The Dhansiri River of Northeast India: An Overview of Its Geography, Ecology and Importance

Dhansiri River

The Dhansiri river is a major tributary of the Brahmaputra river in Northeast India. It originates from the Laisang peak in the state of Nagaland at an altitude of about 800 m above MSL. The total length of the Dhansiri river is approximately 352 km as it flows from south to north before joining the Brahmaputra river on its south bank at Dhansirimukh.

Hereby, the UCN Team offers a comprehensive analysis, giving you key concepts and insights into the importance of River Dhansiri.

The Dhansiri river is fed by several tributaries on its course including Dayang, Diphupani, Khora, Langlong and Beopani. It drains almost the entire western and southern parts of Nagaland as it flows through the state. The total catchment area of the Dhansiri river basin is around 12,584 sq km in the plains.

Geography

dhansiri river map
dhansiri river map

Origin and Course

The Dhansiri river originates from the Laisang peak located in the state of Nagaland at an altitude of around 800 meters above mean sea level. From its source, the river initially flows in a north-westerly direction for the first 40 km.

Thereafter, the Dhansiri river flows north-east for about 76 km until it reaches the city of Dimapur in Nagaland. Beyond Dimapur, the river changes its course and flows in a northerly direction. It continues its northerly flow for around 240 km before meeting the Brahmaputra river on its south bank at Dhansirimukh in Assam.

The total length of the Dhansiri river from its origin at Laisang peak to its confluence with the Brahmaputra river is approximately 352 km. The Dhansiri river is the main river flowing through the Golaghat district of Assam and Dimapur city of Nagaland..

Tributaries

The major tributaries feeding the Dhansiri river are Dayang, Diphupani, Khora, Langlong and Beopani.

River Dhansiri Map
River Dhansiri Map
Subansiri RiverKopili River
Dhansiri RiverLohit River
Dibang RiverSiang River
Brahmaputra River

Catchment Area

The total catchment area of the Dhansiri river basin is around 12,584 sq km in the plains. The river drains almost the entire western and southern parts of the hilly state of Nagaland as it flows through the region.

Major tributaries arising from the hills of Nagaland like Dayang, Diphupani, Khora, Langlong and Beopani feed the Dhansiri river, thereby draining large parts of the western and southern areas of the state.

Hydrology

The Dhansiri is an important perennial river in Northeast India and the prime river of Golaghat district in Assam as well as Dimapur city in Nagaland.

In the 113 km stretch between the Morongi Tea Estate and the Brahmaputra river confluence, the Dhansiri river has an average width of about 150 meters. The depth of the river in this stretch varies from 6 to 8 meters approximately.

The discharge of the Dhansiri ranges from a minimum of 4.88 cubic meters per second to a maximum of 209 cubic meters per second, with an average of around 513 cubic meters per second, as measured at the Numaligarh gauging station.

Pollution and Conservation

Pollution

Certain stretches of the Dhansiri river have been identified as polluted, particularly near Golaghat and Numaligarh in Assam. The main pollution load in the river comes from domestic waste and sewage generated from Dimapur city in Nagaland.

There is a lack of proper sewage treatment facilities in Dimapur, resulting in direct discharge of untreated sewage and municipal waste into the Dhansiri river and its tributaries. This has led to high organic pollution levels in the river water.

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Agricultural runoff containing pesticides and fertilizers is a source of chemical toxins entering the Dhansiri river. Erosion of topsoil during heavy monsoon rains also leads to heightened turbidity and increased sediment loads. Effluent discharge from industries situated close to Dimapur city adds inorganic pollutants and hazardous substances to the river. Furthermore, sand mining operations in the river have detrimental impacts on the riverbed ecology and water quality. The cumulative effect of these activities degrades the aquatic environment of the Dhansiri river.

Conservation Efforts

To control pollution and rejuvenate the Dhansiri river, the government has formed a River Rejuvenation Committee (RRC).

Several projects have been sanctioned by the Ministry of Environment, Forests and Climate Change for sewage and solid waste management infrastructure in Dimapur city.

These pollution abatement measures aim to improve the water quality of the Dhansiri river to make it fit at least for bathing and irrigation purposes along its stretch. The target is to bring the Biochemical Oxygen Demand (BOD) level below 3 mg/l and fecal coliform levels within 500 MPN/100 ml.

Ecology

Several ecological studies have been conducted on the Dhansiri river to analyze its biodiversity and aquatic life. The river harbors diverse planktonic life including species of phytoplankton, zooplankton and periphyton.

The benthic macro-invertebrates observed in the river include insects like mayflies, beetles, stoneflies as well as annelid worms and molluscs.

Around 34 fish species belonging to 24 genera and 13 families have been identified in the Dhansiri river, with Cypriniformes being the dominant order. Some key fish species found are Tor, Botia dario, Amblyceps apangi, and Channa species.

Navigation

The Dhansiri river has been declared as a National Waterway by the Inland Waterways Authority of India (IWAI). As part of this, IWAI conducted a Stage 1 feasibility study on a 113 km stretch of the river from Morongi Tea Estate to the Brahmaputra confluence.

The study analyzed the river’s prospects for navigation and transportation of cargo and passengers. It provides a base for detailed investigation of sustainable navigation development on this important river.

Final Thoughts

In the UCN team’s opinion, the Dhansiri is an important perennial river in Northeast India that originates in Nagaland and flows through Assam to join the Brahmaputra river. With a total length of about 352 km and catchment area of 12,584 sq km, the Dhansiri drains major parts of central and western Nagaland.

The river is ecologically diverse, supporting many species of fish, plankton and aquatic life. However, pollution from untreated sewage is a major concern, especially near urban centers like Dimapur. Conservation efforts are ongoing to control pollution levels and improve the water quality of the Dhansiri river.

Being the prime river of the Golaghat and Dimapur districts, the Dhansiri holds ecological and economic significance in the region. With the river identified as a National Waterway, its potential for navigation and transportation may be tapped in a sustainable manner for regional development. The Dhansiri thus remains an important lifeline in Northeast India that requires integrated management for water resource and environmental sustainability.

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