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Water retreatment at catchment area


Publication: Mining Weekly
Journalist: Loni Prinsloo

The world’s fifth-largest gold-miner, Harmony Gold, is working with the Department of Water Affairs and Forestry (Dwaf) and the Department of Agriculture at the Sandvet catchment area in the Free State, to manage water resources in the area.

The area has between 400 km to 500 km of canals, which form part of the Sandvet water scheme. The canals roughly stretch from the Erfenis dam to Klipput.

The purpose of the waterways, or canals, is to drain excess water and to lead it to storage areas, where it can be reused by the mine and the local community. The waterways were all constructed using road graders and have a breadth of between 15 m and 20 m.

Harmony Gold states in its Sustainable Development Report that the company makes extensive use of water, and that generally its operations are based in areas where water is a scarce resource, like the Sandvet area. This is one of the main reasons why the company has embarked on a groupwide campaign to reuse process water and increase the efficiency of its water retreatment schemes.

An irrigation system, named the Delivery on Request system, has been implemented at the Sandvet catchment area and is used by the company in conjunction with Dwaf, the Department of Agriculture and local farmers to facilitate the efficient management of water resources and to assist Harmony in its aim of efficient water retreatment.

The Department of Agriculture states that this system is more organised and more conservation orientated than other water conservation systems and is used at other large irrigation schemes in South Africa, including the Loskop irrigation board, the Pongola irrigation board, the Riet river irrigation scheme, the Mooi river irrigation scheme, the Hartbeestpoort irrigation scheme, the Groot Marico irrigation scheme and the Vaalharts irrigation scheme.

With this system, irrigators in the Sandvet area cannot abstract water that they need at will. Each irrigator must submit a written request to Dwaf on a regular basis. The capacity of the canals is not adequate to transport enough water for all the irrigators to abstract water simultaneously.

Further, it takes several hours for water released at the source to reach the users and, therefore, the management of the scheme has to evaluate all requests, calculate the quantity of the release and determine the dates, times and volumes of the release to each irrigator.

The process to manage the system starts with the receipt of a written request for water from each irrigator. These requests are normally done on a weekly basis. The irrigators complete application forms and deposit these forms in a special box.

The scheme is normally divided into sections and the water control official of each section empties these boxes at a predetermined time. By using the requests, the water control official compiles a feeder chart, which is a summary of the requests in a specific section, and a commission for each canal guard, which stipulates when each sluice should be opened and for how long. The sluices are normally set for a predetermined flow rate regulated by a constant upstream water depth created by a long weir in the canal.

Each canal’s losses are calculated and added to the requested volume of water in order to determine the requested inflow into the specific canal.

The requests from all the different canals are summarised and losses in the main canal are added to determine the total amount of water that must be released at the source. At the end of a period, a disposal report is produced to summarise all the requests and deliveries.

These disposal reports summarise all the information as time goes by, until a final report at the end of each water year displays the results of the past year, and determines the effectiveness of the Sandvet water scheme.

Annual report

Integrated annual report 2016
Integrated annual report 2016

(HTML & PDFs)

Investor brief

Harmony Investor brief, Sep 2017
September 2017 -
Harmony Investor brief

(PDF - 6.5MB)

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