Blackwater river

A blackwater river is a type of river with a slow-moving channel flowing through forested swamps or wetlands. As vegetation decays, tannins leach into the water, making a transparent, acidic water that is darkly stained, resembling tea. Most major blackwater rivers are in the Amazon Basin and the Southern United States. The term is used in fluvial studies, geology, geography, ecology, and biology. Not all dark rivers are blackwater in that technical sense. Some rivers in temperate regions, which drain or flow through areas of dark black loam, are simply black due to the color of the soil; these rivers are black mud rivers. There are also black mud estuaries.

Blackwater rivers are lower in nutrients than whitewater rivers and have ionic concentrations higher than rainwater.[1][2] The unique conditions lead to flora and fauna that differ from both whitewater and clearwater rivers.[3] The classification of Amazonian rivers into black, clear, and whitewater was first proposed by Alfred Russel Wallace in 1853 based on water colour, but the types were more clearly defined by chemistry and physics by Harald Sioli (de) from the 1950s to the 1980s.[3][4] Although many Amazonian rivers fall clearly into one of these categories, others show a mix of characteristics and may vary depending on season and flood levels.[5]

A swamp-fed stream in northern Florida, showing tannin-stained undisturbed blackwater

Comparison between white and black waters

Table 1: Mean ionic composition, specific conductivity (μS/cm), and pH in Amazon waters.[6]
Solimões or
Amazon River
– whitewater
Rio Negro
– 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

Black and white waters differ significantly in their ionic composition, as shown in Table 1. Black waters are more acidic, resulting in an aluminum concentration greater than that of the more neutral white waters. The major difference is the concentrations of sodium, magnesium, calcium and potassium; these are very low in black waters. This has ecological implications. Some animals need more calcium than is available in blackwaters, so for example, snails, which need much calcium to build shells, are not abundant in blackwaters. The lack of dissolved ions in black waters results in a low conductivity, similar to that of rainwater.

Black and white waters differ in their planktonic fauna and flora. Tables 2 and 3 compare the number of planktonic animals caught in black and white water localities only a few meters apart. The black water was not as extreme an example as the Rio Negro system. However, it can be seen that the black water held 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 attractive to ostracods and young fish. These mixing zones tend to have many animals. The abundance is shown in Table 3, which compares animals in 10 litres (2.2 imp gal; 2.6 US gal) of water.[7]

Table 2: Planktonic organisms collected in black (Japura) and white (Solimões) waters.[6]
Animal groups
Rotifera 284 23 0
Cladocera 5 29 43
Ostracoda 39 97 29
Calanoida 11 51 66
Cyclopoida 22 49 61
Chironomidae 0 3 3
Acari (mites) 0 0 2
Table 3: Number of planktonic organisms collected in 10 L of black, white and mixed waters.[6]
Black water Mixed water White water
Animal groups
Forest Open
Forest Open
Volvocaceae 42   38      
Rotifera 87 5 34      
Cladocera 6   5   8 1
Ostracoda 2 11 3   7  
Calanoida 23 3 10      
Cyclopoida 5 27 19 1 13 1
Mysidacea   1        
Diptera         1  
Acari (mites)     1   1  
Larval fish     1   1  

Comparison between clear and black waters

Blackwater rivers resemble clearwater rivers in having a low conductivity and relatively low levels of dissolved solids, but clearwater rivers have water that often only is somewhat acidic (typical pH ~6.5)[3] and very clear with a greenish color.[8] The main Amazonian clearwater rivers have their source in the Brazilian Plateau (such as Tapajós, Tocantins, Xingu and some right tributaries of the Madeira), but some originate in the Guiana Shield (such as Nhamundá, Paru and Araguari).[9]

Blackwater rivers of the world


Orinoco basin

Southern United States

The Lumber River as seen from the boat launch at Princess Ann near Orrum, North Carolina.

