Algal bloom in an intensively used lake
Background
With the increasing intensity of aquaculture in East Taihu, China, the amount of nutrients in the Lake Taihu has increased. This so-called eutrophication led to an increased algal growth and a decreased water quality. As a consequence, the water supply in surrounding areas suffered. In addition, development of marshiness in the eastern littoral zones and East Taihu has occurred.
From 1993, the entire lake suffered eutrophication, a process in which an excess of nutrients such as nitrates and phosphates causes an algal bloom. The increased growth of algae removes oxygen and reduces the water quality, causing fish and other organisms to die. These algal blooms have become increasingly severe.
In response to these challenges, the Chinese authorities have launched a series of projects to reduce the inflow of nutrients into the lake. While the water quality has improved significantly, algal blooms remain a issue in Lake Taihu. In addition to in-situ measurements, satellite data are a valuable tool for monitoring the state of the lake.
Exercises
- Satellite Map:
- Look at the satellite image maps and deselect all satellite images by unticking the respective boxes.
- Now add the overview satellite image from 2019 to the map.
- Which land cover classes can you identify around the lake?
- Add the detail satellite image from 2019-08-12 and zoom in.
- Add the detail satellite image from 2019-08-17, taken only five days after the first one. Toggle between these two satellite images. Which changes can you identify? Have you found the green algae cover?
- Where can you find an increase of algae in the water?
- Compare this with the satellite image from 2020.
- What are the line-shaped structures in the algae carpet?
- How do the algae affect the people living there?
- EO Browser:
- Open the EO Browser.
- Find the most recent Sentinel-2 dataset covering the area displayed in the satellite map.
- Select a true colour visualisation.
- What can you say about the algae situation in the Lake?
- Select the false colour infrared representation. Can you identify the land-use of the most intensely vegetated areas (represented by bright red colours)?
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