Page 1

Volume I: Part I: Section 4: Chapter: 3

4.3.1

Section 4: Chapter 3: TaskA4: Collection of Primary Data on Sediment Load 3.1.

Introduction

3.1.3. Hassle

3.1.1. Geography and geology The Satluj River is with extreme slopes and high relief. In areas of high relief, hill slope processes dominate surface geomorphology and can lead to the damming of rivers and formation of lakes upstream. These basins provide a record of natural climatic variations along the river profile and divide the regions in different sedimentation and erosion compartments. The Satluj Valley (32N, 78E) in NW India is dominated by the antecedent Sutlej River, the third-largest river in the Himalayas. 1It flows perpendicular through the orogen and cuts through all major geologic units of the Tethyan Himalaya, High and Lesser Himalayan Crystallines, and Lower Himalayan units. The geomorphologic changes across thrust faults bounding these units provide valuable insights into the evolution of the orogen.

High sediment concentration in the water of Satluj River remains a serious cause of concern which is evident from the rapid siltation of Bhakra Dam Reservoir (Gobind Sagar) and other water bodies. In view of impending energy crisis in the country, several hydro-electric projects were planned both on the main river and its important tributaries.

High silt load caused serious operational problems in the turbines of these projects and hence the need of CAT Plans was felt.

3.1.2. Climate In addition to the geologic and tectonic changes along the Satluj river profile, climate also changes significantly. The high-elevation arid parts of the orogen on the eastern side of Himalayan orographic rainfall barrier at about 3000 m change abruptly into very humid sectors further downstream with mean annual precipitation of 3m. This significant increase in precipitation is also reflected by amplification in sediment flux, hill slope processes, and vegetation cover.

1

Mass Movements, Erosion Patterns And Sediment Transport Along The Sutlej River (NWHimalaya) B. Bookhagen (1), R.C. Thiede (1), M.R. Strecker (1) (1) Institue of Geosciences, University of Potsdam

Five main sources of sediment are well recognized and are as follows: a. Glacial wash/muck triggered by melting of snow on steep mountains This is mainly contributed by Satluj River when it flows through Tibet

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3 and Spiti River which joins Satluj at Khab. Because of steep slope and narrow rocky passage, the velocity is very high and is associated with lot of turbulence in the flow and hence sediment transport power is very high. This problem is specific to snow bound areas above the tree line. Many locals say that the main sources are located in China controlled territory and hence the major part of the problem is beyond our control. In the Indian Territory, much effort to contain the problem has not been made. The options are also limited by terrain and climate imposed limitations. b. Unscientific disposal of debris generated by road construction activity. Himachal Pradesh is a fast developing state where improving road connectivity is very high on the agenda of the Government. The rural roads are being constructed in a very fragile landscape. The highways are being widened by cutting the hills. The hydro-electric projects need to carry heavy machinery and hence need wider roads. The debris thus produced is not properly placed at dump sites and is just pushed on the lower side slopes. This results in heavy erosion during the rainy season contributing silt to the river flow. Ecology and development are in conflict. c.

Landslides and land slips

Weak geology, seismic activity, deforestation, faulty land use and unplanned construction are the main causes of landslides. The earth mass which roles down the slopes or slips down the slope becomes loose and is fast eroded by the rain. NERIL has also noted that at several locations having

4.3.2

irrigated orchards on terraced uplands, the rocky sub-stratum generally had saturated soil profiles. The sub-surface flow moves down the slope and saturates the soil mass located on steep slopes below the orchards. This saturation not only increases the weight of the soil mass but also reduces soil strength upon wetting. This phenomenon becomes the cause of landslides. d. Severe soil drainage lines

erosion

in

the

The rills and gullies on steeply sloping landscapes are deepening and widening under the debris laden high velocity water flow. The landscape denudation and degradation is accentuating the problem of soil erosion in drainage lines. This also includes stream bank erosion in lower reaches. e. Severe soil erosion from common grazing lands/ waste lands Livestock substantially contribute to the economy of hill farmers. The scarcity of forage leads to the problem of illicit and over grazing in the adjoining forests. The common grazing lands are over exploited and hardly support useful fodder trees and grasses. The scarcity of fuel wood leads to cutting/pollarding/chopping of trees and branches. The nomadic glazers with their rights further contribute to the removal of protective vegetation cover thus leading to soil erosion problem. It is now well recognized that well stocked forests, well terraced farm lands and rocky exposed areas are not the only contributors to the soil erosion and sedimentation problems. Even though some amount of soil erosion is inescapable, it is generally within