Northern United States

Chocolate-colored Tahquamenon Falls



Other rivers in Australia may experience infrequent 'blackwater events' associated with flood waters connecting to forested floodplains and these events may be associated with hypoxic waters. Examples include the Murray River, Edward River, Wakool River and Murrumbidgee River.[14]


Images of blackwater rivers

Amazon blackwater

Amazon River tributary classified as blackwater

Bald Cypress

Cluster of bald cypress trees seen in Trap Pond State Park in Southern Delaware


Manaus, the largest city on the Amazon River, from a NASA satellite image, surrounded by the muddy Amazon River and the blackwater Rio Negro

See also


  1. ^ Janzen, D H (July 1974). "Tropical Blackwater Rivers, Animals, and Mast Fruiting by the Dipterocarpaceae". Biotropica. 6 (2): 69–103. doi:10.2307/2989823. JSTOR 2989823.
  2. ^ Sioli, Harald (1975). "Tropical rivers as expressions of their terrestrial environments". Tropical Ecological Systems/Trends in Terrestrial and Aquatic Research. New York City: Springer-Verlag: 275–288.
  3. ^ a b c Duncan, W.P.; and Fernandes, M.N. (2010). Physicochemical characterization of the white, black, and clearwater rivers of the Amazon Basin and its implications on the distribution of freshwater stingrays (Chondrichthyes, Potamotrygonidae). PanamJAS 5(3): 454–464.
  4. ^ Sioli, H., ed. (1984). The Amazon: Limnology and landscape ecology of a mighty tropical river and its basin. ISBN 978-94-009-6544-7.
  5. ^ Goulding, M.; M.L. Carvalho (1982). "Life history and management of the tambaqui (Colossoma macropomum, Characidae): an important Amazonian food fish". Revista Brasileira de Zoologia. 1 (2). doi:10.1590/S0101-81751982000200001.
  6. ^ a b c J S B, Ribeiro; A J Darwich (1993). "Phytoplanktonic primary production of a fluvial island lake in the Central Amazon (Lago do Rei, Ilha do Careiro)". Amazoniana. Kiel. 12 (3–4): 365–383.
  7. ^ "Comparison between white and black waters". Amazonian Fishes and their Habitats. Pisces Conservation Ltd. Archived from the original on 2011-07-16. Retrieved 2006-05-21.
  8. ^ Giovanetti, T.A.; and Vriends, M.M. (1991). Discus Fish, p. 15. Barron's Educational Serie. ISBN 0-8120-4669-2
  9. ^ Junk, W.J.; Piedade, M.T.F.; Schöngart, J.; Cohn-Haft, M.; Adeney, J.M.; and Wittmann, F.A. (2011). Classification of Major Naturally-Occurring Amazonian Lowland Wetlands. Wetlands 31: 623–640.
  10. ^ Brummett, R.; M. Stiassny; and I. Harrison (2011). "Background". In Allen, D.J.; E.G.E. Brooks; and W.R.T. Darwall (eds.). The Status and Distribution of Freshwater Biodiversity in Central Africa. Gland, IUCN. pp. 1–20. ISBN 978-2-8317-1326-7.CS1 maint: Uses authors parameter (link) CS1 maint: Uses editors parameter (link)
  11. ^ Schliewen, U.K.; and M.L.J. Stiassny (2006). "A new species of Nanochromis (Teleostei: Cichlidae) from Lake Mai Ndombe, central Congo Basin, Democratic Republic of Congo". Zootaxa. 1169: 33–46.CS1 maint: Uses authors parameter (link)
  12. ^ Thieme, M.L.; R. Abell; N. Burgess; B. Lehner; E. Dinerstein; D. Olson (2005). Freshwater Ecoregions of Africa and Madagascar: A Conservation Assessment. Island Press. pp. 60–62. ISBN 1-55963-365-4.
  13. ^ "Noosa River Elanda Point to Campsite Fifteen Canoe Guidebook".
  14. ^ "Archived copy". Archived from the original on 2014-08-08. Retrieved 2014-08-08.CS1 maint: Archived copy as title (link)
Blackwater River (Contoocook River tributary)

The Blackwater River is a 37.5-mile-long (60.4 km) river located in central New Hampshire in the United States. It is a tributary of the Contoocook River, part of the Merrimack River watershed.

