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Although you might think that a water storage dam would probably be an anachronism in the Persian Gulf, sufficient water does fall in the mountainous areas of the Arabian Peninsula to make water storage seem to be a viable option. Several small dams were built on Al Jabal al Akhdar during the 1990s to feed domestic water supply to villages and to irrigate agriculture, particularly in regions where water supply from traditional springs had dwindled.

But at what point does the benefit of building such structures become overtaken by the cost?

The projected dam across Wadi Dayqah - now spelt Dhaiqa in the Omani press - might just be an example. A pre-tender contract was announced in August this year for the first phase of water supply to the wilayat of Qurayyat, sometimes spelt as Quriyat. Apparently, the Ministry of Regional Municipalities, Environment and Water Resources had already "finalised the detailed designs and the tender documents for the implementation of the dam and its facilities, while work was under way on preparing the maps of water supplies for Muscat and Qurayyat." Annoyingly, no mention was made of whether this work had been undertaken totally in-house or with the help of commercial engineering consultants.

Wadi Dayqah lies 60 km southeast of Muscat. The "390-metre-long storage dam with a height of 73.6 metres and a 100 million-cubic-metre storage capacity would provide about 35 million cubic metres of water a year: around 10 million cubic metres for villages down the wadi stream for agricultural purposes and around 5.7 and 19.3 million cubic meters for drinking and domestic purposes in Qurayat and Muscat Governorate consecutively" (sic). Oman Observer, 19th November 2005.

I was working in the Ministry of Water Resources in Muscat at the time when the feasibility of this dam was being investigated and also when the notion of building it first looked like becoming a reality. Then, there was some speculation that the site could also attract tourism facilities and water sports.

Well, the hydrological engineer leading the investigation concluded that the benefits of building the dam would not outweigh the costs. Although water flow in Wadi Dayqah is perennial in its upper and middle reaches, quantities of water are not guaranteed from year to year. When it does rain, the water arrives in torrents. Oman has some of the highest possible flood maxima in the world. This means huge quantities of alluvium, not just fine-grained clays, silts and sands, but boulders and rocks which could rapidly fill a confined space. Wadi Dayqah gorge transects the highly permeable, karstic Tertiary limestone over much of its length. A lot of grout would be needed to seal the basin from leakage.

Not to mention the socioeconomic impact on the villages downstream. Never mind. Officials from the ministry popped along to the Wali's office in Quriyat in early November to tell the inhabitants what a marvellous asset this dam would be. How could it be otherwise when the ministry had calculated that only 10% of the water flow benefited agriculture while the rest was lost to the sea. Actually, I wonder if anyone had measured that, or apportioned the water losses along the course of the wadi.

Don Davison, a pioneering hydrogeologist in Oman, discovered very many submarine freshwater springs beneath the cliffs just off the coast for several kilometres east of the Daghmar Plain where Wadi Dayqah meets the sea. This points to groundwater feeding off the flow from Wadi Dayqah moving underground directly towards the sea and nowhere in the direction of Quriyat. His findings were never published and a seminal study that he wrote on the Springs of Oman disappeared.

Five years or so from now, we shall find out whether it was worth losing this magnificent vista, all the more poignant in view of His Majesty Sultan Qaboos' desire to conserve Oman's environment.

Only in March this year, passengers on the Queen Elizabeth 2, calling in at Port Sultan Qaboos in Muscat, were offered an excursion to see Mazara Village and the Wadi Dayqah gorge. Khaleej Times, 28th March 2005.

Added 28th April 2006. Two days ago, the Omani English-language press announced that work on the Wadi Dayqah dam and a series of saddle dams would begin next year, with completion expected in 2009. "Several leading Omani construction firms are among 13 companies that have submitted documents to prequalify for this second stage Water Supply Works contract. In the fray are Consolidated Contractors Co, Gannon Dunkerley & Co, China Gezhouba Water & Power, PC International, Galfar Engineering, Gulf Petrochemical Services, Larsen & Toubro (Oman), Gammon India Limited, Hasan bin Juma bin Backer Trading & Contracting, Societe Egyptienne D’enterprises, Al Husam General Contracting, and Nagarjuna Construction."

I circulated this information to colleagues who worked on evaluation of this project in the 1990s. Here are their comments in return.

"I really wonder whether it's technically viable, but a lot of money will certainly be made. It was a lovely wadi with many happy memories for us all, but perhaps a large reservoir will offer environmental compensation. It makes one feel that we were there at the best time!"

"Hanging water out to dry."