The wadi dayqah drinking water dam in oman – Lessons learned from planning, construction and operation

The Sultanate of Oman is in one of the world’s semi-arid regions. The Wadi Dayqah project involved creating a 75 m-high roller-compacted concrete (RCC) dam, a 50 m-high rock-fill saddle dam, a 100 km-long water pipeline and a water treatment works. Sizing the spillway over the RCC dam and sealing the sandstone bedrock below the dam were the biggest challenges during planning work, alongside high day-time and night-time temperatures of 45 °C to 35 °C in summer. During construction work, flow exceeded 10,000 m³/s in the wadi during a tropical cyclone in June 2007. The spillway had only been designed to handle 7,500 m³/s so it had to be adjusted to reflect the new conditions. During the first impoundment, seepage occurred on the right flank of the rock-fill dam, which would have jeopardised the dam’s structural safety in the long run. Consequently, the bedrock under the right valley flank had to be resealed.