Scientists are exploring a new nanotechnology based floating cover that could help reduce water loss from lakes, dams and reservoirs by blocking heat from the sun while still allowing enough visible light to reach the water.
The idea described by physicist Daniel Kwasi Kpeglo of the University of South Africa, works like a sunscreen for water. The lightweight floating material is designed to reflect heat carrying infrared radiation while allowing much of the visible sunlight needed by aquatic plants and animals to pass through.
Water evaporation is a major challenge for reservoirs, particularly in hot and dry regions. Rising temperatures are increasing evaporation rates, reducing the amount of stored water available for households, agriculture and industry.
The experimental cover uses a very thin layer of transparent conducting oxide placed on a lightweight and flexible plastic sheet. The material floats directly on the water surface and acts as a selective filter for sunlight.
During laboratory tests, the cover allowed more than 60% of visible light to pass through while reflecting over 80% of infrared radiation. Researchers found that the water beneath the coated cover remained significantly cooler, with temperatures up to 10 degrees Celsius lower during the sunniest part of the day.
The reduction in heat reaching the water helped minimise evaporation. In the laboratory experiment, the water level under the coated material remained almost unchanged during the testing period, while water levels dropped in uncovered containers and those covered with ordinary plastic sheets.
Researchers say the technology could offer advantages over existing methods used to reduce evaporation. Traditional approaches include shade structures, floating covers, wind barriers, plants and natural materials such as palm fronds.
Some proposed chemical solutions can also reduce evaporation but may block sunlight completely. The new nanomaterial design aims to avoid this problem by allowing visible light to pass through while blocking a significant amount of infrared heat.
Another potential advantage is the material’s lightweight design. The nanomaterial coating is only a few hundred nanometres thick and is applied to a flexible plastic sheet, making it easier to handle than large permanent shade structures.
The coated surface is also water repellent and showed less tendency to develop algae and other natural growth during testing, which could potentially reduce cleaning and maintenance requirements.
However, researchers stressed that the technology is still at an early stage. The experiments were carried out only at laboratory scale using an artificial light source designed to mimic sunlight.
Large scale field trials will be needed before the technology can be used on real lakes and reservoirs. Scientists need to determine how the material performs under changing weather conditions, including strong sunlight, wind, rain and fluctuating temperatures.
Questions also remain about the material’s durability, cost and environmental impact. Researchers say future designs may need ultraviolet resistant materials to ensure the floating sheets can withstand years of exposure to sunlight without breaking down.
The technology would also need a secure floating or anchoring system to prevent wind and moving water from shifting the material across large reservoirs.
Despite these challenges the research offers a potential new approach to water conservation. If proven effective at a larger scale a thin floating nanomaterial cover could help communities retain more of the water already stored in dams and reservoirs, reducing pressure on increasingly limited water resources.