Modelling, Design and Construction Monitoring of Neckartal Dam, Namibia

Modelling, Design and Construction Monitoring of Neckartal Dam, Namibia

Author: G.L. Coetzee, S.J. van Vuuren
Conference: AFRICA 2019
Date: April 2-4, 2019

Neckartal is the largest dam in Namibia, with a full supply volume of 853 x 106m3, exceeding the volume of what was previously the largest dam, Hardap, by a factor of three. Projects of this magnitude need innovative construction technology to be implemented successfully. In the case of Neckartal, a special challenge was its isolated location in the arid climate of southern Namibia, with irregular, high peak runoffs. During the design of the dam, two physical models were built. Results from the physical model testing were used to improve the safety of the spillway and reduce potential scour erosion downstream. Throughout the construction of the dam, innovative techniques were used, which are described in this paper.

In the early 20th century, German colonialists identified the site of the Neckartal dam, in the arid southern Karas region of Namibia. The Neckartal Dam and Phase 1 Bulk Water Supply Project is on the Fish river, about 41 km west of Keetmanshoop and some 22 km north of Seeheim. The dam has a catchment area of 45 365 km2 and a mean annual runoff (MAR) of 397 x 106m3/year, categorizing the storage volume of the dam as 2.14 of the MAR. At the time of Namibia's independence in 1990, planning of the dam was initiated, although a provisional design has been undertaken in the 1960s. The Namibian Ministry of Agriculture, Water and Forestry (MAWF), also referred to as the client, decided to implement the project with the aim of improving employment and aiding the long-term sustainable economic development of the Karas region. The project envisages elevating the agricultural development of the region with 1960 ha of irrigable farmland to be developed during Phase 1, which may be further expanded to 5000 ha.

The final design of the structure consisted of a 65 .5 m-high, curved, stepped, gravity, roller compacted concrete (RCC) wall with an uncontrolled ogee spillway, consisting of a lower spillway section and a higher spillway raised by 2.4 m. There is a multi-level intake structure with eight DN1600 and two DN3000 intakes. Other features of the dam include a spillway chute on the right bank to prevent flood erosion of the downstream foundation, two internal galleries, a control room and outlet works, together with the machine hall and sleeve valve house. With a recommended design discharge (RDD) of 9060 m3/s and a safety evaluation flood (SEF) of 21 480 m3/s, the spillway length is significant and necessitates the widest possible spill area to reduce the unit discharge rate to an acceptable criterion of less than 30 m3/s/m.

 

Download the full technical paper.

Download

Recent Insights

September 2025
Laying Groundwork for Future Mining: Infrastructure Support by Knight Piésold
September 2025
Challenges of Tailings Transport Pumping Systems in Negative Static Head Applications
September 2025
Hydraulic Evaluation of Tailings Transport Systems in Mountainous Terrain: Density Wave Analysis
September 2025
The Role of Rheology Tests in the Design and Operation of Long-Distance Slurry Transport Systems
August 2025
Safe Dams, Straight Talk: The Knight Piésold Difference
July 2025
Knight Piésold Zambia: Building a Future of Engineering Brilliance and Local Empowerment
July 2025
Water Engineering for Modern Mining: Bridging Mining with Sustainability
June 2025
The Essence of Material Compatibility in Advanced Barrier Systems of Existing TSFs
June 2025
Inverted Barriers in Tailings Storage Facilities: Lessons Learnt
June 2025
Prioritizing the Mitigation of Legacy Geomechanical Mine Hazards Using a Risk-Based Approach
May 2025
Knight Piésold: Sustainable Projects in DRC Through Baseline Studies
April 2025
Advancements in Geotechnical Investigations for the Characterisation of Upstream Tailings Dams in SA
November 2024
Knight Piésold: Commitment to African Excellence
November 2024
Design of a Co-disposal Facility for Thickened Tailings and Potentially Acid-generating Waste Rock
November 2024
Compaction Sensitivity in Tailings Stack Infiltration Modeling: Unsaturated Properties Uncertainty Analysis
November 2024
Volumes of Dam Material Mobilized by Erosion During Tailings Dam Failure Events
October 2024
Estudio de rotura de una presa de jales en la zona centro-norte de México
September 2024
Grouting to Reduce Seepage at Neckartal Dam, Namibia
September 2024
Influence of Pre-Existing Mobilized Zones on B3 Cave Propagation and Initial Subsidence at the New Afton Mine
September 2024
Importance of Indigenous Community Engagement related to ARD/ML and Long-Term Water Quality