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3 the permissible limits. It is well known that northern aspects are moist and generally well covered with good forests and vegetation and soil erosion problem is relatively less severe. However, southern aspects are dry, desiccated and devoid of good vegetation and infested with zerophytic and thorny plant species of little economic use. Certain Global trends like the global warming have led to siltation in the Himalayan Rivers. The effects of de-glaciation of the Himalayas can be felt in this region. According to a study carried out by the Wadia Institute of Himalayan Geology, it has been highlighted that in a Himalayan river the glacial content comprises 80 per cent of the silt load. Rapid melting of glaciers has led to an increase in the sediments coming into the rivers from the onset of the melting season.

4.3.3

Hence in order to understand the silt load in our area of project, silt sampling was undertaken. It was carried at various locations in the Satluj River and its tributaries. The methodology adopted for the silt analysis is as per the TOR and is documented hereafter.

3.2.

Silt sampling locations

In order to understand the causes of soil erosion we need to know which region contributes to silt load and therefore a network of nullahs were studied. The locations where silt sampling would be carried out were finalized by the team of experts at NERIL after field visits. About 60 locations were selected for sampling. These sampling sites were given the names of the Khads (streams) in which they were present. Out of the 60 khads at which sampling was carried out, the maximum numbers of sampling locations can be seen in the map given below:

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

Legends Signs

Descriptions Catchment boundary Satluj river Sampling points

Map showing silt sampling locations in Satluj Catchment Area

Comprehensive CAT Plan of Satluj River Basin

4.3.4


Volume I: Part I: Section 4: Chapter: 3

4.3.5

Later, these 60 Khads (streams) were differentiated into 3 regions viz Snow, Snow-monsoon and Monsoon depending on the season pattern they Sr. Sr. Snow region No. No.

have. The list of khads in snow region, snow monsoon region and monsoon region is as follows: Snow – monsoon region

Sr. No.

Monsoon region

1

Spiti River at Losar

21

Rialdang Nala

39

Choling Khad

2

Losar Nala

22

Narado Khad

40

Duling Khad

3

Thuna Nala (Hansa)

23

Chhitkul Nala

41

Ramni Khad

4

Gyundi Nala

24

Kutang khad

42

Panvi Khad

5

Shilla Nala

25

Shushang khad

43

Wangar Gad

6

Rongtong Khad/ Rangrik Khad

26

Shoney khad

44

Solding khad

7

Giew Nala

27

Mansa (Mastrang) Khad

45

Manglad Khad

8

Lingti Khad

28

Gograng khad

46

Sumej Khad

9

Pin River

29

Kharogla Khad

47

Kajo Khad

10

Tabo Nala

30

Seringcha Khad

48

Kuni Gad

11

Lifu Nala/ Leo Khad

31

Hurba khad

49

Broni Khad

12

Spiti at Khab

32

Gungrang khad

50

Nogli Gad

13

Satluj at Khab

33

Rukti khad

51

Kurpan Gad

14

Titang Khad

34

Baspa at Sangla

52

Machhada Gad

15

Chhaso Khad/Ropa Gad

35

Chansu khad

53

Bhaira Khad

16

Gyamthung/Nesang Khad

36

Shong khad

54

Sainj Khad

17

Kirang Khad

37

Brua khad

55

Jajjar Khad

18

Tidong Khad

38

Baturi khad

56

Kingal Khad

19

Kashang Khad

57

Behna Khad

20

Pangi Gad

58

Kotlu Khad

59

Karsog Khad

60

Sainj Khad

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

Sampling site has been demonstrated on map and is displayed below. Layer of tributary network is not shown for clarity. Here the map has been shown

just to have a general idea about the distribution of sampling sites in the study area.

Legends Signs

4.3.6

Descriptions Sub-catchment boundary Satluj river Sampling points

Map showing the sampling locations along with the Sub catchments of Satluj Catchment Area

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3 The map shown below represents the locations of the various Snow, Snowmonsoon and Monsoon regions present

4.3.7

in the Satluj basin. The map shows the maximum regions which can be clearly represented in the map.

