a decision support system for water resources management is discussed, based on the case of the Athens water resource system. In particular, the schematisation process of the real world hydrosystem into a model representation is analysed, as well as further information consisting a scenario, including hydrological and water demand conditions, operational constraints, targets and their priorities, management objectives, and methodological assumptions used in decision making, is discussed

A decision support tool is developed for the management of water resources, focusing on multipurpose reservoir systems. This software tool has been designed in such a way that it can be suitable to hydrosystems with multiple and very often contradictory water uses and operating goals, calculating complex multi-reservoir systems as a whole. The mathematical framework is based on the original scheme parameterization-simulation-optimization. The main idea consists of a parametric formulation of the operating rules for reservoirs and other projects (i.e. hydropower plants). This methodology enables the decrease of the decision variables, making feasible the location of the optimal management policy, which maximizes the system yield and the overall operational benefit and minimizes the risk for the management decisions. The program was developed using advanced software engineering techniques. As proved two detailed case studies, it is flexible enough and thus suitable for use to a wide range of applications, so it can be helpful to water and power supply companies and related authorities.

Optimisation of a multiple-reservoir system becomes increasingly complex when conflicting water uses exist, such as water supply, irrigation, hydroelectric power generation etc. Hydronomeas is a software tool, suitable for simulating and conducting a search for the optimum water resources management policy of a multi-purpose hydrosystem. The mathematical model is based on recent introduction and theoretical development of parametric rules for operation of multiple-reservoir systems. Software implementation was such performed that the model can be easily applied to a wide range of hydrosystems and that representation will be as realistic as possible, incorporating all natural, operational, environmental and other restrictions. Hydronomeas consists of several subsystems, including operational simulation, optimisation and visualisation. The first two cope with goals concerning both consumptive and energy-oriented water uses. Hydronomeas has been applied on the hydrosystem comprising all existing and under construction projects of the Acheloos river, its planned diversion and the related projects in Thessalia.

An alternative method to both the design storm approach and the continuous simulation of historic or synthetic storms is presented. The method is based on, and uses as the only input, the intensity-duration-frequency (IDF) curves of the particular urban catchment of interest. The main concept is to keep the design storm approach for the determination of the total characteristics of the design storm event, i.e. duration and depth extracted from the IDF curves of the particular region, and use a disaggregation technique to generate a ensemble of alternative hyetographs (instead of adopting a unique arbitrary design time profile). The stochastically generated hyetographs are then entered into a rainfall - runoff model and then routed through the sewer network in order to simulate the hydraulic performance of the sewer network. This enables the determination of the conditional distribution of the outflow peak, which can then be utilised for studying the design characteristics and the behaviour of the sewer network.

The water supply of Athens, Greece, is implemented through a complex water resource system, extending over an area of around 4 000 km2 and including surface water and groundwater resources. It incorporates four reservoirs, 350 km of main aqueducts, 15 pumping stations, more than 100 boreholes and 5 small hydropower plants. The system is run by the Athens Water Supply and Sewerage Company (EYDAP). Over more than 10 years we have developed, information technology tools such as GIS, database and decision support systems, to assist the management of the system. Among the software components, “Enhydris”, a web application for the visualization and management of geographical and hydrometeorological data, and “Hydrognomon”, a data analysis and processing tool, are now free software. Enhydris is entirely based on free software technologies such as Python, Django, PostgreSQL, and JQuery. We also created http://openmeteo.org/, a web site hosting our free software products as well as a free database system devoted to the dissemination of free data. In particular, “Enhydris” is used for the management of the hydrometeorological stations and the major hydraulic structures (aqueducts, reservoirs, boreholes, etc.), as well as for the retrieval of time series, online graphs etc. For the specific needs of EYDAP, additional GIS functionality was introduced for the display and monitoring of the water supply network. This functionality is also implemented as free software and can be reused in similar projects. Except for “Hydrognomon” and “Enhydris”, we have developed a number of advanced modeling applications, which are also generic-purpose tools that have been used for a long time to provide decision support for the water resource system of Athens. These are “Hydronomeas”, which optimizes the operation of complex water resource systems, based on a stochastic simulation framework, “Castalia”, which implements the generation of synthetic time series, and “Hydrogeios”, which employs conjunctive hydrological and hydrogeological simulation, with emphasis to human-modified river basins. These tools are currently available as executable files that are free for download though the ITIA web site (http://itia.ntua.gr/). Currently, we are working towards releasing their source code as well, through making them free software, after some licensing issues are resolved.