The Blackwater River is formed at Cilleyville, a village in the western part of the town of Andover, by the junction of two branch streams that lack official names on current maps. The western branch begins at the outlet of Pleasant Lake in New London and flows east through Chase and Tannery ponds in Wilmot Flat. The northern stream branch begins at the outlet of Eagle Pond in Wilmot and flows south past West Andover and through Bog Pond, joining the outlet of Pleasant Lake just south of the outlet of Bog Pond. Kimpton Brook (formerly known as Quickwater Brook), flowing easterly through the village of Wilmot Center, is the primary tributary of Eagle Pond.

From its start at Cilleyville, the Blackwater River flows east through the town of Andover, passing the village of Potter Place. Beyond Andover village, the river continues to wind its way east, eventually turning south near the Blackwater Bays and dropping over rapids through the village of West Salisbury to the impoundment area of the Blackwater Dam in the town of Webster. Below the reservoir dam, the Blackwater encounters a short, intense whitewater stretch before flattening again for the final miles to the Contoocook in Hopkinton.

Blackwater River (Florida)

The Blackwater River of Florida is a 56.6-mile-long (91.1 km) river rising in southern Alabama and flowing through the Florida Panhandle to the Gulf of Mexico. The river enters Florida in Okaloosa County and flows through Santa Rosa County to Blackwater Bay, an arm of Pensacola Bay. The river passes through Blackwater River State Forest and Blackwater River State Park. Milton, the county seat of Santa Rosa County, is located on the river.

The Blackwater's sandy bottom, white beaches and large sandbars contrast with the dark tannic water that gives the river its name. "Blackwater" is a translation of the Choctaw word oka-lusa, which means "water black".

31 miles (50 km) of the river are navigable by canoe, kayak or small boats. This section of the river, from Kennedy Bridge near Munson, Florida to Deaton Bridge in the Blackwater River State Park, is designated a Florida Canoe Trail — part of a statewide system of greenways and trails.

The river's average flow rate is 2 to 3 miles per hour (3.2 to 4.8 km/h), with an average depth of 2.5 feet (0.76 m). Depending on rainfall, water levels can fluctuate rapidly and low-lying areas are seasonally flooded by the river. This floodplain supports a wide variety of flora and fauna.

Aquatic plants include water fern, water lily, coontail, bladderwort and spatterdock. Oak, maple, sycamore, magnolia, holly, tupelo, mountain laurel and azaleas dominate the forest along the river and streams of the floodplain. Carnivorous plants such as parrot pitcher plants, white-top pitcher plants and sundews can also be found. Upland pine forests are mixed with turkey oak, sweetgum, flowering dogwood and persimmon. Open canopy forests combine several types of pine and dense groundcovers that include gallberry, saw palmetto, wild blueberry, wax myrtle and wiregrass. Atlantic white cedars line the river, and one of these was designated a Florida Champion in 1982, the largest of its species.

Wildlife found nearby include white-tailed deer, turkeys and bobcats. River otters are occasionally seen and alligators are seen frequently. A variety of birds, including red-headed and pileated woodpeckers, hawks, crows, warblers and Mississippi kites frequent the river area. Shorebirds such as plovers and sandpipers, as well as many types of heron and egret, can be found along the banks and sandbars.

The river has spawned many oxbow lakes, some of which can be seen from the river.

Two hurricanes in 1995, Erin and Opal, changed the course of the river downstream from Deaton Bridge in Blackwater River State Park. The section of the river between Deaton Bridge and Milton, Florida is no longer navigable by boat.

