This document discusses using remote sensing to estimate water discharge in Himalayan rivers. It begins by explaining the importance of measuring water discharge but limitations of conventional gauge-based methods. It then outlines how remote sensing approaches can establish width-discharge relationships based on a threshold theory of channel formation. Applying this to Landsat images of several Himalayan rivers allows estimating total discharge across multiple channels as well as generating hydrographs without in-situ gauges. In conclusions, the study finds its width-discharge method is valid for both single-thread and multiple-thread rivers and could be applied to estimate average annual discharge in other alluvial rivers globally.
3.4 IUKWC Workshop Freshwater EO - Kumar Gaurav - Jun17
1. Remote sensing to estimate formative water
discharge of the Himalayan Foreland rivers.
Department of Earth & Environmental Sciences
Indian Institute of Science Education and Research, Bhopal
(India-UK Water Centre)
19 June 2017
Kumar Gaurav (IISER, Bhopal) Remote sensing to estimate discharge 0 / 14
2. Introduction
Flow discharge and its measurement:
Q=?
v
Water discharge in river
channels is an important
quantity of hydrologic cycle
Kumar Gaurav (IISER, Bhopal) Remote sensing to estimate discharge 1 / 14
3. Introduction
Flow discharge and its measurement:
Q=?
v
Water discharge in river
channels is an important
quantity of hydrologic cycle
It is needed to understand:
- Terrestrial water budget
- Flood management
- River morphology
- Water security etc.....
Kumar Gaurav (IISER, Bhopal) Remote sensing to estimate discharge 1 / 14
4. Introduction
Flow discharge and its measurement:
Q=?
v
Water discharge in river
channels is an important
quantity of hydrologic cycle
It is needed to understand:
- Terrestrial water budget
- Flood management
- River morphology
- Water security etc.....
Kumar Gaurav (IISER, Bhopal) Remote sensing to estimate discharge 1 / 14
7. Discharge estimation: Conventional approach
Stage-Discharge rating curve:
(x10)
30 60 90
0
20
10
0
Discharge (Q)
Depth(H)
Flow H
[source: Sanders 1998]
Site dependent
Requires a gauging station
Assumes river ๏ฌows as
single-thread and have a
stable boundary
Kumar Gaurav (IISER, Bhopal) Remote sensing to estimate discharge 3 / 14
8. Discharge estimation: Conventional approach
Stage-Discharge rating curve:
(x10)
30 60 90
0
20
10
0
Discharge (Q)
Depth(H)
Flow H
[source: Sanders 1998]
Site dependent
Requires a gauging station
Assumes river ๏ฌows as
single-thread and have a
stable boundary
Flo
w
Flow
Flow
?
Kumar Gaurav (IISER, Bhopal) Remote sensing to estimate discharge 3 / 14
9. Discharge estimation: Remote sensing approach
Width-Discharge rating curve:
Discharge
Width
0 1000 2000
400
800
(Q)
(W)
[source: Smith et al., 1996]
At a station rating
curves.
Assumes river is stable.
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10. Alluvial river: channel migration
Channels are mobile in
space and time
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11. Width-discharge relationship: Physical basis
Threshold theory
ยต =
Tangential force
Normal force
ยต is Coulomb friction coe๏ฌcient
For a given discharge this
mechanism sets the size of a
channel.
[Glover and Florey 1951, Henderson 1963, and Seizilles et al 2013]
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12. Threshold theory: regime relations
W =
ฯ
ยต3/4
3
23/2 K [1/2]
โ
Cf
g1/4
1
L1/4
โ
Q (Laceyโs law)
L =
ฮธt (ฯs โ ฯf ) ds
ยตฯf
W and Q are width and discharge
ฮธt is threshold parameter
ds is grain size
Cf is Chรฉzy friction coe๏ฌcient
ยต is Coulombโs friction coe๏ฌcient
ฯf and ฯs is ๏ฌuid and water density
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13. Himalayan foreland rivers and threshold channel: width
10
1
10
2
10
3
10
4
Discharge [ ]
10
1
10
2
10
3
Width[m]
Multiple Single channel
Threshold
theoryBest ๏ฌt
[Gaurav et al, 2017 (In press)]
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15. Locations
0 650 km
Indus
Brahmaputra
Indo-Gangetic Basin River
0 650 km
Himalayan Frontal Thrust
Indus
Brahm
aputra
Chenab
Ganges
Kosi
Teesta
N
Bhimnager barrage
Panjnad
Kotri barrage
Farakka barrage
Anderson br
Kaunia
Bahadurabad
Paksay
Data
Landsat satellite images (resolution 30 m)
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16. Discharge at a section
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17. Discharge at a section
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18. Discharge at a section
Total discharges;
Qtot = Q1 + Q2 + Q3
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19. Hydrograph
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
10
2
10
3
10
4
Discharge[m3
sโ1
]
Kosi Bhimnagar barrage
Image derived
Average
In-situ
Average
Month
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20. Conclusions
Average annual discharge can be estimated using remotely sensed
images.
Width-Discharge regime relation established in this study is equally
valid for multiple and single-thread river system.
This ๏ฌnding could be extend to alluvial rivers located in di๏ฌerent
environments worldwide.
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