A presentation of two free software application for environmental management, developed in National Technical University of Athens. Enhydris is an Information system - server software for the management, storage and retrieval of hydrometeorological data, accessible through the internet. Enhydris is used by the National Data Bank of Hydrometeorolical Information (Hydroscope) and it also used by other agencies in Greece and European Union. In addition it is provided as a service of free content under the web address: openmeteo.org where individuals can download or upload their data. The Information System for the Greek Nature "Filotis", contains biotopes and species of flora and fauna of Greece.

The development of the application is based on Python Computer Language and Django. Finally applications are providing geospatial data in a Web-GIS form by using free software GIS tools.

Speach video is here: http://www.vimeo.com/25340067

Enhydris is a database system for the storage and management of hydrological and meteorological data. It allows the storage and retrieval of raw data, processed time series, model parameters, curves and meta-information such as measurement stations overseers, instruments, events etc. The database is accessible through a web interface, which includes several data representation features such as tables, graphs and mapping capabilities. Data access is configurable to allow or to restrict user groups and/or privileged users to contribute or to download data. With these capabilities, Enhydris can be used either as a public repository of free data or as a fully secured – restricted system for data storage. Time series can be downloaded in plain text format that can be directly loaded to Hydrognomon (http://hydrognomon.org/), a free tool for analysis and processing of meteorological time series. Enhydris can optionally work in a distributed way. Many organisations can install one instance each, but an additional instance, common to all organisations, can be setup as a common portal. This additional instance can be configured to replicate data from the other databases, but without the space consuming time series, which it retrieves from the other databases on demand. A user can transparently use this portal to access the data of all participating organisations collectively. Enhydris is free software, available under the terms of the GNU General Public License version 3. It is developed with Python, Django, and C. Its modular design allows adding new features through the development of small applications. Enhydris is hosted by the Openmeteo project (http://openmeteo.org/), which aims to provide free tools and data.

The management of complex water resource systems requires system-wide decision-making and control, to fulfil multiple and often contradictory water uses and constraints, maximize benefits and simultaneously minimize risks or negative impacts. The rapidly developing area of hydroinformatics provides a variety of methodologies and tools that are suitable to solve specific computational problems and demands an integrated framework of model co-operation and linking. A holistic water resource systems analysis framework is presented, comprising conceptual and stochastic hydrological models, hydrosystem simulation models, and algorithms for both linear and non-linear optimization. The key concepts are the formulation of parsimonious structures that are consistent with the available data, the conjunctive representation of physical and man-made processes, the quantification of uncertainties and risks, the faithful description of system dynamics, and the use of optimization to provide rational results within multiple modelling scales. The hydrosystem schematization is based on a network-type representation of real-world components, including both physical (basins, rivers, aquifers, etc.) and artificial ones (reservoirs, aqueducts, boreholes, demand points, etc.). Hydrological inflows are synthetically generated, through a multivariate stochastic simulation scheme that preserves all essential statistical properties as well as the time- and space-correlations across different time scales. Hydrosystem operation is represented through a low-dimensional approach, based on generalized parametric rules, which are assigned to the main hydraulic controls. All water resource management aspects, including technical, economical and environmental data are effectively handled through a generalized graph optimization approach, which simultaneously preserves a detailed description of the related processes and computational efficiency. A global optimization approach, also implemented on a multiobjective basis, is used to provide suitable management policies and support decisions. Besides, the stochastic representation of all hydrosystem fluxes enables the assessment of results on a reliability basis.

