The Digul River () is a major

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

South Papua South Papua, officially the South Papua Province (), is an Indonesian Provinces of Indonesia, province located in the southern portion of Western New Guinea, Papua, following the borders of the Papuan customary region of Anim Ha. Formally establ ...

province,

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

, on the island of

New Guinea New Guinea (; Hiri Motu: ''Niu Gini''; , fossilized , also known as Papua or historically ) is the List of islands by area, world's second-largest island, with an area of . Located in Melanesia in the southwestern Pacific Ocean, the island is ...

. It is the fourth longest river in New Guinea after

Sepik The Sepik () is the longest river on the island of New Guinea, and the third largest in Oceania by discharge volume after the Fly River, Fly and Mamberamo River, Mamberamo. The majority of the river flows through the Papua New Guinea (PNG) provi ...

, Mamberamo, and Fly. With a total length of and a

drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...

of .

Course

The river originates in the central part of the island, on the southern side of the

Maoke Mountains The Maoke Mountains is a mountain range in the province of Central Papua and Highland Papua. It extends over 692 km and is composed of the Sudirman and Jayawijaya ranges. It is part of the larger New Guinea Highlands The New Guinea Highla ...

(Digul or Star Mountains), which rise above sea level at 4,700 m. After leaving the mountainous section, it cuts through lowland swamps in a south-southwest direction and then flows by delta into the

Arafura Sea The Arafura Sea (or Arafuru Sea) lies west of the Pacific Ocean, overlying the continental shelf between Australia and Western New Guinea (also called Papua), which is the Indonesian part of the Island of New Guinea. Geography The Arafura Sea is ...

, across Dolak Island. Its marshy, swampy floodplain is lined with reed beds. As there are no accessible and developed roads in the area, the river is still the only transport route across the marshes to the fertile hills and mountains in the interior of the island. It is navigable by larger boats from Tanahmerah (320 km) and by smaller boats from the foot of the mountains. This swampy navigable stretch is often referred to as ''Boven-Digul''. Its length as the crow flies from its source to its mouth is relatively short, but it follows a very winding course over flat land to the sea.

History

The swamplands upstream were known by the name " Boven-Digoel" (Above the Digul, in Dutch) and hosted a penal colony at Tanahmerah (Red Earth) in the early 20th century, when Indonesia was a colony of Holland. As a result of the abortive 1926 revolt by the

Communist Party of Indonesia The Communist Party of Indonesia (Indonesian language, Indonesian: ''Partai Komunis Indonesia'', PKI) was a communist party in the Dutch East Indies and later Indonesia. It was the largest non-ruling communist party in the world before its Indo ...

(PKI), the Dutch exiled 823 of the most troublesome revolutionaries here.Brackman, A.C., Indonesian Communism: A History, 1963, Praeger Press

Geography and hydrology

Rising on the southern slopes of

, the Digul flows first south and then west to empty into the

. For much of its length, it travels across a low region of extensive swamps and creates a

delta Delta commonly refers to: * Delta (letter) (Δ or δ), the fourth letter of the Greek alphabet * D (NATO phonetic alphabet: "Delta"), the fourth letter in the Latin alphabet * River delta, at a river mouth * Delta Air Lines, a major US carrier ...

near Dolak (Yos Sudarso Island, formerly Frederik Hendrik) Island. The river has a length of and is navigable as far as Tanahmerah. Together with the Mappi, which joins its northernmost delta, it collects the waters of an area of about 45,000 square kilometres. The river flows in the southern area of Papua with predominantly

tropical monsoon climate An area of tropical monsoon climate (occasionally known as a sub-equatorial, tropical wet climate or a tropical monsoon and trade-wind littoral climate) is a tropical climate subtype that corresponds to the Köppen climate classification category ' ...

(designated as ''Am'' in the Köppen-Geiger climate classification) and

tropical rainforest Tropical rainforests are dense and warm rainforests with high rainfall typically found between 10° north and south of the Equator. They are a subset of the tropical forest biome that occurs roughly within the 28° latitudes (in the torrid zo ...

(designated as ''Af'' in the Köppen-Geiger climate classification) transitional type, with an annual rainfall of 3,500–4,000 mm. The annual average temperature in the area is 22 °C. The warmest month is April, when the average temperature is around 24 °C, and the coldest is June, at 20 °C. The average annual rainfall is 3,072 mm. The wettest month is January, with an average of 464 mm rainfall, and the driest is July, with 28 mm rainfall. The average rainfall for the whole catchment area between 2002 and 2011 was 3,522 mm.

Delta

Its delta is a relatively new tidal delta in development with wide and deep delta branches and channels. The intermittent tides reach 5–7 metres. The delta is changing rapidly from year to year (new channels and delta branches) due to the high sedimentation process (clay deposits, sedimentary silt) on the banks. The delta is rich in fauna and, although navigable, very sparsely populated.

Ecology

The Digul catchment has a rich and diverse fauna. Around 100 endemic species are found here ( Paradisaea apoda, Ptilinopus perlatus, Chelodina novaeguineae, Centropus violaceus, Alcedinidae, etc.). The mud islands of the delta are covered with marsh and forest vegetation. The dominant species are

mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...

( Avicenia alba,

Rhizophora apiculata The tall-stilt mangrove (''Rhizophora apiculata'') belongs to the Plantae kingdom under the Rhizophoraceae family. ''R. apiculata'' is distributed throughout Southeast Asia and the List of islands in the Pacific Ocean, western Pacific islands. ...

mahogany Mahogany is a straight- grained, reddish-brown timber of three tropical hardwood species of the genus ''Swietenia'', indigenous to the AmericasBridgewater, Samuel (2012). ''A Natural History of Belize: Inside the Maya Forest''. Austin: Universit ...

( Xylocarpus moluccensis),

nipa palm ''Nypa fruticans'', commonly known as the nipa palm (or simply nipa, from ) or mangrove palm, is a species of palm native to the coastlines and estuarine habitats of the Indian and Pacific Oceans. It is the only palm considered adapted to the ...

(

Nypa fruticans ''Nypa fruticans'', commonly known as the nipa palm (or simply nipa, from ) or mangrove palm, is a species of palm native to the coastlines and estuarine habitats of the Indian and Pacific Oceans. It is the only palm considered adapted to the ...

), marsh plant (

Bruguiera cylindrica ''Bruguiera cylindrica'' is a small tree in the mangrove family Rhizophoraceae, native to tropical Asia and Australia. It was first described in 1827 and has the conservation status of least concern. Description ''Bruguiera cylindrica'' is a sm ...

) and their hybrids ( Rhizphora mucronata).

Discharge

*Monthly flow (m³/s):

Tributaries

The main tributaries from the mouth: ^*Period: 1971–2000

References

{{Rivers in Indonesia Landforms of Western New Guinea Rivers of South Papua Digul basin