Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

A date with distribution

Communities in a remote desert area of Oman can look forward to piped water supplies once a scheme to extract groundwater gets under way

The popular notion is that deserts are dry - devoid of water. But an exhaustive exploration and drilling programme, completed by Oman's Ministry of Water Resources (MWR), has revealed large quantities of good quality groundwater at Al Masarrat, which lies to the west of the Al Hajer Mountains, some 40km into the desert.

The mountain region is well populated by the standards of the area. Ibri, the largest settlement and the regional capital has a population of around 42,000.

This is predicted to rise to more than 108,000 by 2029, the project design year. Three other towns in the area boast populations of between 8,000 and 11,000 and there are eight villages.

Agriculture is the main business and the area is famous for its dates. Currently most homes and businesses in the area rely on tanker delivered water - Ibri has a small private piped water scheme - while the date farmers extract groundwater and a little surface water from the wadis.

Each date tree requires something like 100 litres of water a day.

Annual rainfall is around 75mm rising to as much as 200mm over the mountains, occasionally even causing flash floods. Runoff water flows along the wadis and eventually recharges the Upper Fars formation which underlies the area, creating very large bodies of fresh groundwater.

The MWR investigation was carried out in two phases. The first was a regional exploration while the second, carried out between August 1995 and May 1996, concentrated on two large wadi systems; Wadi A'Bukraba and Wadi Al Ayn.

The exploration and assessment stage was managed by MWR's Mike Brook and the subsequent development of the aquifer by MWR director general of water resources management Saif Al Shaqsi.

It was decided to exploit the groundwater resources which provide the source of the Al Masarrat scheme. Each will have a collection and delivery system to supply water to the towns and villages in the area - Al Ayn being the larger of the two.

The scheme has been designed by consultant Mott MacDonald through its local company Mott MacDonald LLC under a ú996,000 ($1.3m) contract awarded by the MWR.

Design work on the transmission system was finished by mid-November 1999, which enabled ruler, Sultan Quaboos bin Said, to announce that the scheme was ready to go out to tender at Oman's National Day celebrations in Ibri. Design work for the distribution system began immediately afterwards and this work went out to a separate tender in September 2000.

The relatively tight deadline put a fair degree of pressure on the consultant and the Mott MacDonald office in Oman was heavily supported by the company's Cambridge, UK, office.

The available mapping was 'not ideal', says Mott's Andrew Wedgner, so the first step was to commission an aerial survey from Northern Ireland based company BKS. With stereo effect photographs and 1:2000 scale maps of the area the routes for the pipelines were identified in outline, and the strips of land modelled in AutoCAD 14 format.

A full environmental impact assessment was also carried out by Mott's Catherine Sanders, which revealed a number of sites of archeological significance.

The smaller wellfield at A'Bukraba will supply the town of Dank and a number of small settlements. Output here is initially calculated at 9.1M litre/ day rising to 15.5M litre/d by 2029.

The system extending from the Al Ayn field is more complex, running first to Ibri then to Khadil from where it branches out into two lines supplying Yanqul and Miskin up in the mountains. The wells will be some 140m deep. This system is designed to produce 39.2M litre/day, rising to 87.4M llitre/day in 2029.

In addition to 215km of ductile iron transmission pipeline and 431km of distribution pipeline, the scheme includes 11 service reservoirs and 13 water towers.

There will also be four main pumping stations, two secondary pumping stations and five standby electricity generation units.

Reservoir sites were chosen first by using the stereo photographs and then on site inspection. Most of them are up in the hills and could only be reached on foot during the initial survey.

This is arduous work given Oman's high temperatures, but Wedgner clearly relished the task. 'This is what being an engineer is about, ' he remembers thinking.

Most of the reservoirs are built on outcrops of limestone rock and vary in capacity between 0.4M litre and 22M litre. They are completely enclosed and embedded in embankments faced with limestone. The roofs are finished with a layer of sprayed polyurethane membrane and solar protection. The interiors are fitted with plastic baffle curtains to avoid dead spots.

The water towers have been designed to look like traditional Omani watchtowers, the tallest around 40m high. Construction of the crenellated towers is complex as they are stepped back at each storey.

Siting reservoirs and water towers had to take account of the archeological remains. The area is well known for its beehive tombs as well as for cairn burials. The pipeline has had to be rerouted at several points to avoid groups of cairns, but at Ibri, the problem was more complex. The only possible site for the reservoir was effectively divided by some 3000 year old remains. The site had to be split into two with a connecting 10m wide corridor.

Tanker filling points have been included in the design at 15 locations, since some of the settlements are so small as to make a direct water supply uneconomic.

The water is of good quality and meets World Health Organisation standards but will be chlorinated and fluoridated however, using gaseous chlorine and hydrofluorsilicic acid.

Mott initially investigated the feasibility of on-site power generation, and Wedgner says it was a close thing. But in the end the decision went to tapping into the district electrical supply, although there will be stand-by power plants at the two well sites at Ibri and at Khadil.

Ibri will the location for the scheme's monitoring station and control centre, fitted with the country's first systemwide SCADA system for a water supply project.

Construction has already begun on the transmission system, after contract award to Societe Egyptienne d'Entreprises in May. Invitation to tender for the distribution system went out in late September. The scheme is expected to be up and running in March 2002.

Mott MacDonald has been awarded a second contract worth around ú740,000 for construction supervision, continuing its involvement from inception to the moment when water flows into people's homes.

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.