The ODYSSEUS project (from the Greek acronym of its full title "Integrated Management of Hydrosystems in Conjunction with an Advanced Information System") aims at providing support to decision-makers towards integrated water resource management. The end-product comprises a system of co-operating software applications, suitable to handle a wide spectrum of water resources problems. The key methodological concepts are the holistic modelling approach, through the conjunctive representation of processes regarding water quantity and quality, man-made interventions, the parsimony of both input data requirements and system parameterization, the assessment of uncertainties and risks, and the extended use of optimization both for modelling (within various scales) and derivation of management policies. The core of the system is a relational database, named HYDRIA, for storing hydrosystem information; this includes geographical data, raw and processed time series, characteristics of measuring stations and facilities, and a variety of economic, environmental and water quality issues. The software architecture comprises various modules. HYDROGNOMON supports data retrieval, processing and visualization, and performs a variety of time series analysis tasks. HYDROGEIOS integrates a conjunctive hydrological model within a systems-oriented water management scheme, which estimates the available water resources at characteristic sites of the river basin and at the underlying aquifer. HYDRONOMEAS is the hydrosystem control module and locates optimal operation policies that minimize the risk and cost of decision-making. Additional modules are employed to prepare input data. DIPSOS estimates water needs for various uses (water supply, irrigation, industry, etc.), whereas RYPOS estimates pollutant loads from point and non-point sources, at a river basin scale. A last category comprises post-processing modules, for evaluating the proposed management policies by means of economical efficiency and water quality requirements. The latter include sophisticated models that estimate the space and time variation of specific pollutants within rivers (HERIDANOS) and lakes (LERNE), as well as simplified versions of them to be used within the hydrosystem simulation scheme. An interactive framework enables the exchange of data between the various modules, either off-line (through the database) or on-line, via appropriate design of common information structures. The whole system is in the final phase of its development and parts of it have been already tested in operational applications, by water authorities, organizations and consulting companies.

Hydronomeas is an operational software tool for the management of complex water resource systems. It is suitable to a wide range of hydrosystems, incorporating numerous physical, operational, administrative and environmental aspects of integrated river basin management. The mathematical framework follows the parameterisation-simulation-optimisation scheme; simulation is applied to faithfully represent the system operation, expressed in the form of parametric management rules, whereas optimisation is applied to derive the optimal management policy, which simultaneously minimises the risk and cost of decision-making. Hydrological inflows are synthetically generated, thus providing stochastic predictions for all system outputs (reservoir storages and withdrawals). Real economic criteria in addition to virtual costs are appropriately assigned to preserve the physical constraints and water use priorities, ensuring also the lowest-energy transportation path of water from the sources to the consumption. Hydronomeas is developed to operate within the framework of a decision support system, with a graphical user interface allowing users to create any configuration of hydrosystems consisting of reservoirs, groundwater facilities, pumping and hydropower stations, aqueduct networks, demand points, etc. Data structures are controlled by a database management module, whereas simulation is accompanied by a visualisation module. Results, including the optimal operating rule for each component of the system, the failure probability for each water use, the water and energy balance, as well as prediction curves for all hydrosystem fluxes, are presented in graphical plots. Saved scenarios can also be retrieved in the form of printable reports, which are automatically generated through the database management module. From year 2000, Hydronomeas is the central supporting tool of the Athens Water Supply and Sewage Company (EYDAP).

In complex hydrosystems, where natural processes are significantly affected by human interventions, a holistic modelling concept is required, to ensure a more faithful representation of mechanisms and hence a rational water resource management. An integrated scheme, comprising a conjunctive (i.e., surface and groundwater) hydrological model and a systems-oriented management model, was developed, based on a semi-distributed approach. Geographical input data include the river network, the sub-basins upstream of each river node and the aquifer discretization in the form of groundwater cells of arbitrary geometry. Additional layers of distributed geographical information, such as geology, land cover and terrain slope, are used to define the hydrological response units (HRUs); the latter are spatial components that correspond to areas of homogenous hydrological characteristics. On the other hand, input data for artificial components include reservoirs, water abstraction facilities, aqueducts and demand points. Dynamic input data consist of precipitation and potential evapotranspiration series, given at a sub-basin scale, and target demand series. Targets refer not only to water needs but also to various water management constraints, such as the preservation of minimum flows across the river network. Various modules are combined to represent the key processes in the watershed, i.e. (a) a conceptual soil moisture accounting model, with different parameters assigned to each HRU; (b) a groundwater model, based on a modified finite-volume numerical method; (c) a routing model, that implements the water movement across the river network; and (d) a water management model, inspired from the graph theory, which estimates the optimal hydrosystem fluxes, satisfying both physical constraints and target priorities and simultaneously minimising costs. Model outputs include discharges through the river network, spring flows, groundwater levels and water abstractions. The calibration employs an automatic procedure, based on multiple error criteria and a robust global optimisation algorithm. The model was applied to a meso-scale (~2000 km2) watershed in Greece, characterised by a complex physical system (a karstified background, with extended losses to the sea) and conflicting water uses. 10-year monthly discharge series from seven gauging stations were used to evaluate the model performance. Extended analysis proved that the exploitation of spatially distributed input information, in addition to the usage of a reasonable number of control variables that are fitted to multiple observed responses, ensures more realistic model parameters, also reducing prediction uncertainty, in comparison to earlier (both fully conceptual and fully distributed) approaches. Moreover, the incorporation of the water resource management scheme within the hydrological simulator makes the model suitable for operational use.