Legends Signs

Descriptions Sub-catchment boundary Satluj river Sampling points

Map showing the various sampling sites with regards to their region of occurrence

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3 All above shown map in the form of layers can be seen in SCIS (The GIS application). Each of the 60 Khads (streams) was sampled in such a way that each khad had 15 silt readings. These readings were reported Khadwise and later tabulated. The analysis of the silt load is given hereafter:

Only in case of tributaries of Satluj River namely Baspa and Spiti the sampling is done in more numbers due to the high silt carrying capacity. Sampling season considered here is of monsoon. Dates of sample taken vary based on the monsoon arrival in that location.

3.4. 3.3.

Sampling Methodology

Pattern of Sit sampling location is quite evident from the maps provided but for better clarity schematic view has been displayed below.

4.3.8

Heavy silt carriers and Silt load pattern in Satluj Basin

The graphical illustration of average silt load of all the Khads (streams) for the year 2010 is given below. It is observed that out of the 60 Khads (streams) that were sampled, about 5 Khads (streams) have higher silt i.e. above 2000 ppm. It is also evident that 13 Khads (streams) have negligible average silt value in the range of 1.18-2.8 ppm

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

4.3.9

The Khads (streams) that were reported to have highest (top ten) average silt values are given below:

The graph represents that during the silt sampling in 2010, the tributary of Satluj at Khab has the highest average silt load of 3909.2 ppm which is followed by Chhaso Khad/Ropa Gad which has 3661.86 ppm of average silt. The khad at Baspa (Sangla) which falls under the snow-monsoon region receives 1958.27 ppm of average silt. Whereas the Duling khad which receives water only during monsoons has 1723.82 ppm of silt average in the year 2010.

To know the location of each of these streams in the basin, map is displayed below. It is evident from the map that the river Satluj at Khab receives the highest amount of silt. Out of the 10 Khads (streams) that have reported high average silt load, 8 Khads (streams) are from the Snow region while 1 khad is recorded from Monsoon and 1 khad from Snow-monsoon regions. Thus it can be noted that the erosive power of moving snow is greater than the power of water.

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3 Location of silt sample site having high averages is as follows:

Legends Signs

Descriptions Sub-catchment boundary Satluj river Sampling points Site with highest average silt load

Source: GIS software

Comprehensive CAT Plan of Satluj River Basin

4.3.10


Volume I: Part I: Section 4: Chapter: 3 It can be observed that all above points lie in snow and snow-monsoon region. Thus consistently silt load of such magnitude is carried from these regions to monsoon region. High silt averages are commonly observed in areas having degraded landscape or where no vegetation exists. Population of these regions is very low and so inturn the human interference is also low. Thus the harsh weather conditions and destabilized banks are mainly responsible for the soil erosion. Other natural reasons are the global warming which is causing the rapid deglaciation. As per the TOR, the Khads (streams) which report higher silt values in the

initial 15 readings of sampling are marked. Then for these areas, additional 50 readings of silt are proposed to be taken. Since there is no further demarcation of the Sub catchments into micro-watershed we have not taken the silt samples.

High silt loads Silt data for all the sample locations were studied. To know the highest reading rather highest silt load received in the sampling we sorted out the data and presented it on the map below.

Legends Signs

4.3.11

Descriptions Sub-catchment boundary Satluj river Sampling points Site with highest silt load

Map showing the locations having highest silt loads Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3 The data collected for the silt load indicates that the Satluj at Khab has the highest silt reading of 22286 ppm in the entire sampling season. This is followed by the Spiti at Khab which has the second highest silt reading of 14436 ppm. A difference can be observed in above two maps and that is, High values

Average

Absolute high silt load values

High in snow and snow-monsoon region

Distributed the basin

In low population

In low as well as high population

Natural intervention more

Human interference more

National issues

is

border

in

all

3.5.

4.3.12

Analysis of sampled locations with highest silt load

Sampled locations showing highest average load and lowest average load were selected and pattern of silt load received is being analyzed here. This has helped us in understanding the frequency at which high silt load is being received. Further this has also resulted in speculating the reasons of high average silt obtained in that particular stream. 1. Satluj at Khab

is

More no. of development project and other activities

Silt load received by the river at this point i.e. just after river enters the Indian Border shows highest silt load i.e. 22286 ppm whereas there is a slight fluctuation in silt load in first 13 readings. It can be seen from the graph that there is sudden increase in the silt load, talking to the locals in this region it was realized that large amount of silt loaded water flows from the Chinese side causing unpredicted deluge. This sampling area is present in Sub catchment no. 20 of the Satluj basin.