The navigable section of the river begins at Kennedy Bridge on State Forestry Road 24 (Kennedy Bridge Road) east of Munson, Florida. The next access point is 6 miles downstream at Peaden Bridge on State Forestry Road 50 (Peaden Bridge Road). Five more miles downstream, between Munson and Baker, Florida, is Cotton Bridge on State Road 4. Twelve more miles downstream is Bryant Bridge, on State Forestry Road 21 (Bryant Bridge Road) near Holt, Florida. The final access point, and the end of the Florida Canoe Trail, is eight more miles downstream at Deaton Bridge on State Forestry Road 23 in Blackwater River State Park.

Blackwater River (Maine)

The Blackwater River is a 7.1-mile-long (11.4 km) river in Aroostook County, Maine. From the confluence of its North Branch and South Branch (46°29′14″N 68°15′07″W) in Squa Pan Township (Township 10, Range 4, WELS), the river runs west to St. Croix Stream in Masardis. Via St. Croix Stream and the Aroostook River, the Blackwater River is part of the Saint John River watershed.

Blackwater River (Maryland)

The Blackwater River is a 25.8-mile-long (41.5 km) saltwater river in Dorchester County, Maryland. It has many twists and bends and flows through Blackwater National Wildlife Refuge. It runs through Robbins, where there is a boat ramp called Shorter's Wharf and a bridge.

The river does not rise anywhere because the water is sea level from its mouth at Fishing Bay to its landward end at a large unnamed swamp in the Blackwater Refuge. The river can have freshwater species in spring and summer like catfish or bass. The river also has saltwater perch and other saltwater fish that prefer upper parts of rivers. In the winter the river is used for waterfowl hunting.

Blackwater River (Massachusetts–New Hampshire)

The Blackwater River is a 3.1-mile-long (5.0 km) tidal inlet in northeastern Massachusetts and southeastern New Hampshire in the United States.The river forms in a salt marsh in the northeastern corner of Salisbury, Massachusetts, by the convergence of the Little River and Dead Creek. Heading north, the river quickly enters Seabrook, New Hampshire and continues to flow through salt marsh until it reaches Hampton Harbor, northwest of Seabrook Beach, where it joins the Hampton River.

Blackwater River (Virginia)

The Blackwater River of southeastern Virginia flows from its source near the city of Petersburg, Virginia for about 105 miles (170 km) through the Inner Coastal Plain region of Virginia (part of the Atlantic Coastal Plain). The Blackwater joins the Nottoway River to form the Chowan River, which empties into Albemarle Sound. The Blackwater-Nottoway confluence forms the boundary between Virginia and North Carolina.

Blackwater River (West Virginia)

The Blackwater River is a 34.3-mile-long (55.2 km) river in the Allegheny Mountains of eastern West Virginia, USA. Via the Black Fork, it is a principal tributary of the Cheat River. Via the Cheat, the Monongahela and the Ohio rivers, it is part of the watershed of the Mississippi River and drains an area of 142 square miles (370 km2). It is a true blackwater stream, owing to spruce and hemlock trees in its watershed, the tannins of which impart a tea or amber color to its water.

Blackwater River Correctional Facility

The Blackwater River Correctional Facility is a private state prison for men located in Milton, Santa Rosa County, Florida, which was opened in 2010 by the GEO Group under contract with the Florida Department of Corrections. This facility houses about 2000 inmates at a variety of security levels.

Blackwater River State Forest

The Blackwater River State Forest is in the U.S. state of Florida. It is located in the panhandle, northeast of Pensacola and at 206,900 acres (849 km²) it is the largest forest in the state.

Blackwater River State Park

Blackwater River State Park is a Florida State Park located fifteen miles northeast of Milton, near Harold, off U.S. 90. The address is 7720 Deaton Bridge Road.

