16
WATERSHEDS PRIORITIZATION AND MANAGEMENT PLANNING USING GIS: A
STUDY OF THE CATCHMENT AREA OF MAHANANDA RIVER, WEST BENGAL, INDIA
Souvik Kundu
Independent Scholar, University of Kalyani, Kalyani, Nadia, West Bengal, India
Email: souvik.kgc.2012@gmail.com

How to cite this paper:
Kundu,
Souvik(2021)
Watersheds Prioritizationand Management Planning
using GIS: A Study of theCatchment
Areaof
Mahananda River, West
Bengal, India, Journal of
Global Resources, Vol. 07
(02)
DOI:
10.46587/JGR.2021.v07i02.016

Received: 21 March 2021
Reviewed: 10 April 2021
Revised: 26 April 2021
Final Accepted: 22 May 2021

Abstract: As watershed management and Soil conservation
are two sides of a coin, both are needed to pay attention
simultaneously in the context of socio-economic development
as well as environmental sustainability also. This present
research work is going to emphasise on the watershedmanagement of the seven sub-watersheds (SWs) of thesource catchment area of Mahananda River considering thedifferent parameters of three main geomorphic aspects
namely, linear aspects, relief aspect and areal aspects as well
as different Land use/ Land Cover pattern also with using
Digital Elevation Model and satellite images in GIS
environment. The results of such prioritization reveal that
SW4, SW5 and SW6 have needed highest priority as theiraverage priority index ranges in between 2.65 to 3.79; themoderate priority should be given to SW1and SW7 and thelowest priority for SW2 and SW3, basis of which, watershedmanagement planning should be done.
Keywords: Areal Aspects, Average Priority Index, Digital
Elevation Model, Linear Aspects, Relief Aspects.

Freely available Online

www.isdesr.org

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Introduction
Socio-economic development through the use of environmental resources should be always
in a sustainable manner but uncontrolled access of resource leads environmental degradation.
The agricultural practices and deforestation with growing population is increasing day by day
in the source catchment of Mahananda River (Kiran, 2013). This condition is responsible forhuge amount of soil erosion and hence, well watershed management planning is required. As
several research works (Puno and Puno, 2019; Iqbal and Sajjd, 2014; Balasubramanian et al.,2017)has represented watershed management planning through sub-watersheds
prioritization, this present research work is also going to represent a watershed management
planning considering relevant geomorphic and land use/ land cover parameters in GIS
environment. After dividing the whole catchment area into a number of sub-watersheds, thevarious geomorphic parameters underline a respects, relief aspects and areal aspects
combined with LULC parameters like forest cover, built-up area, agricultural land etc. should
be considered for their ranking and on the basis of compound factor, watersheds are prioritized(Puno and Puno, 2019).The research work of Iqbal and Sajjad (2014) represented that theland use and land cover under built-up, water bodies, agricultural land and barren land
categories are directly proportionate with soil erosion while land under forest cover, tea
plantation etc. are inversely proportionate. In the areal aspects, Drainage Density, Stream
frequency and Drainage Textures are directly proportionate with high run off and highprioritization, in the relief aspects, average slope and relative relief are also directly
proportionate (Balasubramanian et al., 2017). Not only Drainage and Relief features, shape ofthe sub-watersheds is also important as the peak of runoff varies due to geometry ofwatersheds (Iqbal and Sajjd, 2014).
Objectivesi.
To prioritize the sub-watersheds on the basis of geomorphic and LULC parameters.
ii.
To analyse the compound factor of all sub-watersheds and their chances of soil erosion
for watershed management planning.
MATERIALS AND METHODS
Study Area
The source catchment area of Mahananda River is situated at Darjeeling district, West Bengal,of which longitudinal and latitudinal extensions are ranges in between 88◦17’ E to 88◦ 27’ E and26◦55’ N to 26◦41’ N respectively (Figure-1). This river is the only one in north Bengal whichflows towards south west direction due to tectonic controls from springs in Dow Hill Forest (asriver Mahanadi) and meet with Balason River up to which the study area is selected(Kumar,
Kumar and Shrivastava, 2020). The catchment area of this river is 245.48 sq. km and the mean
estimated discharge in Monsoon season is more than the other seasons (Rudra, 2016).
Materials
This research work is totally dependent on secondary data. Elevation data (Cartosat-1, PAN,
2.5m spatial resolution) and satellite image (Resourcesat-2, LISS-III, 24m spatial resolution
dated 12nd November, 2017) of the study area has been collected from Bhuvan (National
Remote Sensing Centre, ISRO).
Methods“Channel Network and Drainage Basin” algorithm was used for watershed delineation andstream ordering in QGIS software. After that important geomorphic parameter of eachwatershed have calculated and analysed by using following formulas (Table-1).

