Flooding favors river concluence in the Pantanal

The large volume of rainfall hitting the southern Pantanal in Mato Grosso do Sul this year is enabling a phenomenon not always seen: the meeting of rivers with different colors.

In the Nhecolândia region of the Pantanal, the Negro and Aquidauana rivers split the water landscape into two tones — one lighter and the other darker.

The two rivers were once connected in the past.

But due to the Pantanal’s unique geography, which allows river courses to shift, they only reconnect during flood seasons.

According to Edna Facincani, a specialist professor at UFMS (Federal University of Mato Grosso do Sul), this occurs because the Pantanal basin lies in a subsidence region, where the ground sinks in the underground layers.

As a result, during heavy rains, the old channel that once linked the Aquidauana and Negro rivers is reactivated. This creates a large lake and leads to the color-blending phenomenon that reflects the beauty of the Pantanal.

Among the reasons for this occurrence are the physical and chemical conditions of the rivers.

Factors such as water temperature and pH, flow speed, and volume all contribute to the mixing process.

The composition of the soil and the difference in sediment levels in each river also play a role. The Negro River carries fewer sediments, resulting in clearer water.

The phenomenon is expected to last until the end of the flood season.

Historically, without the influence of climate change, this period runs from October to May.