Omdel Dam, situated near the town of Hentiesbaai, Namibia is a 32m high Clay-Core with Sandy Shoulders Dam (CC) with a 650m crest length.

The Central Namib Water Scheme supplies Swakopmund, Walvis Bay, Rössing, Arandis anda couple of smaller towns. Omdel draws its water from underground, the Kuiseb River as well as the Omaruru River delta. Water delivery from the Omdel is currently 8.5 million m³ per year; however, dam was originally built for 3.5 million m³.

Like most westward flowing rivers, the Omaruru carries a high silt load and during the design phase it was proposed that the incoming waters be contained for a time period, allowing the silt to settle out. The clean water could then be released into the infiltration areas.

The footprint of the wall stands on variable unconsolidated alluvium, thus large amount of seepage can be expected. Clever design features of this particular dam wall limit this seepage to prevent destabilization of the foundation. Furthermore, there are various drains to prevent seepage from destroying the clay core, when the dam is fully Impounded. These drains prevent internal water pressure build-up and the shoulders are covered with rock to prevent wind and wave erosion.

Omdel Dam Instrumentation consists of the following:

• Vibrating Wire Piezometers in the Clay Core and foundation measuring pore pressure.
• Standpipe Piezometers for measuring water table.

Instruments installed in and around the Dam Embankment are intended to monitor:

• Pore pressure build in the clay and foundation;
• Seepage

Installed Instruments Specification:

Piezometers (Clay Core/Foundation)

• Geokon Vibrating Wire Model 4500S

Standpipe ( Downstream from Embankment)

• Geotechnical Instrumentation Casagrande Standpipes

Designers: Department of Water Affairs

Consulting Engineers: Department of Water Affairs

Contractors: Department of Water Affairs