Blackwater river
This article is about a classification of rivers. For rivers officially named Blackwater
, see Blackwater River.Blackwater rivers are rivers with
waters colored like clear
tea to
coffee. Most major blackwater rivers are in the
Amazon River system and the
Southern United States.
 |
Amazon River tributary classified as blackwater |
A blackwater river is one with a deep, slow-moving channel that flows through
forested
swamps and
wetlands. The term blackwater describes the appearance of the water of such rivers, which is a dark
coffee color. This color results from the leaching of
tannins from the decaying
leaves of adjoining vegetation.
Black and
white waters differ significantly in their ionic composition, as shown in Table 1 below. Black waters have ionic concentrations not much greater than that of
rainwater. They are, however, much more
acidic and this results in black waters having an
aluminium concentration greater than that of the more neutral white waters. The most striking differences are in the concentrations of
sodium,
magnesium,
calcium and
potassium; these are very low in black waters. This has considerable ecological implications. Some animal groups, such as
snails, need a lot of calcium with which to build their shells and so are not abundant in black waters. The lack of dissolved ions in black waters results in a low
conductivity, similar to that of
rainwater.
Black and white waters also differ in their
planktonic fauna and
flora. Tables 2 and 3 below compare the number of planktonic animals caught in black and white water localities only a few meters apart. In fact, the black water was not even as extreme an example as can be found in the
Rio Negro system. However, it can be seen that the black water held far greater numbers of
rotifers but fewer
crustaceans and
mites. These crustaceans are important foods for
larval fish. The zones where the two waters mix are particularly attractive to
ostracods and young fish. Anywhere in the world where you see these mixing zones there tend to be high numbers of animals and this is certainly the case in the
Amazon. The high abundance of animals is shown clearly in Table 3 which compares the numbers of animals present in 10 litres of water in each habitat sampled.
[Comparison between white and black waters. (no date). Retrieved May 21, 2006 from http://www.amazonian-fish.co.uk/indexc30.html ]| Table 1: Mean ionic composition, specific conductivity (μS/cm), and pH in Amazon waters. Data from Ribeiro and Darwich (1993). |
| | Solimoes or Amazon river â€" whitewater. | Rio Negro â€" blackwater. |
| Na (mg/L) | 2.3 ± 0.8 | 0.380 ± 0.124 |
| K (mg/L) | 0.9 ± 0.2 | 0.327 ± 0.107 |
| Mg (mg/L) | 1.1 ± 0.2 | 0.114 ± 0.035 |
| Ca (mg/L) | 7.2 ± 1.6 | 0.212 ± 0.066 |
| Cl (mg/L) | 3.1 ± 2.1 | 1.7 ± 0.7 |
| Si (mg/L) | 4.0 ± 0.9 | 2.0 ± 0.5 |
| Sr (μg/L) | 37.8 ± 8.8 | 3.6 ± 1.0 |
| Ba (μg/L) | 22.7 ± 5.9 | 8.1 ± 2.1 |
| Al (μg/L) | 44 ± 37 | 112 ± 29 |
| Fe (μg/L) | 109 ± 76 | 178 ± 58 |
| Mn (μg/L) | 5.9 ± 5.1 | 9.0 ± 2.4 |
| Cu (μg/L) | 2.4 ± 0.6 | 1.8 ± 0.5 |
| Zn (μg/L) | 3.2 ± 1.5 | 4.1 ± 1.8 |
| Conductivity | 57 ± 8 | 9 ± 2 |
| pH | 6.9 ± 0.4 | 5.1±0.6 |
| Total P (μg/L) | 105 ± 58 | 25 ± 17 |
| Total C (mg/L) | 13.5 ± 3.1 | 10.5 ± 1.3 |
| HCO3-C (mg/L) | 6.7 ± 0.8 | 1.7 ± 0.5 |
Amazonia
*
Apaporis River: A tributary of the
Yapura River.
*
Arapiuns River: A tributary of the
Tapajós River.
*
Coari River*
MiritÃ-Paraná River*
Negro River: By far the largest blackwater river in the world; one of the largest Amazonian tributaries.
*
Piorini River*
Tahuayo River*
Tefé River*
Uatamã River*
Urubu River*
Vaupés*
Atabapo: from the
Guiana Highlands of
Venezuela west into the Orinoco
*
Caronà River: from the
Guiana Highlands of
Venezuela west into the Orinoco
*
InÃrida: from
Colombia northeast into the Orinoco, flows first into the
Guaviare River and this flows into the
Orinoco*
Ventuari: from eastern
Venezuela (the
Guiana Highlands) southwest into the Orinoco
*
Vichada: from
Colombia east into the Orinoco
*
Tomo: from
Colombia east into the Orinoco
*
Tuparro: from
Colombia east into the Orinoco
Southern United States
*
Blackwater River: a tributary of the
Chowan River in
Virginia in the
United States.
*
Black River: a tributary of the
Pee Dee River in
North and
South Carolina in the
United States.
*
Cape Fear River: A large river in
North Carolina in the
United States flowing into the
Atlantic Ocean.
*
Cashie River: A river in
North Carolina in the
United States flowing into
Albemarle Sound.
*
Caloosahatchee River: A river in
Florida flowing west from
Lake Okeechobee to the
Gulf of Mexico.
*
Chowan River: A river in
North Carolina in the
United States flowing into
Albemarle Sound.
*
Edisto River: A river in
South Carolina in the
United States flowing into the
Atlantic Ocean.
*
Great Coharie Creek: A river in
North Carolina in the
United States flowing into the
Black River.
*
Little Pee Dee River: A river in
South Carolina in the
United States flowing into the
Pee Dee River.
*
Lumber/
Drowning Creek: A river in
North and
South Carolina in the
United States.
*
Suwannee River: A large river in southern
Georgia and northern
Florida in the
United States flowing into the
Gulf of Mexico.
*
Upper Little River: A river in
North Carolina in the
United States flowing into the
Cape Fear River.
*
Waccamaw River: A river in
North and
South Carolina in the
United States flowing into the
Atlantic Ocean.
*
White Oak River: A river in
North Carolina in the
United States flowing into the
Atlantic Ocean.
North America
*
Tahquamenon River: A river in the
Upper Peninsula of
Michigan flowing into
Lake Superior.
*
Blackwater River, a list of rivers by this name.
