Teesta River

Presented by-Md. Inzamul Haque

Ms. StudentDepartment of Geography & Environment

Shahjalal University of Science & Technology, Sylhet-3114

Past, Present and Future Prospect

• Origin: Pauhunri glacier, Zemu Glacier, Lake Cholamu, Lake Gurudongmar Location: Sikkim, India; Elevation: 7,068 m (23,189 ft) • Countries: India, Bangladesh

• State: Sikkim, West Bengal, Rangpur

• Length: 309 sq. Km (192mi)

• Basin Area: 12,540 km2 (4,842 sq mi)

Introduction

Teesta is the fourth main river in terms

of discharge in Bangladesh

Origin & Course of Teesta River

Pahunri Glaciar(Sikkim)>Rangpo(Siliguri)>Teesta

Bazar(Darjeling)>Jalpaiguri>Kuchbihar>Niphamari>Lal

monirhat>Rangpur>Kurigram>Gaibanda>Brahmaputra

River

Teesta River BasinThe transboundary basin of the Teesta River encompasses 12,159 square kilometers, of which 10,155 are in India and 2,004 are in Bangladesh. Approximately 8,051 square kilometers of the river basin lie in hilly parts of Sikkim (6,930 square kilometers) and West Bengal (1,121 square kilometers). Approximately 4,108 square kilometers of the basin lie in the plains of West Bengal (2,104 square kilometers) and Bangladesh (2,004 square kilometers).

Historically, the Teesta was part of the Ganges river system, flowing south from Jalpaiguri in West Bengal in three separate channels: the Karatoya, the Purnabhaba, and the Atrai. It is speculated that the three channels led to the name “Trisrota” (“possessed of three streams”) and subsequently to “Teesta.” Following a flood in 1787, the Teesta changed its course southeast to join the Brahmaputra.

Himalayan part: The Teesta drains nearly 95 percent of the mountainous state of Sikkim. Within a distance of 100 kilometers, the elevation of the Teesta basin varies from 8,598 meters to 213 meters. As it travels towards the plains, the Teesta is joined by a number of tributaries, including the Lachung Chhu, the Dik Chhu, the Chakung Chhu, the Rani Khola, and theRangpo on the left bank, and the Zemu, the Rangyong, the Rongli, and the Rangit on the right bank.

Sub Himalayan part: In the sub Himalayan plains, the Teesta is joined by tributaries such as the Leesh, the Geesh, the Chel, the Neora, and the Karala. From Melli Bazar in down stream Sikkim, the river leaves the hills and enters the plains of West Bengal at Sevoke near Siliguri.

Northern Plain: In total, the Teesta flood plain covers nearly 14 percent of the total cultivated area of Bangladesh and provides livelihood opportunities directly to approximately 7.3 percentof the population, or 9.15 million people, in five districts of Rangpur Division(Gaibandha, Kurigram, Lalmonirhat, Nilphamari, and Rangpur).

Teesta River Basin

Teesta River Morphology(Cathment area)

• At the time of Major Rennel's survey, the mainstream of the Teesta followed south instead of south-east as at present, joined the Atrai in Dinajpur and finally fell into the Ganges.

• In the destructive flood of 1787, which formed an epoch in the history of Northern and Central India, the stream suddenly forsook its course and opened a new channel to the southeast into the Brahmaputra.

• Local minor changes in its course occur more often. The latest shift of this type took place during the period 1960-62 when the main channel changed from Gaddimari on the left bank, opening a new channel downstream of Dalia on the right bank.

• The present course of the river from international border to the down of Kaunia railway bridge flows over the ridge dividing the Atrai-Karotoya-Teesta valley from Brahmaputra basin, thereby its course always experience instability.

Teesta River Morphology(Historical Change in River Course)

Teesta River Morphology(Historical Change in River Course)

An analysis has revealed that during the

14 years(1984-1997) under review, the

river has shifted quite appreciably (2840

meters) towards the west in the middle

part of the reach between the Indian

Border and 15 Km upstream of the Kaunia

Railway Bridge. At 15 Km upstream of the

Kaunia Bridge the situation is just the

opposite and the shifting is towards the

northeast by about 3409 meters.