S a t l u j a t K h A b Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

4.3.13

2. Chhaso Khad/Ropa Gad This tributary is after Titang. The region receives water from the

snow

melt.

The

graph

plotted for Silt data indicates that there is a decrease in silt from 3450 ppm to 1936 ppm from Reading 1 to Reading 3 and later there is increase in silt load upto 9064 ppm on Reading 10.

This

sampling

area

is

present in Sub catchment no 18 of the Satluj basin.

Confluence of Chhaso khad (steam) and Satluj river 3. Spiti at Khab This region receives water from the snow melt. The graph plotted for the silt shows that the silt increases

consistently

from

Reading 1 to Reading 12 i.e. from 878 ppm to 2443 ppm but the silt increases rapidly thereafter and reaches a value as high as 14436 ppm.

This

sampling

area

is

present in Sub catchment no 19A of the Satluj basin

4. Losar Stream This stream lies in the snow region which receives water due to snow melt. During the 15 Reading silt sampling period; it was observed that Reading 1 of silt was as high as 3350 ppm which

experiences

a

gradual Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3 decrease followed by an increase which was followed by reduction of silt upto 978 ppm by Reading 15. Overall, the silt

rate

shows

many

fluctuations

throughout the sampling period. This sampling

area

is

present

in

Sub

catchment no 19F of the Satluj basin.

5. Baspa at Sangla This region receives water from both snow melt and monsoon rains. During the

silt

sampling

period;

it

was

observed that Reading 1 of silt was 637 ppm

which

experiences

a

gradual

increase upto 3707 ppm by Reading 9 which

was

followed

by

gradual

reduction of silt upto 814.1 ppm by Reading 15. The graph drawn appears like an inverted funnel with a distinct peak value. This sampling

area

is

present in Sub catchment no. 7 of the Satluj basin.

6. Giew Nala Out of the 15 readings taken, first 5 readings show subtle decrease in silt while the next 8 readings show gradual increase followed by gradual decrease till we reach Reading 15. This sampling area is present in Sub catchment no. 19B of the Satluj basin.

Comprehensive CAT Plan of Satluj River Basin

4.3.14


Volume I: Part I: Section 4: Chapter: 3 7.

Lifu Nala/ Leo Khad

It is observed that there is a gradual increase in silt from Reading 1 to Reading 10 where the silt readings reach the peak value of 3793 ppm and a gradual decrease in silt is observed upto 857 ppm by Reading 15. The graph shows an inverted funnel shape. This sampling area is present in Sub catchment no. 19A of the Satluj basin.

8. Duling Khad This stream receives water from the monsoon rains. The Reading 1 is 2221 ppm

which

reduces

gradually

upto

Reading 15 to reach a silt load of 971.4 ppm. The reduction in silt readings is very consistent during the sampling period. This sampling area is present in Sub catchment no. 3 of the Satluj basin. 9. Titang Khad The silt at Reading 1 is 4050 ppm which steadily decreases upto 199 ppm by Reading 12 with slight increase in silt reading upto 741 ppm by Reading 15.

Overall

the

readings

decrease

consistently for most portion of the sampling period. This sampling area is present in Sub catchment no. 20 of the Satluj basin.

Comprehensive CAT Plan of Satluj River Basin

4.3.15


Volume I: Part I: Section 4: Chapter: 3 10. Tidong Khad The silt readings produce a perfect curve where the Reading 1 is 100 ppm which increases upto 4214 ppm till Reading

8.Then

the

silt

decrease

gradually upto Reading 15 to reach a value

as

sampling

low

as

area

is

14.2

ppm.

present

in

This Sub

catchment no. 22 of the Satluj basin.

Comprehensive CAT Plan of Satluj River Basin

4.3.16


Volume I: Part I: Section 4: Chapter: 3 3.6.

Analysis of sampled locations with lowest silt load

The Khads (streams) which have extremely low average silt readings are given below: These areas are present mostly in the snow-monsoon region of the Satluj basin. These streams receive water during the snow melt as well as during the monsoon rains. The low silt readings are an indicator of undisturbed landscape. Another reason could be minimum anthropogenic activity like excavation and dumping. 1. Baturi khad This

khad

(streams)

experiences

extremely low silt readings in the range of 0 to 2.5 ppm. From the graph, it can be observed that the silt value on Reading 1 is 0 ppm which reaches 2.2 by Reading 4. Further, the silt reduces steadily upto Reading 15 where it reaches a value of 0 ppm.

