The largest freshwater lake in China looks like a giant oil spill through the eyes of the European Space Agency's Copernicus Sentinel satellite.

ESA released new radar imagery of Poyang Lake on Friday -- imagery recently captured by Copernicus Sentinel-1 as it passed over Southern China at an altitude of 431 miles.

Poyang Lake is a vital ecological resource. It serves as the wintering grounds for Siberian cranes, or snow cranes, which migrate thousands of miles across Asia.

The Indo-Pacific finless porpoise, Neophocaena phocaenoides, a freshwater mammal noted for its intelligence, also calls Poyang home. The porpoise is highly endangered. At its current rate of population decline, scientists predict the species will be extinct in less than a decade. The Chinese government recently relocated several specimens from the lake for a breeding program.

Poyang is also an important freshwater source for the many rice farms in the region, but seasonal precipitation causes the lake's water levels to fluctuate dramatically. A wetter than usual monsoon season triggered by El Nino only recently raised the lake's water levels after almost a decade of drought conditions.

Chinese scientists have been working with ESA researchers to monitor the lake's water levels as part of the Dragon program. Satellite imagery captured by the Sentinel-1 mission has previously been used in support of the Dragon program.