**1. Introduction**

42 Current Issues of Water Management

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In recent years a major effort has been done to make water quality modelling tools available for water resources management at a river basin scale. The European water framework directive clear states that these tools must be used in making the diagnostic of surface water bodies water quality status and to anticipate the impact of measures to be implemented in order to achieve a good ecological status by 2015 in European waters (European Commission 2000; Rekolainen 2003; Horn et al. 2004; Ravesteijn & Kroesen 2007; Volk et al. 2008).

In order to make modelling tools usable by all the actors enrolled in water resources management process at river basins, these tools must be simple, user-friendly and robust. Water managers have shown strong interest in the integration of model tools throughout the use of graphical interfaces in their activities (Borowski & Hare 2007). These tools must be able to establish water management scenarios but it is well known that water managers have lack of time for training in the use of complex systems. Also software and hardware costs appear to be an important constrain in implementing these tools.

Several solutions are being implemented throughout European countries, resulting from the development and integration of different software packages using different integration technologies (Dudley et al. 2005, Berlekamp et al. 2007, De Kok et al. 2009).

This chapter presents a hydroinformatic environment (Price, 2000) specifically designed for a Portuguese north-western river basin (river Cávado) in order to define, simulate and analyse hydrodynamics and water quality management scenarios – the ODeCav System. The software solution was designed to be operated in a web environment, taking advantage of the integration capabilities of this software environment and the user friendliness of web interfaces. It is composed of the following main components: water monitoring data-bases, hydrodynamics and water quality river models, and reports facilities for the presentation of output results. The applicability of this hydroinformatic environment is exposed in the study of waste water treatment plants (WWTP) discharges impacts on the river water quality for different river flow regimes.

Web-Based Decision Support Framework for

such as degradation of organic matter.

masses mixing conditions.

this purpose.

(Figure 1).

Water Resources Management at River Basin Scale 45

framework, as much inclusive as possible that cover simple water quality processes, such as the modeling of accidental releases of conservative pollutants, or more complex processes,

For problems involving conservative substances it is only considered the transport of the substance in the water through advection and diffusion. The evaluation of the extensions and durations of accidental discharge can be carried out recurring to a model in which the accidental discharge is modeled by a conservative substance. In addition to the cases of accidental discharge, these simple models also have practical interest to quantify the residence times and to analyze the effect of different hydrodynamic conditions in the water

The majority of elements and substances in aquatic environments have reactions with other elements and/or substances, resulting in their transformation (decrease or increase in concentration). Bacterial contamination arising from discharges of domestic wastewater or diffuse sources, for example, can be modeled by taking up a 1st-order decay law. The behavior of many other substances (or species) can be approximated by considering the decay or growth of a second order, such as biochemical oxygen demand (BOD) or algae. The reaction coefficients should be established mainly through the available field data or laboratory tests. Dissolved oxygen (DO) is a common environmental element used to characterize the water quality in water systems. The analysis of the impact caused by discharges with a high concentration of organic matter may be made to quantify the effects in terms of variations in concentrations of dissolved oxygen in the water column, due to the decomposition of organic matter contained in wastewater discharges. The water quality processes library used in this work is one of the most complete for surface water quality modeling and includes all the relevant processes allowing the establishment of either

complex water quality processes or simple ones depending on data availability.

The developed technological platform is mainly based on a database system and a set of hydrological, hydrodynamic and water quality models, operated using web interfaces. It comprises functionalities for query and analysis of the river network (information system), hydrodynamic and water quality models operation (modelling system), and results analysis (analysis system). Besides this, the platform provides the following additional services: user's management, document management and monitoring data store and display. The user's management service allows restricting or not the access to various content, as well as the permissions to run/execute or to view/consult/query the simulations results. The document management service allows the users to perform simple tasks, such as publication of papers and upload/download of work documents. The monitoring data functionalities provides a framework for gauge and water quality stations installed in the river basin, allowing its analysis, validation, and integration using a specifically designed database for

The website responsible for the system interaction with the end users is divided into four main sections that allow access to the features mentioned above: Project, Information, Modelling and Analysis. These sub-menus are the main options from the navigation menu

**2.2 Web-based hydroinformatic environment** 