2. Gungrang khad It is observed that the Reading 1 readings of silt

are 0

ppm

which

increase upto 1.8 ppm for Reading 2 and

continues

to

change

in

a

haphazard manner till Reading 15.

Comprehensive CAT Plan of Satluj River Basin

4.3.17


Volume I: Part I: Section 4: Chapter: 3 3. Shoney khad The graph drawn during the sampling period shows that the silt reading fluctuates in the initial 6 values of silt and then attains a constant phase during Reading 6 to Reading 9. After Reading

9,

the

silt

load

steadily

reduces upto 1.1 ppm by Reading 15.

4. Hurba khad Reading 1 value of silt is 1.2 ppm which reduces to 0 ppm for Reading 2 and further increases in a haphazard manner upto Reading 10 and then reduces gradually from Reading 11 to Reading 15

5. Solding khad This is the only area which receives water as a result of monsoon rains, yet has low silt readings. The graph drawn has a haphazard shape with several peaks values. The highest silt value during the sampling period is 2.8 ppm for Reading 6. The average silt value for this khad is 1.9 ppm.

Comprehensive CAT Plan of Satluj River Basin

4.3.18


Volume I: Part I: Section 4: Chapter: 3

6. Narado Khad This khad (streams) receives silt in the range of 1.2 to 3.4 ppm. The graph plotted

for

the

sampling

period

indicates that there is a fluctuation in the silt which initially increases till Reading 5 then slightly decreases. The silt values for the last 8 readings are quite constant which reach 2 ppm by Reading 15. The average silt value of this khad is 2.04 ppm.

7. Rukti khad The silt value for Reading 1 is 1.8 ppm which reaches 0 ppm for Reading 2. It is

observed

that

the

silt

value

is

constant from Reading 3 to Reading 9 and increases slightly upto Reading 11 and again attain a constant stage till Reading 15. The average silt value of this khad is 2.05 ppm.

8. Brua khad The silt readings fluctuate in the initial 4 readings of the sampling season. After

Reading

4

the

silt

shows

a

gradual increase till Reading 15 to reach 3 ppm. The average silt value of this khad is 2.1 ppm.

Comprehensive CAT Plan of Satluj River Basin

4.3.19


Volume I: Part I: Section 4: Chapter: 3

Photo of Brua khad

9. Shushang khad This khad (streams) receives silt in the range of 1 ppm to 3.3 ppm during the sampling period. It can be observed from the graph that the silt fluctuates periodically during the sampling period. The average silt load is 2.13 ppm.

10. Kutang khad The silt value is 0 ppm for Reading 1 which is followed by constant rise in values from Reading 2 to Reading 15 of the sampling period. The values of silt are in the range of 0 to 2.7 ppm. The average silt value is 2.2 ppm.

Comprehensive CAT Plan of Satluj River Basin

4.3.20


Volume I: Part I: Section 4: Chapter: 3

4.3.21

11. Chansu khad The

graph

sampling

drawn

shows

an

for

the

silt

increase

in

values from Reading 1 to Reading 9 followed by a reduction in silt load from Reading 10 to Reading 15. Overall it can be noted that the silt values increase during the initial half of the sampling period followed by a distinct fall.

12. Gograng khad The silt value is 0 ppm on Reading 1 which is followed by a distinct rise in value upto 3.8 ppm for Reading 3. Later from Reading 4 to Reading 15, the silt values reduce steadily from 3.5 to 1.5 ppm. The values of silt are in the range of 0 to 3.8 ppm. The average silt value is 2.67 ppm.

13. Shong khad The silt values show fluctuations in the first 5 readings of sampling but, in the next 10 readings, it is observed that

the silt values reduce steadily from 4 to 1.5 ppm from Reading 6 to Reading 15. The average silt value is 2.87 ppm.

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

4.3.22

Analysis of silt data obtained from various Hydro-electric projects

project authority to stop the electricity production when the silt flow reaches alarming levels.

The rivers of Himachal Pradesh have excellent electricity generation potential because of the gradient and velocity. Five perennial rivers viz Satluj, Beas, Ravi, Chenab and Yamuna flow through this state. Thus a number of large and small hydroelectric plants have come up on these rivers. River Satluj has the most HEP and boasts of having the country’s largest HEP viz Nathpa Jhakri HEP.

