the theme in 2018 explored how nature can be used to overcome the water challenges of the 21st century. this could be in the form of nature-based solutions to water-related challenges. for example, reducing floods, droughts, water pollution and protecting ecosystems could be solved using natural means, which nature uses, rather than man-made approaches. restoring wetlands, implementing constructed wetlands, green roofs, green infrastructure, planting new forests, reconnecting rivers to floodplains, are some examples. each of these use natural processes to rebalance the water cycle and improve human health and livelihoods.