The water resource system of Greater Athens supplies water mainly for domestic and industrial use to the metropolitan area of Athens, Greece. The system consists of four reservoirs, groundwater resources, and a network of aqueducts and pumping stations. For the control of this system an integrated computational framework was developed named Hydronomeas, which implements the parameterisation-simulation-optimisation methodology. To allocate the water demand to the different system components, it uses a parametric operation rule thus keeping the number of control variables small. This parametric rule is embedded into a simulation-optimisation scheme. To perform each simulation step, the water resource system is transformed to a digraph, and the water conveyance problem is formulated as a typical transhipment problem, which can be solved by the network simplex algorithm. Global system objectives are incorporated in a performance measure, which is subsequently optimised using nonlinear optimisation methods. Users can specify multiple targets and constraints, give them priorities and set acceptable limits for the system reliability. Hydronomeas is currently used as the main decision support tool for the management of the water resource system of Athens.

The managent of water resources for the water supply of Athens via the software system Hydronomeas is summarised.

The design of the central database of HYDROGAEA is described. The database obeys the relational model and encompasses all data. The database consists of subsystems for the management of time series, the representation of the "real world", i.e., the geographical entities for measuring stations, cities, dams, conduits, lakes etc., and the mathematical models.

The subject of the report is the development of the software system HYDRONOMEAS, which is an operational tool for the management of complex water resource systems. The model is applicable to a wide range of hydrosystems, consisting of river branches, reservoirs, boreholes, pumping and hydropower stations, aqueduct networks, demand points, etc. After a general overview of the water resources management problem and a short presentation of some well-recognized decision support systems, we describe the theoretical background of the model, which implements the parameterisation-simulation-optimisation scheme. The former refers to the formulation of parametric control rules for the major infrastructures (reservoirs, boreholes), where the number of parameters is kept as low as possible. Simulation is applied to faithfully represent the processes. Specifically, real economic values in addition to virtual costs are assigned to network components to preserve the physical constraints and water use priorities, ensuring also the lowest-cost transportation path of water from the sources to the consumption. Finally, optimisation is applied to derive the optimal management policy on the basis of multiple performance criteria, thus ensuring simultaneous minimisation of the risk and cost of decision-making. Note that the modelling framework adopts a stochastic approach, providing predictions for all hydrosystem fluxes (storages, discharges, withdrawals) on the basis of synthetic scenarios of inflows. The last part of the report focus on the practical use of the model, as a stand-alone system as well as in co-operation with other modules developed within the ODYSSEUS research project.

The final report is part of Work Package 9 with title "Software development - Implementation of operational product" and includes three parts: (a) the conclusions from the installation of the prototype for the organisations of Karditsa and Kalymnos; (b) beta testing results, including the trial of software so its correctness, plenitude, subjects of safety and quality are checked and (c) the results of the inspection and evaluation of the final product by SOGREAH.

The present report refers to the Master Plan for water resources management for the area of Karditsa and was elaborated by NAMA's research team in cooperation with DEYA Karditsa and the National Technical University of Athens. This deliverable is part of Work Package 8 with title "Pilot Applications". The Pilot Applications aim to test and evaluate the product (from methodology and software efficiency viewpoints) on hydrosystems with totally different characteristics, in terms of their hydroclimatic regime, structure scale, and institutional and administrative framework of management. After the completion of the pilot applications, the product was re-examined at all levels (theoretical background, software design and implementation), before assuming its final form. This report will include the following main sections, according to the Technical Addendum of the Contract: (a) description of the study area, (b) description of the hydrosystem, (c) data and processing, (d) water needs assessment, (e) hydrological inflow assessment, (f) management of the hydrosystem, (g) simulation of quality parameters, (h) financial analysis and (i) conclusions and proposals.