In order to understand the status of silt flow in the Satluj and its tributaries, NERIL has analysed the silt data for consecutive years upto 2010 obtained from the various HEP. The silt data from 8 different locations is analysed and these locations are as follows:

3.7.

Silt is a limiting factor in the electricity production. The electricity generation is hampered as a result of the heavy silt flows during monsoon and snow melt. This results into huge financial losses especially during the peak production season. Silt also damages the turbines and other moving parts. Thus in order to supervise the silt surge, regular silt monitoring is undertaken at the various HEP that are operational on the Satluj river. This monitoring enables the

o

Baspa at Kuppa

o

Karcham

o

Nirath

o

Jhakri

o

Nathpa

o

Ghanvi

o

Bayal

o

Satluj at khab and Spiti at khab

The map given below shows the locations of the HEP from which the silt data was obtained.

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

4.3.23

3.7.1. Baspa at Kuppa The silt load for 11 consecutive years from 2000 to 2010 has been obtained

and the results are tabulated below and for clarity are represented graphically.

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

Comprehensive CAT Plan of Satluj River Basin

4.3.24


Volume I: Part I: Section 4: Chapter: 3

4.3.25

Analysis of graphs: Sr No

Year

Highest silt month

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

July August July June July July July August July August August

Average Silt reading (ppm) 398.3 218.4 1303.7 616.7 651.9 1050.6 1185.1 2283.9 1087.2 732.8 753.4

It is evident that silt load during these 11 years are greater chiefly during the monsoon months of July and August. The maximum silt load in this area was observed in 2007 in the month of August and was recorded as 2283.9 ppm. On the other hand, minimum silt of 218.4 ppm was recorded in August 2001. 3.7.2. Satluj at Karcham The silt load for 10 consecutive years from 2000 to 2010 has been obtained and the results are tabulated below and for clarity are represented graphically.

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

4.3.26

Analysis of graphs: Sr No

Year

Highest silt month

Average Silt reading (ppm)

1. 2000

July

2590

2. 2001

July

2740

3. 2003

May

1627.4

4. 2004

August

1923.2

5. 2005

July

9731.2

6. 2006

August

5947.8

7. 2007

August

3714.5

8. 2008

June

3556.3

9. 2009

June

3400.1

10. 2010

August

6989.9

It can be observed from the graphs that the silt load in this area is on the higher side. In these 10 years, the average silt load is in the range of 1627.4 to 9731.2 ppm. Maximum silt is observed in the year 2005 in the month of July while May 2003 has the least silt load reported in this area. During these 10 years, the maximum silt yielding months are June-July-August which is mainly the rainy season. 3.7.3. Satluj at Nirath The silt load for 5 consecutive years from 2006 to 2010 has been obtained and the results are tabulated below and for clarity are represented graphically.

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

Analysis of graphs:

4.3.27

Year

Highest silt month

Average reading (ppm)

1.

2006

August

5851.9

2.

2007

August

4708.7

3.

2008

June

3178.5

It can be observed that during the 5 years of silt sampling, the highest silt load in each year is in the range of 2757.1 to 9701.2 ppm. Maximum silt is observed in the year 2010 in the month of August while July 2009 has the least silt load reported in this area. During these 10 years, the maximum silt yielding months are June-July-August which is mainly the rainy season.

4.

2009

July

2757.1

3.7.4. Satluj at Jhakri

5.

2010

August

9701.2

The silt load for 5 consecutive years from 2006 to 2010 has been obtained and the results are tabulated below and for clarity are represented graphically.

Sr No

Silt

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

Analysis of graphs: Sr No

Year

Highest silt month

Average Silt reading (ppm)

1.

2006

August

6179.8

2.

2007

August

4640.7

3.

2008

June

3090.6

4.

2009

July

1847.2

5.

2010

August

8043.3

4.3.28

During these 5 years it is evident that the silt load is maximum during August as compared to the other months of the year. August of 2010 has the highest i.e. 8043.3 ppm of silt. 3.7.5. Satluj at Nathpa dam The silt load for 6 consecutive years from 2005 to 2010 has been obtained and the results are tabulated below and for clarity are represented graphically.

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

Analysis of graphs: Sr No

Year

Highest silt month

Average Silt reading (ppm)

1.

