**Calculating Water Evaporation – Estimated reduction in evaporation (percentage)**

Determining exact evaporation figures is not a simple calculation, as there are many contributing factors to consider, such as ground seepage, etc. However, for the purpose of this exercise, calculations will be based on 20%.

In a dam with a surface area of 10 hectares, containing 1 million cubic litres of water, the evaporation figure would be around 200 000 cubic litres per annum.

In theory, covering 10% of the surface area should bring about a reduction of surface water evaporation of approximately 8% (evaporation figures will not exactly reflect the area covered).

Amount of water saved per annum: 80 000 cubic litres of fresh water.

The total surface area covered with Hexagon-WEP® would ensure a reduction in relation to (surface) size covered, less the area exposed.

The evaporation reduction will not necessarily equate to exactly the area which is covered, as there will still be a percentage of water loss.

Consideration must to be given to unforeseen water loss factors, such as dam wall leakage and other variables such as areas in South Africa, that are exposed to consistently strong prevailing wind, which will reflect a more noticeable reduction in evaporation.

### PREVENTION OF DAM WALL EROSION AND DAM SILTATION

#### For further assistance please contact

Cobus Meiring from SCLI at cobus@naturalbridge.co.za