Classify Land Cover to Measure Shrinking Lakes



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Environmental Systems Research Institute

Author Esri

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Water Diplomacy
Asia and the Pacific

Lake Poyang, China’s largest freshwater lake, is shrinking as upstream water is pulled from the Yangtze River at the Three Gorges Dam. Those whose livelihoods depend on the lake are alarmed, as the shrinking lake changes the land cover of the area and impacts the economy. To help them make a case to save the lake, you’ll compare imagery between 1984 and 2014 to quantify the surface area of the lake and show changes over time.

To calculate the lake’s change in area over time, you’ll compare imagery of the lake taken by Landsat satellites between 1984 and 2014. The Landsat satellite program has been in operation over 40 years, making its imagery vital for monitoring major planetary changes. You’ll classify the pixel values of the imagery into categories based on land cover. Then, you’ll display only land cover of Lake Poyang, isolating the lake from the rest of the image. Then,¬†you’ll clean up your classified images with generalization analysis tools to remove small errors or minor water bodies around the lake. You’ll also smooth the lake’s boundaries. After preparing your images, you’ll calculate the area of the lake over the past 30 years and determine how much it has changed.

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