bin
Rio Negro Basin, Brazil
Brazil, Amazonas
The Rio Negro is the largest blackwater tributary of the Amazon River. As the name suggests, the Rio Negro means “black river” although it is not as black as imagined and even looks like strong tea. The black color comes from organic acids that are not completely broken down by the vegetation around the river.
In Colombia, the Rio Negro River is also known as the Río Guainía, the river flows into the Amazon River in region of Manaus.
- Submitted by
- Mohammad Arief Rachman Hakim
- Approved by
- Roberto E. Reis & Pablo C. Lehmann
- Geographical region
- South America
- Drainage Basin
- Rio Amazonas
- River catchment
- Rio Negro
- Water body type
- Igarapè
- Water body name
- Nameless affluent
- Water body part
- Marsh land
- Water body course
- Lower course
- Water body: tributary of
- Rio
- Tributary name
- Rio Negro
Warning: Undefined variable $fish_parent in /home/biotopea/public_html/wp-content/themes/bap/content-bin.php on line 55
Water Chemistry
Water information
- Water type
- fresh-water
- Water color
- Black water
- Water transparency
- Medium
- Concentration of sediments
- Medium
- Water temperature
- 29-30 °C
- Water flow/curent
- Slow
Chemical parameters
- pH
- Conductivity
- 8
- GH
- dGH
- KH
- dKH
- Dissolved Oxygen
Substrate in nature
- Sand
- White
- Pebble/Gravel
- Orange
- Stone
- Brown
- Stone form
- Irregular
- Silt/Mud
- None
- Leaves
- Many
- Driftwood
- Many
- Submerged terrestrial vegetation
- Yes
Aquatic Biotope
- Date of collecting
- 15 February, 2024
- Collecting area
- Flooded area
- Water depth
- 1,0m
- Air temperature
- Sunlight
- Filtered/dappled sun
Environment
- Environment
- Affected by human activity
- Affected by human activity
- Deforestation
- Agriculture
- Advanced
- Deforestation
- Initial
- Surrounding area
This ecoregion includes the Rio Negro drainage basin from Manaus in the east to the slopes of the eastern cordillera of the Andes in Colombia. It includes the lower Rio Branco downstream from Caracaraí and the lower Rio Jauaperi basin. It is bounded in the north by the mountainous divide between the Negro and the Orinoco and upper Rio Branco drainage. The southern limit is formed by the low-lying divide between the Rio Negro tributaries and the Rio Solimões drainage.
- Underwater landscape
Low gradient rivers and streams run through sedimentary soils formed mainly by podsols subjected to seasonal flooding. The Rio Negro’s water is extremely poor in mineral content, with conductivity as low as 8µS, and is extremely acidic, with pH ranging 2.9-4.2.
The largest blackwater river in the world, the Rio Negro provides roughly 14% of the average annual discharge into the Amazon, second only to the Madeira. Its main tributary, the Rio Branco, is by contrast a whitewater river. Although not as turbid and the Amazon or Madeira, it is muddy during the flood season. The sediments are visible 200km downstream of the confluence with the Negro.
The headwaters of the Negro originate in the foothills of the Andes. In the upper reaches the flood season occurs between May and September, peaking in July. Water level fluctuations in the lower reaches are dictated more by the Amazon, and occur earlier.
Here, the flood season lasts from February through July, with peak water levels in June. The average annual river fluctuations range between 4-5m in the upper reaches and 10m in the lower reaches. It is estimated that an area of 30.000km² within the Negro basin is seasonally flooded between 4-8 months of the year. The largest floodplains occur along right-bank tributaries, as well as among the network of islands along the middle and lower Rio Negro.
There are many insular environments along the main stem of the Rio Negro, including more than 600 islands in the lower and mid-section of the river. Along the main stem and tributaries are vast fringing floodplains covered by flooded forests and inundated campinas and caatingas (campinarana), as well as many floodplain lakes and oxbow lakes along the channels. During the dry season vast sand beaches are found along the entire extent of the rivers. River bottoms are rocky with gravel and large boulders. Rocky outcrops and cataracts reveal evidence of the Guiana shield at points along the Rio Negro’s middle reaches.
- Threats to ecology
Ecological phenomena include large migrations of doradid catfishes, characids such as Brycon, and Prochilodontids of the genus Semaprochilodus. The jaraqui (Semaprochilodus insignis), for example, migrates from blackwater to whitewater rivers to spawn. There are also unique assemblages of species on leave-litter deposits, and many miniaturized forms.
Riparian zone
- Trees near the aquatic habitat
-
Many -