Florida state forests

Florida's state forests are state forests overseen by the Florida Forest Service. There are 35 state forests in Florida covering more than 1,058,000 acres. The first state forest in Florida was Pine Log State Forest, established on 6,960 acres in 1936. Cary State Forest was established in 1937. Blackwater River State Forest and Withlacoochee State Forest were added in the late 1950s and early 1960s.Florida began large land purchase and preservation efforts in the late 1970s and management focus shifted from timber and wildlife focuses to a "multiple land use management ethic" including "conservation of natural and cultural resources, wildlife management, protection of water resources, and outdoor recreation."

Franklin, Virginia

Franklin is an independent city in the Commonwealth of Virginia. As of the 2010 census, the population was 8,582. The Bureau of Economic Analysis combines the city of Franklin with Southampton County for statistical purposes.

Frazier Brook

Frazier Brook is a 7.7-mile-long (12.4 km) stream located in central New Hampshire in the United States. Via the Blackwater and Contoocook rivers, it is part of the Merrimack River watershed. It is subject to the New Hampshire Comprehensive Shoreland Protection Act.

Frazier Brook begins in Danbury, New Hampshire, just south of the town center, and flows south through the town of Wilmot into Andover. Eagle Pond and Bog Pond interrupt the brook's flow. Shortly below Bog Pond, the brook reaches the Blackwater River at the village of Cilleyville.

Frazier Brook is paralleled for most of its length by U.S. Route 4.

Little Blackwater River (Maryland)

The Little Blackwater River is a tributary of the Blackwater River located in Dorchester County, Maryland.

The relatively shallow river is about 15 miles (24 km) long and is surrounded by farms. It is located between Maple Dam Road to the east and Egypt Road to the west. The river begins behind Cambridge-South Dorchester High School in Cambridge, where its water level is nearly 20 feet (6.1 m) above sea level, and it ends below Bucktown.

North Branch Blackwater River (Maine)

The North Branch Blackwater River is a 6.4-mile-long (10.3 km) river in Squa Pan Township (Township 10, Range 4, WELS), Aroostook County, Maine. From its source (46°29′25″N 68°11′29″W), the stream runs west to its confluence with the South Branch to form the Blackwater River. Via the Blackwater River, St. Croix Stream, and the Aroostook River, the North Branch is part of the Saint John River watershed.

River Blackwater (River Loddon)

The River Blackwater is a tributary of the River Loddon in England and, indirectly, of the River Thames. It rises at Rowhill Nature Reserve between Aldershot in Hampshire and Farnham in Surrey and runs northwards to join the Loddon near the village of Swallowfield in Berkshire. Along part of its length, the river forms the boundary between Hampshire and Surrey, and then between Hampshire and Berkshire. It rises in Rowhill Nature Reserve, Aldershot

Rowhill, an isolated remnant of the extensive heathland that once surrounded Farnborough and Aldershot. After 20 miles (32 km) the Blackwater is joined by the River Whitewater near Eversley. The river gives its name to the small town of Blackwater, Hampshire, upon the river near Camberley.

River Blackwater (River Test)

The River Blackwater is a river in the English counties of Hampshire and Wiltshire. It is a tributary of the River Test.

The river rises just to the east of the Wiltshire village of Redlynch, near Salisbury. It then flows east across the county boundary into Hampshire, where it flows north of the village of Wellow and the hamlet of Wigley. The river turns south, passing under the M27 and past Broadlands Lake and the Testwood Lakes reservoirs, before joining the Test between Totton and Redbridge.[1][2] The Environment Agency records the length of the main river as 39.4 kilometres (24.5 mi), with an additional 5.6 km (3.5 mi) for the watercourse from Redlynch to the confluence north of Hamptworth.

South Branch Blackwater River (Maine)

The South Branch Blackwater River is an 8.9-mile-long (14.3 km) river in Aroostook County, Maine. From its source (46°25′23″N 68°08′31″W) in Maine Township 9, Range 3, WELS, the stream runs northwest to its confluence with the North Branch to form the Blackwater River in Squa Pan Township (T. 10, R. 4, WELS). Via the Blackwater River, St. Croix Stream, and the Aroostook River, the South Branch is part of the Saint John River watershed.

Classification systems

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