Cover supplies water evaporation reduction

Rio Tinto’s Northparkes mine has achieved a 95% reduction in evaporation losses thanks to a new water storage facility cover.

Rio Tinto’s Northparkes mine has achieved a 95% reduction in evaporation losses thanks to a new water storage facility cover.

Nylex and Rio Tinto joined forces to produce a product that efficiently reduced water evaporation from large open water storage facilities.

The Nylex Aquacap can reduce both solar and wind evaporation whilst allowing rain water to enter the water storage, maintain water quality and be easy to assemble and transport.

The product is a 1,150 mm diameter, circular, modular disc made of non-toxic, injection moulded, white polypropylene that floats semi-submerged on the surface of the water.

The surface of each disc is solar reflective and curved to reduce both solar and wind evaporation.

When fully deployed, the circular discs cover up to 80% of the water’s surface, allowing sufficient natural light to penetrate and minimise ecological disruption, prevent the build up of hazardous gases and maintain water quality.

According to the tests conducted by Rio Tinto, a single disc can support a 3kg vertical load. This means that it will not sink if a bird lands on it or if it is covered with snow.

Wind tunnel tests demonstrate that the curved surface of the Nylex Aquacap enables it to resist wind speeds of up to 130kph.

In 2006, trials were carried out at Rio Tinto’s Northparkes Mine, 25Km north of Parkes, NSW.

Average rainfall for the area was 584 mm/y with an annual evaporation of 1570 mm/y.

During the trials, the products were deployed over two purpose built storages, each with a surface area of approximately 0.63ha.

The trails were designed to demonstrate the Nylex Aquacap Modular system’s ability to reduce water loss through evaporation from a working mine. The water levels of both storages were measured using accuracte pressure sensitive transducers.

Seepage was estimated and removed from the water level data for both storages, leaving evaporation as the sole course of changes in water height.

During the trial, the covered storage lost 210 mm in evaporation and the control storage lost 1,445 mm — resulting in a saving of 1,235 mm or an 85% reduction in evaporation losses.

The percentage reduction changed during the year with a maximum reduction of 95% achieved during winter.

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