The shifting around the Barrage has been

restricted by the bank protective

measures that have been done to safe

guard the Teesta Barrage.

Teesta River Morphology(River Bank Shifting)

* On the basis of data from 1970 to 1990-

• the average discharge during June to September, observed at Dalia, is about 1,800 cusec,

while that of winter and dry months is only 200 cusec.

• Flow is lowest in the month of February and seldom exceeds 160 cusec.

• Withdrawal at the Indian barrage at Gozaldoba located about 99.0 Km upstream from the

Teesta Barrage may be a probable reason of the flow reduction.

* Minimum discharge in monsoon season was 71.73 cusecs in 1979 and maximum water

discharge was 1825.86 cusecs in 1999.

* In dry season the maximum water discharge was 158.49 cusecs and 5.36 cusecs in 1997 and

in 1988 respectively.

Teesta River Morphology(Water Discharge)

Teesta River Morphology(Water Discharge)

Water level vs. Discharge

Teesta River Morphology(Water Flow)Teesta River water flow condition till 1994 was in a balance condition compared to the water flow condition of 1979. After the year of 1994 conspicuous decreaseof water flow condition at Dalia point was noticed. This gradual decrease water flow trends became worst in the year of 2010 when it was near 1.5%. As the water flow condition is going down day by day, so it will be dry in most recent years.

Teesta River Morphology(Erosion & Deposition)

• According to a study, net deposition at Teesta river was about 2.5x10^5m3 in 18 years.

• It is observed from the present study that the Teesta River bed is being aggradated (depositon) at a rate of 100 mm per year at the upstream of the Tista Barrage since it's construction. The immediate downstream part of the river from the Barrage will suffer degradation(Erosion) at the rate of 200 mm per year.

• The most erosion prone area is the stretch between the Barrage and 15 km downstream, just upstream of the confluence of the Buri Teesta River. It is seen from both the mathematical model results and the planform analysis that severe erosion will continue to happen in the future until the river has reached an equilibrium state.

Water Quality

Water quality refers to the chemical, physical, biological, and radiological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which compliance can be assessed.

The Water quality of tributary streams of Teesta is meeting the desired criteria for Conductivity, DO and pH. pH is meeting the desired criteria except few locations. But BOD ranges from 0.3 -6.2 mg/l and is not meeting the criteria at all the locations. Study shows that BOD level in Teesta Basin is increasing between 2010 (4.4) and 2011

(6.2). The higher values of Fecal Coliform (39x10^4MPN/100ml) & Total Coliform

(225x10^3MPN/100ml) is observed at River Teesta at Siliguri and Karola, d/s of Jalpaiguri. D.O. : Dissolved Oxygen; BOD: Biochemical Oxygen Demand

Station Code

D.O. (mg/l) B.O.D. (mg/l) pH CONDUCTIVITY(µmhos/cm)

min max mean min max mean min max mean min max mean

> 4 mg/l < 3 mg/l 6.5-8.51801Sikkim

20.0 26.0 23.1 2.3 3.4 2.6 5.9 7.0 6.5 250 280 268

1807Sikkim

16 28 20.2 3.3 4.4 3.9 5.5 7.0 6.3 260 320 293

1808Sikkim

14 24 19.3 4.0 4.5 4.3 6.0 6.5 6.1 260 300 283

1809Sikkim

14 14 18.6 3.5 3.5 4.3 6.0 6.5 6.2 270 310 288

1947West B

8.0 10.0 8.6 0.3 6.2 2.9 7.0 7.9 7.3 108 114 111

1806Sikkim

16.0 25.0 20.9 3.2 4.5 3.8 6.0 6.5 6.2 240 300 283

Water Quality(D.O., B.O.D., pH, Conductivity)

Geographical Intensity of Teesta River Basin

Major Hydroelectric Projects & Dams in Teesta River BasinThe successfully completed major projects and dams are:1. Teesta -V dam, the largest project so far, was completed in 2007 on Teesta. Its height is 87 metres (285 ft) and its length is 176 metres (577 ft). It generates 510 MW hydroelectric power and assists flood control.

