Water basin covers.

Shade-cloth keeps water storages cleaner

Textile covers on four township water supply basins in East Gippsland reduced evaporation, prevented the incidence of algal blooms and kept the water cleaner.

• 22 September 2008 | Updated 14 October 2011

• Algal bloom problems in water basins
• How CSIRO helped
• Six basins studied
• Tough fabric
• No blooms
• About the scientists

Algal bloom problems in water basins

Many townships get their drinking water from specially constructed small water basins that are topped up from local rivers during times of clear water flow.

Algal blooms within the basins are a major problem. Controlling algal growth often requires attention from maintenance staff and additional chemical usage.

How CSIRO helped

As part of a research program on technical textiles, a team from CSIRO monitored water properties in water supply basins covered with heavy duty shade-cloth.

The project was set up after promising results from the covering of a single basin in East Gippsland, Victoria, Australia, in 2001. The covering blocked the light and reduced algal growth, so a more comprehensive trial was set up in 2004.

Its aims are to improve water quality by:

• reducing light levels to minimise algal and plant growth
• reducing entry of wind-borne debris
• keeping birds out, especially water birds
• reduce evaporation
• improve security of supply
• reduce chemical use
• improve security against wilful contamination.

Six basins studied

CSIRO partnered with the manufacturer Gale Pacific and East Gippsland Water on the project, which ran for two years.

Four basins were monitored for one year uncovered and one year covered. Two of these are treated-water storages (Mallacoota and Omeo) and two are raw-water storages (Swifts Creek and Cann River). Two uncovered basins (Sarsfield and Orbost) were monitored for two years.

Observations are in the final stages of analysis.

Tough fabric

Shade-cloth covers were specifically designed by Gale Pacific Limited to block about 95 per cent of the light. They had to be strong, durable, UV stable, abrasion-, flex-, and heat-resistant, and be able to sustain tensions for long periods in extremes of heat, cold, and windy conditions.

The fabrics are knitted from high density polyethylene monofilament yarns and tapes, supported externally by steel cables and poles situated outside the basin banks.

The covers and their support structures were designed, fabricated and installed by Superspan Pty Ltd.

The support structures had to withstand high winds and snow loadings. The covers were tensioned with about 1500 kg force at each mounting point.

No blooms

No significant algal blooms occurred in covered basins during the 2005-06 summer.

The Omeo basin was usable throughout the summer, especially over weekends, significantly reducing the hours required to tend the treatment plant. In previous summers, algal blooms made the basin unusable for periods.

The Omeo cover also withstood high winds and heavy snow falls in 2005.

Adverse bacterial events became rare in the treated-water storages but were much the same in the raw-water storages, which are fed directly from rivers.

Water birds and wind-borne debris were kept out by the covers.

Plants no longer grew at the bottom of the basins because of the lack of light, and this reduced maintenance costs.

About the scientists

The scientists involved included:

• Dr Niall Finn, who researches technical textiles and leads a number of projects at CSIRO
• Mr Scott Barnes from CSIRO Materials Science & Engineering who carried out many of the on-site water quality measurements.

Read the full report on The benefits of shade-cloth covers for potable water storages