Repair and Improvement of Nwamankena Dam
Nwamankena Dam is located along the non-perennial Metsemola River, approximately 17 km west of Giyani in The Limpopo Province. It is situated adjacently to two villages of Nwamankena East and West in Ward 8 of Greater Giyani Municipality, within the Mopani district. The dam is an earth-fill dam, constructed mainly for stock watering purposes. Its original construction involved scooping of naturally-occurring top soil underlying weathered bedrockwhich was used to construct a low wall with moderately steep sides. The dam wall included an unlined overflow canal at the southern end tunnel of the wall which was excavated into weathered bedrock. The dam serves six villages, namely:Dingamazi; Ximange; Skhiming; Basani; Silawa and N’wamankena.
Causes of Dam Failure
The dam was built with an inadequate overflow spillway facility, resulting in overtopping during flood events. The combination of erodability of the construction material and the unevenness of the dam wall across its span, culminated in erosion of the crest, particularly around the central part. The vulnerable dam wall suffered catastrophic breaches of the left embankment on four occasions, the last being in 2005. Thereafter, the dam could no longer hold water. The erosion caused a gully downstream, which required rehabilitation.
The Repair and Improvement of the Dam Wall
The Department of Water Affairs felt the need to restore the dam wall so as to enable the local community to get water for their livestock and open up new opportunities. Following successful planning, geo-hydrological assessment, and design and procurement processes for the necessary service providers, the project was launched on the 1st of December 2010 in Nwamankena Village. The event was witnessed by all stakeholders including the two Municipalities of Giyani and Mopani; government departments including the Department of Agriculture; the Department of Water Affairs; Local community members and their local leadership; service providers including EVN Africa, BS Civils River port Trading, JV and The Mvula Trust. On the same day, the site was handed over to the contractor and the physical construction work started in earnest during the first week of December 2010. Physical completion was finally achieved in April 2011.
Following the completion of the repairs and improvement work on the dam wall, the primary objective of the intervention has been fulfilled thus far. The dam wall is once again fully restored and improved in terms of structural resilience, flood management and storage capacity. The dam wall can now impound an excess of 395 000 cubic metres of water, which will address the dire need for a perennial source of water for livestock watering, not only for Nwamankena village, but also for the neighbouring villages of Dingamazi; Ximange; Skhiming; Basani and Silawa.
While the water may not sufficiently prove fit for domestic use due to the fact that the catchment area is small (i.e. about 15 square kilometres)and the dam is located in a water-stressed area which receives low rainfall, the yield shall be assessed with a view to establish whether a nominal quality of water can be drawn, purified and piped to the beneficiary village in the future.
The department of Water Affairs appointed The Mvula Trust to be their implementing Agent (AI) on the project, being responsible for overall project steering and coordination. EVN Africa was appointed as the contractor. Three committees, namely The Steering Committee, Technical Committee and Labour Forum, were appointed to provide technical and institutional guidance and advisory services throughout the construction phase.
The project created temporary and medium-term employment opportunities for the local youths which translated to temporary income relief to the unemployed, as well as contributing to the objectives of the Expanded Publish Works Programme (EPWP). The availability of water in the dam will result in livestock being driven shorter distances to the watering point, reduction in drudgery on the village/s, and will increase available time that can be deployed for other socio-economic activities. The availability of water will also mean that livestock production will experience a boom,not only because of the increased supply of water but also because of improved pastures around the perimeter of the dam. The dam, being a common community asset, will also boost community cohesion as people will interact more amongst themselves and with stakeholders.
The dammed water presents a multiplicity of socio-economic opportunities for the locals. The dam can provide limited amounts of pottable water if some packaged plants are installed and used during the first half of the year when the water levels are high. This will help ameliorate the water supply challenges facing most rural villages. The dam can also be fenced and livestock water can be provided downstream of the dam wall via an array of drinking troughs that may be constructed for this purpose.
The lake created by the dammed water can be utilised for recreational purposes, whereby a camping site can be established on the banks of the lake and when the water levels are high. By introducing selected fish species into the dam, the local community can benefit not only from an enriched diet of fish protein, but also from limited fish trade amongst local villages.
Sustainability of the Nwamankena Dam Project is hinged on the following four main factors:
- Community participation and their full engagement from the project planning onwards.
- Development of the water resource to bring out high-impact social-economic benefits that the community will have access to, and enjoy these benefits in the short and long term.
- Effective government of the water resource and community-owned catchment management systems.
- Adequate support from key stakeholders such as the Department of Water Affairs; the Department of Environmental Affairs; the Department of Agriculture;the greater Giyani Local Municipality and the Mopani District Municipality.