2. Rangit III hydroelectric project was completed in 2000 on Greater Rangit River which is a tributary of Teesta River. The catchment area of Rangit III dam is 979 square kilometres (378 sq mi) and the dam is 47 metres (154 ft) high. The project has 60 MW generation capacity, and is already online.

3. The Tista Barrage is a major irrigation project in Bangladesh, in Lalmonirhat District. Construction started 1979 and was completed in 1997-98.

The other three completed projects are significantly smaller and minor—Lower Lagyap, Upper Rongni Chhu and Mayang Chhu projects.

Importance of Teesta River• The Teesta River has an average annual runoff of 60 billion cubic

metres (BCM). 90% of the river’s flow occurs during the monsoon or wet season i.e. between June and September. The importance of the flow and seasonal variation of this river is felt during the lean season (October to April/May) when the average flow is about 500 million cubic metres (MCM) per month.

• About 21 million Bangladeshi people live in the basin of river Teesta while only 8 million live in West Bengal and half a million live in Sikkim state. The population ratio is 70 for Bangladesh and 30 for India. This river water is being used in various sector of human life including livelihood, irrigation, fisheries and household uses. Around 70% of these people of northern part of Bangladesh are directly dependent on the river for their livelihood.

• The basin is primarily agrarian. Crops grown include rice, wheat and maize with other supplementary crops like rubber and tea. Other economic sectors are tourism and small-scale industries dependent on agricultural raw materials.

Irrigation Target-Achivement at Teesta Flood Plain Region

Major Sources of Threat to Freshwater Resources

Watershed Disturbance• Cropland• Imperviousness• Livestock density• Wetland disconnectivity

Pollutants• Soil salinization• Nitrogen loads• Phosphorus loads• Mercury deposition• Pesticide loads• TSS loads• Organic (BOD) loads• Potential for acidification• Thermal impacts

Water Resource Development• Small dam density• River network fragmentation• Consumptive use (loss/supply)• Water crowding (population/supply)• Cropland per unit supply• Residency time change (large

dams)

Biotic Threats• Invasion level (non-native fish)• Non-native fish species richness• Catch pressure• Aquaculture

23 Threats Under 4 Broad Themes

Major Issues • A case study in the TBP area suggests that the present flow in the Teesta River is inadequate to meet

the present irrigation requirement, while the fluctuation in the flow rate affects directly the availability of water in the flood plain area.

• The irrigation water availability from the river has been always less than that planned. Unilateral withdrawal of Teesta water by India upstream limits irrigation water availability in the TBP area. India plans to link thirty major rivers including the Teesta River for diverting water to her water-scarce southwest. Unilateral diversion of water from these trans-boundary rivers, which provide about 85% of fresh water flow in the dry season, will impede agricultural production and damage the local ecosystem.

• The shallow aquifers underlying the floodplain are the only sources of freshwater during the dry season. The interrelationship between the surface and groundwater resources of the deltaic plain suggests that changes in the rate of the Teesta River water flow, affects directly the availability of groundwater.

• Reduction in flow in both Ganges and Teesta will affect the whole western part of the country.

• River Bank Erosion: (Over 200 families of two villages made homeless in Gaibandha in six days: Daily Star; July 19, 2013), (River erosion wreaks havoc in Kurigram: Dhaka Tribune; Oct 24, 2014)

Agriculture and Water

“Engineered”water

Sanitation & Access to Clean Water

Climate change and its extremes

Over Exploitation of Freshwater Resources

Water Quality

Urban waters

Other common Uses & Issues

Irregular and Devestating Flood Deforstation

Management of Teesta River Basin

There have to engineering approaches for river management-1. Hard Engineering Approach2. Soft Engineering Approach

 Examples of hard engineering- Channelization, to raise,

straighten or strengthen banks

dams and weirs diversion channels dredging retention basins and

balancing lakes artificially raising the height

of the floodplain

Examples of soft engineering- Afforestation Floodplain zoning Land-use management, e.g.

Contour ploughing Wetland and riverbank

conservation River restoration Improved forecasting and warning