Articles & Case Studies

Alqueva Irrigation Plan opens new opportunities for rural communities in Portugal

Posted: Friday 12th November 2010

Authors: José Carlos Saião, EDIA and Nuno Aleixo, KSB Portugal

The Alentejo region in the southern half of Portugal at 27,000 sq/km covers almost one third of the country and has a population approximately 500,000 inhabitants. However, it has not yet managed to develop its full potential. Whilst it is relatively arid, it is a beautiful area with rich potential for the diversification of agriculture and developing tourism. These attributes have long been recognised by the Portuguese government, but until the past decade it has always been the lack of a constant water supply that has held back private investment.

This is now rapidly changing as the damming of the Guadiana River has helped to create the largest artificial lake in Europe and is enabling the implementation of a highly ambitious irrigation project. Called the Alqueva Multipurpose Project (AMP) and managed by EDIA (Alqueva Development & Infrastructure Company), the main objectives are to progressively change the crop model, produce electricity, provide a guaranteed supply of water to the population and industry, develop tourism, stimulate regional employment and combat the potential problems of desertification and climate change using irrigation.

The dam gates at Alqueva at the southern-most end of the reservoir were closed in 2002 and the reservoir started filling up to a position where today it covers an area of 250km², a length of around 83km and a holding total capacity of 4150hm³ of which 3150hm³ are usable during regular operation. Between 2002 and 2010, the irrigation plan has involved the construction of 17 smaller reservoirs, nine of which are embankment damns, and when fully completed in 2013 there will be 680km of primary irrigation channels and 4400km of secondary and tertiary irrigation channels. Moving such large volumes of water across this extensive area demands a considerable pumping infrastructure.

A large part of the land that is scheduled for irrigation is in the Sado Basin, so a water transfer system is being established between the Guadiana and Sado rivers. This network is divided into three sub-systems: Alqueva, comprising 59,690 ha irrigated by the Alqueva reservoir; Pedrogão, comprising 29,578 ha irrigated by the Pedrogão reservoir; and the Ardila, comprising 20,935 ha also irrigated by the Pedrogão reservoir. The primary network features several pumping station to deliver water to each system and to the reservoirs and in each system there are several irrigation (secondary network) blocks providing water to farmers.

International pump manufacturer KSB became involved in the project at a very early stage due to its strong local presence in Portugal and its well respected name in the water supply industry. Having a sales team of highly technical and experienced people, KSB Portugal is regularly requested by engineering companies to support them, which happened again with this project. At the half-way stage of the project, more than 100 pumps have been supplied for the primary and secondary water supply networks.

The mix of KSB pumps has in the main comprised axially split Omega and RDLO units, with the larger RDLO pumps being used in pumping stations along the primary network. In addition, a small number of MTC V vertical barrel casing multi-stage pumps have been supplied.

With energy efficiency being one of the prime factors in the pumps specification, KSB tested all the pumps in accordance with ISO 9906/1. The axially split, single stage volute casing Omega pump features a double entry radial impeller and is ideally suited to the requirement of the pumping stations along the secondary network as it provides the best duty point and gives operating efficiency levels of above 86%. The interior of the pump has been specifically designed to transport water with the minimum of flow resistance, a factor that also contributes to energy savings and reduced life-cycle costs.

A characteristic of the Omega is its versatility, which is reflected in the large number of hydraulic selection charts, combinations of materials and shaft seal designs, installation options and flange variants. The drive may be positioned on both the left and right of the pump without additional parts or modifications to the casing being necessary.

The RDLO axially split volute, single-stage casing pump can achieve efficiency levels of above 90% and like the smaller Omega features a double entry radial impeller and has been designed for both horizontal and vertical installations. All rotor parts are self-aligning so there is no additional work required for pump alignment, which makes assembly and installation fast and straightforward.

All the Omega and RDLO pumps for the AMP have been supplied with bearings, temperature and vibration sensors, so that the pumping station operators can evaluate pump performance in real time.

KSB was able to demonstrate very early on in the project that it was a committed supplier and partner when it was called upon to manufacture and deliver 11 Omega pumps with the highest efficiency for the Marmelo pumping station within a very short and an exacting time frame. By demonstrating both to EDIA and the electrical and mechanical contractor building the pumping station that it could fulfil their technical and delivery requirements, KSB won the contracts for the next two pumping stations at Lagoa Vermela and Monte Branco.

Having supplied 33 pumps in total for the first three pumping stations gave the contractors involved in the subsequent projects the reassurance that KSB could be relied upon to fully comply with EDIA’s requirements and the project’s tight delivery times. This guaranteed to the contractor and the end-user that the installation, commissioning and exploitation would run smoothly and on time.

In 2007, 2008 and 2009 KSB supplied further Omega pumps for the Monte Novo and Cuba West pumping stations, RDLO pumps for the stations at Brinches, Torre do Lóbio and the Serpa Hydropower plant and Omega and MTC V pumps in the stations at Orada-Amoreira, Torro do Lóbio, Brinches Sul, Brinches Norte, Ferreira, Figueirinha, Valbom and Alfundão.

In order to ensure optimum use of the water throughout all the irrigation channels, standpoints are located at strategic positions for farmers and all of these are connected by telemetry to the local pumping station. Once a valve has been opened by the farmer to release water, this facility makes it possible to measure the volume of water being used throughout the day and to calculate the flow demand in order to control the pumps efficiently. A sophisticated software program has been designed that automatically adjusts pressures and flows on the pumps in accordance with demand. The pumps are also closely monitored by engineers via remote PCs.

The level of operation to which the Omega and RDLO pumps are subjected varies according to the seasons. During the summer months demand for water is considerably higher than at other times of the year, resulting in the pumps running for long periods during the day. However, when demand is low many of the pumping stations employ smaller ‘jockey’ pumps simply to maintain pressure in the networks and water levels in the dams as this is more efficient. When demand increases beyond the capacity of the smaller pumps, the larger KSB pumps will automatically take over. In order to minimise pump wear and optimise life-cycle costs, all the pumping stations operate a programme that automatically switches demand between the pumps.

The competitive edge that has enabled KSB to secure such a large size of the pump contracts lies not just in the proven capability of its products in the water supply industry around the world, but also its ability to provide high level and experienced local technical support from the engineering phase to the installation of the pumps and continuing servicing facilities post commissioning. As a result, KSB has set a benchmark and reference point that contractors must meet when tendering for this project.

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