Hexagon WEPLarge parts of South Africa are currently in the grip of a crippling drought. Much of the affected areas will not be able to recover in the medium term, even with sustained and substantial rainfall.

A key contributor to water stress is evaporation. With South Africa’s long sunshine days, dry climate and shallow storage dams, evaporation rates are in the extreme.

New design and technology developed now may contribute to reducing evaporation rates.

Technology Options Ensure Stability in RSA Water Conservation and Water Use

Given the perpetual water shortages in the Western Cape, The Southern Cape Landowners Initiative (SCLI), has invested in the research and development of water evaporation prevention (WEP) solutions.

On average, evaporation rates in RSA are in the region of 2000 mm per annum. This figure, converted into a percentage figure, means that many storage dams can lose over 60% of their capacity over a twelve month period.

Storage dams in the Western Cape lose an estimated 2% of their capacity every week. The accumulated percentage of water lost to evaporation is staggering.

Damage to ecological systems, natural infrastructure and aquatic life, exponentially reflects the damage done through the evaporation of stored waters.

Worldwide, technology options to protect stored waters from evaporation, are limited, and generally too expensive for water users to implement as a water conservation option.

RSA can benefit from implementing water evaporation prevention (WEP) systems on stored waters

Best practice and water stewardship models in South Africa are resulting in increasingly responsible water users.

However, climate change, reduced rainfall, aging infrastructures, episodic rainfall, and concentrated (urbanized) development, makes water security problematic in the short, medium and long term.

Given the projected water use, and water stress scenario of RSA, the country has little option other than to turn to technology, in order to create a secure and stable water use environment.

RSA water evaporation prevention technology piloted for viability and durability

Rooted in the demands of the water dependent mining and agriculture sector, technology options to protect stored waters from evaporation has been in the making by SCLI for some time.

Although all the technology options developed over the past few years were all successful in suppressing evaporation rates, not all were able to successfully survive severe natural conditions.

Critical factors, such as exposure to very strong wind, wave action and harsh sunlight, are but some of the requirements that designs and material had to be able to withstand.

Another critical factor was the related manufacturing and installation costs.

Through a process of elimination, SCLI has now designed, built and installed a floating evaporation cover for open water bodies.

Hexagon WEP

Materials Used

  • Non bio-degradable air wrap
  • Built-in UV Protected
  • Certified non-toxic pigment colouring

Effectiveness in evaporation suppression

  • Effectiveness in reducing evaporation rates correlates to the surface area covered.
  • In order to allow for rain and splash-over water run-off, spaces must be allowed between cover sheets, and a small percentage of evaporation will take place.

Life Expectancy

Seven to ten years, dependent on maintenance levels and water quality

Impact of WEP Systems in Ecological System Drivers and Aquatic Life

Ecological system drivers, such as sunlight penetration (euphotic zone), as well as maintaining sufficient levels of oxygen concentration, are vital considerations in applying WEP systems.

The WEP material used is pigmented to ensure (some) shade to cool the water column, but to allow sunlight penetration.

By spacing out WEP covers to allow for splash over and maintenance channels, sufficient levels of oxygen is maintained to support aquatic life.

Associated Costs

There are several variables influencing costs, however estimated production cost is approximately R125 per m2 – (Terms & Conditions Apply).
Cost excludes delivery and installation – to be calculated separately.

The Southern Cape Landowners Initiative (SCLI), is a public platform for landowners and land managers with an interest in the control and eradication of Invasive Alien Plants SCLI is supported by the Table Mountain Fund (TMF).

Written by Cobus Meiring