Within the framework of the project entitled "Updating of the supervision and management of the Athens water supply resources system", a software system named Hydronomeas (version 3.2) has been developed to support the water resources management by EYDAP. The methodology implemented (parameterisation-simulation-optimisation) is based mainly on an original theoretical work. The mathematical framework used allows the allocation of the water demand to the different system components, keeping the number of control variables small. This enables the simulation and optimisation of complex hydrosystems such as the one in this project. For the simulation process with a given operating rule, multiple, competitive targets and constraints with specified priorities can be set, which are concerned among others, with the acceptable limits for the system reliability. In performing optimisation, users can select between three objective functions: a) the minimisation of the average failure, b) the minimisation of the overall average operational cost and c) the maximisation of the overall guaranteed yield of the system for a given acceptable failure level. The model uses as input historic hydrological time series or synthetic time series. The results are given in probabilistic terms and include the probability of failure for each target, the analytical water balance and the storage forecast for reservoirs and the flow balance and discharge forecast for aqueducts.

This software tool creates printable reports of the following two categories of information: (a) reports related to projects of the Water Resources Decision Support System Hydronomeas including a summary of the project, the input data and the main results of the calculations; (b) bulletins with reservoir storage variation and information concerning water consumption related to the water treatment plants of the Athens' water supply resources system (EYDAP). The Central Data Base Hydria supplies all data needed for the reports.

The methodology that was developed for the analysis of the water supply system of Athens, even though it was dictated by the special requirements of this particular system, has a broader character and a generalised orientation. In this respect, a series of publications in international scientific journals and communications in scientific conferences and workshops were done, so that the methodology becomes known to the international scientific community and raises its critique. These publications and communications are classified into two categories, with the fist one containing those referring to the core of the water supply system analysis, i.e., to the system optimisation based on the original methodology parameterisation-simulation-optimisation, and the second one containing those dealing with stochastic simulation and prediction of the hydrological inputs to the system. For a clear description and explanation of the methodology, the publications in scientific journals are reproduced in this volume and, for completeness, the summaries of the communications in conferences are included as well.

Within the frame of the project entitled "Updating of the supervision and management of the water supply resources system of Athens" five software systems that are developed are specified. The first one is the Geographical Information System, which aims to model and to supervise the hydrosystem of Athens. The second one is a network of hydrometeorological measuring stations in the catchments, which are linked to the water resource system of Athens are specified. The third system is used for the estimation of inflow and losses of the reservoirs, where the forth one estimates and predicts the water resources in the aquifers of the Viotikos Kifissos and Yliki region. Finally, the fifth system supports the management of water resources. The specifications described are used as a guideline for the development of the above systems.

The master plan for the operation of the Athens water resource system for the hydrological year 2000-20001 deals first with issues on the relations between the different organisations involved in the water supply of Athens, i.e., the Water Supply and Sewage Company of Athens, the Infrastructure Company for Water Supply and Sewage of Athens and a number of ministries. Projections of the water demand and the related water resources availability are studied in the form of future scenarios for which optimised system operating rules are drawn. The scenarios consider the phenomenon of the drought persistence as well as various possible emergency incidents. Operating cost estimates are also given together with elements on the environmental dimensions of the subject. Finally, estimates of the system safe yield and of the energy consumption for pumping water are presented in detail.

A software system named Hydronomeas (version 2.0) has been developed to support the water resources management policy of EYDAP. The methodology implemented (parametrization-simulation-optimization) is based mainly on an original theoretical work. The mathematical framework used allows the allocation of the water demand to the different system components, keeping the number of control variables small. This enables the simulation and optimisation of complex hydrosystems such as the water resource system of Athens. For the simulation process with a given operating rule, multiple, competitive targets and constraints with specified priorities can be set, which are concerned among others, with the acceptable limits for the system reliability. In performing optimisation, users can select between three objective functions: a) the minimisation of the average failure, b) the minimisation of the overall average operational cost and c) the maximisation of the overall firm yield of the system for an acceptable failure level. The model uses as input historic hydrological time series or synthetic time series. The results are given in probabilistic terms and include the probability of failure for each target, the analytical water balance for reservoirs, the flow balance for aqueducts, and economical data of the system operation.