Lakes in cities have many issues confronting their survival. One of them is the nutrient-rich environment that they occupy. Waste-water from sewage which enters these water bodies are naturally nutrient rich but also stormwater. Nitrates and phosphates are ubiquitous in the urban environment. Once they enter the lakes they cause algal blooms and the growth of macrophytes such as water hyacinths.
The idea of floating islands has been tried in the lakes of Indore. Puttenahalli in South Bengaluru and Jakkur and Rachenahalli in North Bengaluru have used floating wetland islands to treat the nutrient-rich water too. In a recent visit to the Royal Botanical Park in Melbourne one saw floating islands being used to clean storm-water. There has been a significant reduction in algal blooms in the waters of the lakes here.
A variety of plants can be used for these floating islands. They all look lovely and green with flowers. They provide a habitat for birds and insects. The long roots below allow for absorption of nutrients from the lake waters.
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The floating islands can be towed in and harvested regularly to allow for new growth for it is at the growth stage that plants absorb the maximum nutrients.
By fringing our lakes with floating islands not only can the lake waters be remedied but also the steep edges can be modified to provide a habitat for many birds. Fish too love the root zone of these islands.
Using bamboo and coir, even the base of the floating islands can be made eco-friendly. Trying out floating islands in our lakes would be water wisdom.
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