‘Blanket’ keeps lid on open-stored water

from The Farmlander - October 2021 South

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While many parts of New Zealand seem to be experiencing flooding and above-average rainfall, in only a few months this could change to long dry spells.

Available information about the effects of climate change to our seasons has made water management and planning somewhat of a lottery. With good foresight there is still a lot that can be done to mitigate the effects of available open-water storage for both stock and irrigation. The effects of evaporation on openwater storage reserves are immense and often underestimated. A single square metre of water surface can easily lose up to 8 litres to evaporation every day in summer, and a 1ha dam can lose up to 80,000 litres of water that is essential for animals and growing crops. These water loss figures have been largely meaningless to the industry to date, with limited management options available to reduce the water loss. It has become accepted that a large percentage of open-stored water will be lost to evaporation. This is not too significant if the volume of fill is greater than the net loss through usage or evaporation. Once a dry spell sets in this can change very rapidly and the net loss then becomes hugely significant. You can now reduce the effects of evaporation on a surface area of any size. New product WaterGuard can be simply poured on to any water surface, usually by just walking along a length of the dam while pouring. A product that is safe on crops and stock and reduces evaporation by up to 60 percent has the potential to be a game changer. It does not need to be applied around the full perimeter. For very small dams, it can be applied at a single point. For large reservoirs or dams WaterGuard can be applied from several points along the edge of the water storage or even by air or boat. As with smaller water bodies, it should be applied from locations along the edge such that the prevailing wind will assist it to spread. WaterGuard is produced from polymers that strongly repel each other when they come in contact with water. This results in a strong spreading action across the surface, forming a liquid ‘blanket’ to reduce evaporation. Once the film is in place, it is very resistant to disturbances. It will move around slowly over the surface but will not build up at one end of the water body. In the event of rain, the blanket will not be affected as it will allow the rain to go through without disturbing the film.