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Clanwilliam Dam Bulk Conveyance Infrastructure

Background Information

The existing Clanwilliam Dam is small relative to the annual runoff from the catchment area and the scheduled allocations, and existing irrigators are restricted every year. The feasibility study for the raising of Clanwilliam Dam recommended that the existing dam be raised by 13 m, and that further agricultural development is economically viable and socially desirable. Construction to raise the dam wall has started in 2018 following significant delays. The planned raising of the Clanwilliam Dam wall by the Department of Water and Sanitation is regarded as a major step forward in addressing water allocation reform in the lower Olifants River area.

Incremental Yield

The resultant increase in the capacity of the dam from 122 million m3 to 344 million m3 will provide 82.1 million m3/a additional water for irrigation and for other future water uses. The additional water will firstly be used to maintain the status quo of the ecological water requirements of the Olifants River below the dam. Some of the additional water will be used to improve the level of assurance of supply for irrigation water to existing irrigators to a level consistent with water allocation policy. The bulk of the additional water will provide irrigation water to emerging farmers in identified areas, where new agricultural development will be economically viable and socially desirable.

Post Feasibility Bridging Study

The Post Feasibility Bridging Study for the Proposed Bulk Conveyance Infrastructure from the Raised Clanwilliam Dam was concluded in June 2021, to obtain recommendations on the bulk conveyance infrastructure required for the equitable distribution of water from the existing dam, as well as the additional water, which will be available from the raised Clanwilliam Dam. This was determined after an investigation into the existing and potential future water use and allocations for the supply area, potential new areas for agricultural development, options for new irrigation and required conveyance infrastructure, appropriate farming models and the expected cost of bulk irrigation infrastructure. Zutari (Pty) Ltd was appointed to conduct this study. Information of existing water allocations from the Clanwilliam Dam, the current extent of water use, and the status and extent of existing bulk conveyance infrastructure have been confirmed, as well as the additional amount of water (yield at various assurances of supply) available from the raised dam. A soil survey has been conducted to extend the 2012 soil survey undertaken of soil suitability in the Olifants River valley. An assessment was done to provide an overview of the extent and general condition of the current bulk water infrastructure. The financial viability of farming in different sub-regions, for pre-identified crop-mixes was investigated, to form an opinion on the desirability of and preferred type of farming in these sub-regions, for different farming models, to advise on agricultural business models, financial viability and cash flows. Options analysis entailed the identification and assessment of alternative approaches to supplying and storing water for new irrigation development options, either expanding existing farms, more intensive farming or greenfield development. Environmental screening of the early proposed development areas and activities was conducted, to determine the best ecological options and to minimise impacts on the natural environment. More detailed environmental assessments were later undertaken, in support of the feasibility designs. Salient features of potential irrigation schemes were identified, and costs were established. A screening process was followed to identify the preferred options to evaluate further at feasibility level. Five recommended irrigation schemes are located upstream of Bulshoek Weir and five schemes downstream, both for the development of new land as well as the replacement of lower-value crops with higher-value crops. A total of 5 874 ha is recommended for new irrigation development in a phased approach. Of these schemes, the Jan Dissels Scheme, Right Bank Canal Scheme and Ebenhaeser Scheme were selected for feasibility-level design as Government Waterworks. The remainder of the new irrigation development will be located on privately-owned land. Various “best approaches” have been recommended for the uptake of water on private land, including strategic partnership / mentorship agreements. It is recommended that a balance be found between the development of commercial partnership projects and the development of smallholder plots. Topographical surveys and geotechnical investigations were done in support of the feasibility design and a regional and a national socio-economic impact assessment was carried out. The project stipulates that water should be allocated to historically disadvantaged farmers. Feasibility design of the bulk conveyance infrastructure for the Government Waterworks was done and scheme costs were determined.

Implementation Arrangements

Where bulk infrastructure will be located on or cross privately-owned farms, land and servitudes will need to be acquired from these landowners. Engagement with the Western Cape Department of Transport and Public Works and Transnet Freight Rail will be needed for road and rail crossings. The Department of Forestry, Fisheries and the Environment will be responsible for environmental approval of the three Government Water Schemes. For developments on private land, the Provincial Department of Environmental Affairs and Development Planning will be responsible for environmental approvals. Detailed design for each scheme will commence once the EIA for that scheme has been concluded, and an Environmental Authorisation has been issued. Further investigations for detailed design should be undertaken, inclusive of topographical surveys, geotechnical investigations, construction materials, electrical power supply, and road and railway crossings. Project implementation can proceed as soon as the detailed design and tender documentation are ready, environmental authorisation has been received, and funding from National Treasury has been secured. The Right Bank Canal Scheme and the Ebenhaeser Scheme will form part of the LORGWS. It is expected that all three schemes will be implemented as Government Waterworks and funded by National Treasury. The implementation of the Jan Dissels and Ebenhaeser schemes is dependent on when additional water will be available after the Clanwilliam Dam has been raised. The Right Bank Canal Scheme is a Betterment Works and can be implemented as soon as Environmental Authorisation has been issued and funding made available.

Reports

The following reports have been produced: