The Mahakam River (
Indonesian
Indonesian is anything of, from, or related to Indonesia, an archipelagic country in Southeast Asia. It may refer to:
* Indonesians, citizens of Indonesia
** Native Indonesians, diverse groups of local inhabitants of the archipelago
** Indonesian ...
: ''Sungai Mahakam'') is third longest and volume discharge river in
Borneo
Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and eas ...
after
Kapuas River
The Kapuas River (or Kapoeas River) is a river in the Indonesian part of Borneo island, at the geographic center of Maritime Southeast Asia. At in length, it is the longest river in the island of Borneo and the longest river of IndonesiaMacK ...
and
Barito River
The Barito River is the second longest river in Borneo after the Kapuas River with a total length of and with a drainage basin of in South Kalimantan, Indonesia. It originates in the Muller Mountain Range, from where it flows southward int ...
, it is located in
Kalimantan
Kalimantan () is the Indonesian portion of the island of Borneo. It constitutes 73% of the island's area. The non-Indonesian parts of Borneo are Brunei and East Malaysia. In Indonesia, "Kalimantan" refers to the whole island of Borneo.
In 2019, ...
,
Indonesia
Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guine ...
. It flows from the district of
Long Apari in the highlands of Borneo, to its mouth at the
Makassar Strait
Makassar Strait is a strait between the islands of Borneo and Sulawesi in Indonesia. To the north it joins the Celebes Sea, while to the south it meets the Java Sea. To the northeast, it forms the Sangkulirang Bay south of the Mangkalihat Pe ...
.
The city of
Samarinda
Samarinda is the capital city of the Provinces of Indonesia, Indonesian province of East Kalimantan on the island of Borneo. The city lies on the banks of the Mahakam River with a land area of . Samarinda ranks first on East Kalimantan Human dev ...
, the provincial capital of
East Kalimantan
East Kalimantan (Indonesian: ) is a province of Indonesia. Its territory comprises the eastern portion of Borneo. It had a population of about 3.03 million at the 2010 census (within the current boundary), 3.42 million at the 2015 census, and 3. ...
, lies along from the river mouth.
The delta Mahakam river consist of specific micro climate which is influenced by high and low tide at sea level.
Summary
The Mahakam Rive
is the largest river in East Kalimantan, Indonesia, with a catchment area of approximately 77,100 km
2. The catchment lies between 2˚N to 1˚S latitude and 113˚E to 118˚E longitude. The river originates in Cemaru from where it flows south-eastwards, meeting the River Kedang Pahu at the city of
Muara Pahu. From there, the river flows eastward through the Mahakam lakes region, which is a flat tropical lowland area surrounded by peat land. Thirty shallow lakes are situated in this area, which are connected to the Mahakam through small channel
Downstream of the connection with the Semayang and Melintang lakes, the Mahakam meets three other main tributaries – the rivers Belayan, Kedang Kepala, and Kedang Rantau – and flows south-eastwards through the Mahakam delta distributaries, to the Makassar Strait.
Geology
Kalimantan, where the Mahakam lies, is part of the
Sunda Plate, Sunda Continental Plate. The large island has mountain ranges between Indonesia and Malaysia. As described by van Bemmelen (1949), River Mahakam rises in Cemaru () in the center of
Kalimantan
Kalimantan () is the Indonesian portion of the island of Borneo. It constitutes 73% of the island's area. The non-Indonesian parts of Borneo are Brunei and East Malaysia. In Indonesia, "Kalimantan" refers to the whole island of Borneo.
In 2019, ...
, from there it cuts through the pre-tertiary axis of the island east of the Batuayan () and then reaches the tertiary
basin of Kutai. Its middle course traverses a lowland plain with many marshy lakes. This intermontane depression is separated from the neighboring basin, the
Barito depression Barito may refer to:
*Barito River, a big drainage basin in South Kalimantan, Indonesia
*Barito languages, around twenty Dayak (Austronesian) languages of Borneo, Southern Philippines. Also Malagasy, the national language of Madagascar.
**East Bari ...
, by a broad hilly tract of less than altitude. After this region, the Mahakam cuts through the Samarinda
anticlinorium
In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...
and reaches its alluvial delta, which spreads like a broad fan over the shelf-sea, with a base of and a radius of about .
Upstream of Long Iram (upstream part of Mahakam river basin) the river is flowing in
tertiary
Tertiary ( ) is a widely used but obsolete term for the geologic period from 66 million to 2.6 million years ago.
The period began with the demise of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start ...
rocks (Voss, 1983). Between
Long Iram and Muara Kaman (middle Mahakam area) the river is flowing in
quaternary
The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million years ...
alluvium
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...
, while in the downstream area between
Muara Kaman and the coast including the Mahakam delta, tertiary rocks are again present. The presence of the large delta is explained by the formation and rejuvenation of the hilly region near
Samarinda
Samarinda is the capital city of the Provinces of Indonesia, Indonesian province of East Kalimantan on the island of Borneo. The city lies on the banks of the Mahakam River with a land area of . Samarinda ranks first on East Kalimantan Human dev ...
.
Climate
The Mahakam catchment is around the equator. The average annual rainfall in the catchment area is 3163 mm. The average runoff is around 1911 mm. According to
Köppen climate classification
The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, notabl ...
, this area belongs to type Af (tropical rainforest) that has a minimum temperature ≥18 °C and precipitation of the driest month in normal year ≥60 mm Transfer of mass and energy in the tropical zone occurred through general air circulation known as the
Hadley cell
The Hadley cell, named after George Hadley, is a global-scale tropical atmospheric circulation that features air rising near the equator, flowing poleward at a height of 10 to 15 kilometers above the earth's surface, descending in the subtropics, ...
. According to Seidel et al. (2008) the
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
pattern in this area is largely determined by this large-scale atmospheric wind patterns, which is observable in several ways throughout the atmosphere. This circulation carries moisture into the air, generating rainfall in equatorial regions, whereas at the edges of the tropical belt are drier. Within this circulation, evaporation occurs intensively around the equator on the center of low pressure called the
Intertropical Convergence Zone
The Intertropical Convergence Zone (ITCZ ), known by sailors as the doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the thermal e ...
(ITCZ), characterized by accumulation of cloud in the area. The ITCZ moves following the pseudo-motion of the sun within 23.5°N and 23.5°S zone, therefore its position always changes according to this motion.
The ITCZ drives the Indo-Australian
monsoon
A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscil ...
phenomena which influence the regional climate including the Mahakam catchment. In December, January, February (winter in Northern Hemisphere) the concentration of high pressure in Asia and low pressure in Australia make the west wind blows in Indonesia (west monsoon). In June, July, August concentration of low pressure in Asia (summer in Northern Hemisphere) and concentration of high pressure in Australia make the east wind blows in Indonesia (east monsoon). Due to the global air circulation and the regional climate mentioned above, the Mahakam catchment which is located around the equator has a bimodal rainfall pattern with two peaks of rainfall, which are generally occurred in December and May. This is because the ITCZ passed through the equator twice a year, from the Northern Hemisphere in September and from the Southern Hemisphere in March.
Lakes
There are about 76 lakes spread in the Mahakam river basin and about 30 lakes are located in the middle Mahakam area including the three main lakes (Lake Jempang 15,000 Ha; Lake Semayang 13,000 Ha; Lake Melintang 11,000 Ha). The lakes levels are seasonally fluctuated from 0.5 m – 1 m during dry period to seven meters during rainy season. The Mahakam lakes and surrounding wetlands act as water storag
as well as a trap of sediment contained in the water flowing into the lakes which are now known to become shallower, presumably as a result of an imbalance between sediment input and slow subsidenc
Fishing is the primary source of livelihood in the Mahakam lakes area, most of the people around the lakes are fishermen. The middle Mahakam lake area is an area of intensive fishing activity with a productivity of 25,000 to 35,000 metric tons per year since 197
Delta
![nypha](https://upload.wikimedia.org/wikipedia/commons/c/cd/Nypha.jpg)
The Mahakam delta is a mixed
fluvial
In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviog ...
-
tidal
Tidal is the adjectival form of tide.
Tidal may also refer to:
* ''Tidal'' (album), a 1996 album by Fiona Apple
* Tidal (king), a king involved in the Battle of the Vale of Siddim
* TidalCycles, a live coding environment for music
* Tidal (servic ...
dominated delta. The delta covers about , consisting of
mangrove
A mangrove is a shrub or tree that grows in coastal saline water, saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evoluti ...
areas near the shore,
Nypa swamps in the central areas, and lowland forest near the apex, corresponding to the first bifurcatio
Fishery development in this area has converted a vast area of mangrove into shrimp ponds (tambak). However, recent
mangrove restoration
Mangrove restoration is the regeneration of mangrove forest ecosystems in areas where they have previously existed. The practice of mangrove restoration is grounded in the discipline of restoration ecology, which aims to “ ssistthe recovery of ...
efforts have taken place in the delta by replanting mangroves in abandoned shrimp ponds and encouraging
silvofishery.
Many areas in the Mahakam delta are already naturally recolonized by mangrove vegetation contributing to ecosystem restoration. Mangroves also function as
sedimentation enhancing strategies
Sedimentation enhancing strategies are Environmental resource management, environmental management projects aiming to restore and facilitate land-building processes in River delta, deltas. Sediment availability and deposition are important because ...
by capturing sediment causing
accretion
Accretion may refer to:
Science
* Accretion (astrophysics), the formation of planets and other bodies by collection of material through gravity
* Accretion (meteorology), the process by which water vapor in clouds forms water droplets around nucl ...
.
The delta has three main
distributaries
A distributary, or a distributary channel, is a stream that branches off and flows away from a main stream channel. Distributaries are a common feature of river deltas. The phenomenon is known as river bifurcation. The opposite of a distributary ...
system directed Northeast, Southeast and South. The area between distributaries consists of a series of tidal channels generally unconnected to the main distributaries. The distributary channels are narrow and rectilinear with the depth ranging from and distributary channel bifurcations appear every .
This lower Mahakam area is the second most productive hydrocarbon basin of Indonesia which contains around 3 billion barrels of oil and 30 Tcf of gas reserves. Field geological investigations in this area was started in 1888 and in 1897 exploration drilling discovered oil at shallow depth of on the Louise structure. Production started in 1898 followed by expansion of exploration to the entire Mahakam.
Ecology
![jempangbird](https://upload.wikimedia.org/wikipedia/commons/4/47/Jempangbird.jpg)
Mahakam and its floodplain is an ecologically important region. A total of 147 indigenous freshwater fish species had been identified from the Mahakam. The Mahakam hosts the freshwater dolphin
Irrawaddy dolphin
The Irrawaddy dolphin (''Orcaella brevirostris'') is a euryhaline species of oceanic dolphin found in scattered subpopulations near sea coasts and in estuaries and rivers in parts of the Bay of Bengal and Southeast Asia. It closely resembles the ...
(''Orcaella brevirostris''; called Pesut by local people) a critically endangered species, which is included on
CITES
CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...
(Convention on International Trade in Endangered Species of Wild Fauna and Flora) Appendix
The Mahakam river basin is also an important breeding and resting place for 298 bird species, among them 70 protected and five endemic species: Borneo dusky mannikin (''Lonchura fuscans''), Borneo whistler (''Pachycephala hypoxantha''), Bornean peacock-pheasant (''Polyplectron schleiermacheri''), Bornean blue-flycatcher (''Cyornis superbus'') and Bornean bristlehead (''Pityriasis gymnocephala''
br />
A research cluster
: "Upsetting the balance in the Mahakam Delta: past, present and future impacts of
sea level rise
Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...
, climate change, upstream controls and human intervention on sediment and mangrove dynamics" extensively carry out research on the Mahakam. The cluster's objective is to study the impact of external forcing factors such as sea-level rise, climate change, upstream sediment, as well as human interference on past, present and future development of the Mahakam delta in different time scales.
Pollution
Logging and mining activities have contributed to the "alarming rate" of pollution of East Kalimantan's Mahakam River. Tests of water pollutants showed levels increased sharply between 2009 and 2011. Despite the growing pollution, it is claimed that "the water is basically still safe for consumption."
Unsafe concentrations of heavy metals have been observed in Mahakam fish. A 2015 study found lead concentrations in excess of 1000 times safe levels along with unsafe levels of copper, zinc, and cadmium.
Bridges
Bridges include the
Mahakam Bridge and the
Kutai Kartanegara Bridge. The latter collapsed on 26 November 2011, it took 3 years of planning and one and half years more to rebuild new bridge on the same spot. The new Kutai Kertanegara Bridge has been open for public use since 8 December 2015, after an opening ceremony held by a local regent.
Social aspect
![Ponton coal](https://upload.wikimedia.org/wikipedia/commons/4/4c/Ponton_coal.jpg)
The River Mahakam is an economic resource for fishermen and farmers, and as freshwater source, as a waterway since ancient time until today. It is in this river basin where the
Kutai
Kutai is a historical region in what is now known as East Kalimantan, Indonesia on the island of Borneo and is also the name of the native ethnic group of the region (known as ''Urang Kutai'' or "the Kutai people"), numbering around 300,000 who ...
kingdom evolved. The Kutai history is divided into two periods, Kutai Martadipura (around 350–400 AD) and Kutai Kartanegara period (around 1300). Kutai Martadipura, a Hindu kingdom founded by Mulawarman at Muara Kaman, is regarded as the oldest kingdom in Indonesia. Kutai Kartanegara was founded by settlers from Java at Kutai Lama near the mouth of Mahakam. In around 1565, Islam was extensively spread in Kartanegara by two Moslem preachers from Java, Tunggang Parangan and Ri Bandang.
The
Dayaks
The Dayak (; older spelling: Dajak) or Dyak or Dayuh are one of the native groups of Borneo. It is a loose term for over 200 riverine and hill-dwelling ethnic groups, located principally in the central and southern interior of Borneo, each wi ...
are the indigenous people inhabiting Kalimantan beside the Kutais and the Banjars. Since the 1970s
transmigration of people to East Kalimantan was organized by the Indonesian government especially in areas near River Mahakam. Transmigration aims to migrate people from overpopulated
Java
Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...
,
Bali
Bali () is a province of Indonesia and the westernmost of the Lesser Sunda Islands. East of Java and west of Lombok, the province includes the island of Bali and a few smaller neighbouring islands, notably Nusa Penida, Nusa Lembongan, and Nu ...
, and
Madura
Madura Island is an Indonesian island off the northeastern coast of Java. The island comprises an area of approximately (administratively 5,379.33 km2 including various smaller islands to the east, southeast and north that are administrati ...
islands to stimulate greater agricultural productivity in outer islands. By 1973, almost 26% of the land under cultivation in East Kalimantan was being worked by transmigrants.
[Babcock, 1986 as cited by Stadtmueller T., 1990. Soil erosion in East Kalimantan, Indonesia. Proceedings of the Fiji Symposium Research Needs and Applications to Reduce Erosion and Sedimentation in Tropical Steeplands, June 1990: IAHS-AISH Publ. No.192,1990.]
References
{{Coord, 0, 35, S, 117, 17, E, display=title, region:ID_type:river_source:GNS-enwiki
Rivers of East Kalimantan
Landforms of East Kalimantan
Rivers of Indonesia