Hydraulic Modeling Enables Taming of the Ebro

Zaragoza, Spain, models its water and wastewater networks in InfoWorks WS and CS, allowing for better predictive rehabilitation and management as well as reduced flooding risk.

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By Alfonso Narvaiza

Zaragoza, Spain, models its water and wastewater networks
in InfoWorks WS and CS, allowing for better predictive
rehabilitation and management as well as reduced flooding risk.

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Zaragoza, Spain
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As new challenges to the water and wastewater sectors arise, such as a need to meet sustainability ideals and innovation targets while providing solutions to the water crisis and additional pressures posed by population increases, new tools are increasingly needed to ensure optimum technical and environmental solutions are chosen.

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The Zaragoza Council spent much of 2008 working on the International Exposition — with a special focus on “Water and Sustainable Development” — and also on its less well-known role of operating its water and wastewater networks. Faced with the above issues, the council, led by its Networks Operations Department, began an ambitious project this year to provide the best possible solutions by using the best tools to enable them to understand these assets in detail and make the right decisions for any future eventuality. Zaragoza is the fifth largest city in Spain, with 650,000 inhabitants. Located midway between Barcelona and Madrid, Valencia and Bilbao, it’s in the northeast of the country in the valley of the Ebro River, the biggest river on the Iberian Peninsula. The tools the city has chosen to help it meet the challenges are Wallingford Software’s InfoWorks CS and WS, solutions that enable simulation of both hydraulics and water quality of water and wastewater networks. The solutions allow Zaragoza to have a unique view of its assets and their performance. They allow global decisions to be taken to optimize the networks and determine how future elements should be constructed to meet predicted needs. In the short term, the models won’t only be used to design improvements to the networks, but also to manage them. The modeling and diagnostic work for the wastewater network is nearly complete. The water supply network is now migrating from existing GIS and EPANET models to InfoWorks WS.

The Wastewater Network

All the trunk sewer network has been modeled, including 1,066 km of pipes, 28,232 manholes, 80 spillways, 14 pumping stations and two tanks. The main system comprises 170 km of trunk sewers of diameters over 1,000 mm, 280 km of secondary pipelines and 600 km of smaller pipes in total catchment area of 8,000 hectares. The network is an almost-wholly combined stormwater and wastewater system, though in new development areas separate systems have been constructed. It is mainly organized as two main trunk sewers running on both banks of the Ebro river and joining together on the eastern margins of Zaragoza, from where flows go to Cartuja, to the southeast of the council’s area. These trunks sewers collect wastewater from the urban centre and some outlying areas. The Almozara treatment works receives flows from a small area in the centre of the city and from urban and industrial areas on the city’s Logroño road. The majority of the urban catchments are highly-populated areas, but some contain large parks, meaning the networks there should be able to drain a high volume of runoff. In rural areas and those with detached houses, most of the runoff drains directly to “soakaways” — temporary retention areas. The model was calibrated using measured data on the amount of water found in the network during known rainfall events. With this calibrated model, simulations were run for two-, five- and 10-year return periods and for different rainfall durations. The major problems highlighted by InfoWorks matched exactly with areas where flooding is known to occur periodically. In addition, the modeling software has allowed the council to understand why the problems occur and what the best solutions are. Results showed flooding was occurring because the diameter of the pipes was insufficient to contain the flows. At some points also adverse slopes or bottlenecks were occurring, often many metres downstream from where flooding was happening. The solutions proposed cover a range of options, including increasing the current diameter of pipes, rebuilding some spillways, constructing storm tanks, optimising pumping stations or connecting subcatchments via new pumps.

The Water Network

The 1,250-km water network contains five pumping stations and 12 tanks or reservoirs that serve the entire area by gravity, apart from the Canteras rising main which uses automated pumps that regulate system pressure. The process of importing data from EPANET and the city’s GIS system to InfoWorks WS has begun very successfully and has proved very easy, as InfoWorks WS is able to import the data directly. The goal is to model the entire water network in InfoWorks WS to exploit its potential to optimize network management, improve service quality, water quality, operational costs, etc.

Software

The InfoWorks suite of solutions allows analysis of water networks, wastewater networks and rivers, and also their management and operation. It’s a global solution that integrates detailed company plans and models.. Not only does the software undertake hydraulic and hydrological calculations in real time, it also models water quality and sedimentation and determines the economic optimisation of network operations, connections to SCADA and telemetry, etc. The engine is fully embedded in a GIS (ArcView/ArcMap or MapInfo), the master database can be in Access, Oracle or SQL, and solutions can import and export from and to other software solutions including AutoCAD, Excel, Access, MSWord, ArcView/ArcMap, and MapInfo. InfoWorks CS and RS also can model surface water flows thanks to the 2D module. Flooding predictions and warnings, for both rural and urban areas, can be undertaken using FloodWorks. InfoWorks surprised the city not only with its versatility, user-friendly interface and productivity, but also because its engine proved more advanced than other software evaluated. What really struck Zaragoza about the modeling system was its vast capability and fast calculations, as well as the robustness of the software.

Conclusion

Spain’s New Water Policy, which came into force following enactment of the EU Water Directive (2000/60/CE) at the end of 2003, created a requirement to manage water sustainably. The criteria for this are sustainable environmental, economic and social actions, and in this area the InfoWorks software is proving extremely useful in helping to achieve targets. The council was very satisfied with results obtained, principally in optimizing the hydraulic performance of the networks, with the solutions’ achievements including avoiding spills to the river and enabling creation of the new infrastructure plan.

Acknowledgment:

The author would like to thank Wallingford Software for its assistance on this article. Contact: +44 (0)1491 824 777, sales@wallingfordsoftware.com or www.wallingfordsoftware.com

Author’s Note:

Alfonso Narvaiza is manager of Zaragoza Council’s water and waste water networks operations.

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