2005

July

11842.2

2.

2006

August

2421.5

3.

2007

August

1469.8

4.

2008

June

1344.1

5.

2009

August

1321.6

6.

2010

April

240.8

4.3.29

It is evident from the graphs that the silt load in July 2005 was extremely high and reached a value of 11842.2 ppm. The silt reading in April 2010 is quite low and has 240.8 ppm of silt. It is observed that the silt reading decreases from 2005 to 2010 which could be as a result of some soil and water conservation measures. As the soil and water conservation measures stabilize over the years, the soil is retained leading to less silt flow. 3.7.6. Ghanvi The monthly silt readings for two years were obtained from this location. Later, these readings were analysed and the results are represented below:

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3 From the above graphs, it is observed that the silt values are extremely low which is an indication of undisturbed landscape. This area either has good forest cover or some soil-water conservation measures are already successfully implemented here.

Analysis of graphs: Sr No

Year

Highest silt month

Average Silt reading (ppm)

1.

2006

August

5903.8

2.

2007

August

4737.8

3.

2008

April

176.1

4.

2009

July

2301.5

5.

2010

August

9201.8

4.3.30

3.7.7. Bayal The silt data for 5 years i.e. 2006-2010 were analysed and the results are represented below:

In the 5 years, it is evident that the silt load decreases initially but later increases. This indicates that some developmental activity was carried out post 2008 which disturbed the equilibrium. 3.7.8. Satluj at khab and Spiti at khab The two rivers: Satluj and Spiti convergence at Khab. The monthly average silt data at both these rivers is collected for the year 2010. The results are:

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3

It is evident from the above graphs that both Satluj and Spiti have high silt loads in the month of August. The silt load in Satluj is higher than that in Spiti.

3.8.

Summary:

Seasonal: From the above data, it can observed that the silt load at various locations is higher during monsoon season. It is during season that most landslips landslides occur.

be the the this and

4.3.31

since it’s commissioning in 2003, the mega project has been crippled by the 'unexpectedly huge amount of silt' coming into its turbines. This has resulted into its forced closure for long periods during the peak generating hours. Consequently there is underproduction of electricity leading to huge financial losses. The project was designed in such a way that it could withstand silt upto 5000 ppm. But it was observed that the silt exceeds 5000 ppm even during non-peak season.

Yearly: Out of all the years data analysed for silt, it is observed that 6 out of 8 locations mentioned above have the highest silt value in the year 2010. This could be as a result of the rapid development taking place in the area. Many hydro-electric plants are coming up in the region. In addition, a number of roads are being constructed by cutting mountains.

3.9.

Conclusion:

The ill effects of siltation can be felt clearly in the Satluj and its tributaries. The several Hydroelectricity projects that are set up in this area are the ones which are the most affected. Even the nation's largest and newest hydroelectric project, the 1,500 MW Nathpa Jhakri Hydel Project on the Sutlej River is not an exception. 2Ever

2

http://www.outlookindia.com/article.aspx?228835, A Dam Squib on Silt Route, Chander Suta Dogra.

Several natural calamities are also responsible for excessive silt load in the Satluj River. An example of this is the breaching of the Pareechoo Lake in China which led to flooding of the Kinnaur region. During this crisis, the silt levels were alarming and reached 1, 51,000 ppm mark. But even after the flood subsided, for days it remained between 20,000 to 30,000 ppm. Based on a 25-year analysis of the silt content in the Sutlej between 1972 and 1996, experts had calculated that silt level beyond the permissible limit (5,000 ppm) in the river would remain high for only four to five days in a year. The experience of the two years (2003-

Comprehensive CAT Plan of Satluj River Basin


Volume I: Part I: Section 4: Chapter: 3 2005) shows that this has been a gross miscalculation—silt beyond 5,000 ppm remains for almost two months. Keeping in mind the alarming rates at which silt load is increasing in the area of study, several bioengineering measures have been proposed. The details of these can be seen in following chapters. Meanwhile as per the ToR based on the silt data we are suppose to prioritize the micro-watershed for its treatment.

Comprehensive CAT Plan of Satluj River Basin

4.3.32

4.3_Task A4_ Collection of Primary Data on Sediment Load_28042011  

In addition to the geologic and tectonic changes along the Satluj river profile, climate also changes significantly. The high-elevation arid...

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