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Table 01: Geomorphic Parameters and Formulas
Geomorphic Parameters
Stream Ordering
Bifurcation Ratio (Rb)
Stream Length Ratio (Rl)Relative Relief (Rr)
Dissection Index (Di)Average Slope (Sa)Drainage Density (Dd)Stream Frequency (Fs)
Drainage Texture (T)Form Factor (Rf)Elongation Ratio (Re)FormulasHierarchical methods
Rb= Nu/ N (u+1)
Rl= Lu/ L(u – 1)
Rr= Hmax- hmin
Di= Rr/ Absolute Height
Sa= tan-1(N X i)/ 636.6
Dd= LK/ AK
Fs=Number of streams / areas
T= Dd X Fs
Rf = A/ L2
Re= ‫ﬨ‬R2/ 4

Sources
Strahler (1964)
Schumm (1956)
Horton (1945)
Smith (1935)
Nir (1957)
Wentworth (1930)
Horton (1945)------Horton (1945)
Horton (1932, 1945)
Schumm (1956)

Nu is number of streams in a given order; N (u+1) is number of streams of the next higher order; L u is total lengthof the all streams in a given order; L(u – 1) is total length of the all streams of next lower order; H max = maximum
height; hmin = minimum height; N is number of contour crossing; i is contour interval; L K is the total length of all
streams in given area; AK is area; A is basin area; L is basin length and R is the result of Basin area is divided
by basin length.

All the watersheds are ranked on the basis of above-mentioned parameters andsummed up for compound factor which is further divided by the number of parameters forgeomorphic priority index calculation. Thereafter, Land use/ Land Cover map of theMahananda catchment area is prepared by supervised classification methods of satellite
image. After classification, areas under different LULC categories of each watershed are
calculated and LULC prioritization has been done on the basis of their ranking. After all, overall
priority of each watersheds has been calculated by average value of both geomorphic and
LULC priority index. Depending on overall priority index, watershed management planning will
be done.
RESULTS AND DISCUSSIONS
Linear Aspects
Bifurcation Ratio (Rb) and Stream Length Ratio (Rl) of each sub-watershed has been calculatedon the basis of number of streams of each order and their length (Table-2 & 3). According toStrahler (1964), all the stream segments which have no tributaries are considered as first order
Journal of Global Resources, July 2021, Volume 07 (02) Souvik Kundu Page 157 | 9

stream and when two first order streams meet with each other into a single stream then thiswill be categorised as second order streams (Figure-2). Two second order streams will bemerged into third order and so on (Strahler, 1956).
Table 02: Order-Wise Stream Length of All Sub-Watersheds
SW
1
2
3
4
5
6
7
Total

1st Order
17
14
10
59
54
41
28
224

Number of Streams
2nd Order
3rd Order
4th Order
10
4
9
3
6
2
16
15
17
24
10
18
23
17
16
11
104
66
32

5th Order

23

19

Table 03: Order-wise Stream Numbers of all Sub-watersheds
SW
1
2
3
4
5
6
7
Total

1st Order
17.59
8.66
12.68
44.94
44.07
31.32
27.01
186.27

Stream Length (km.)
2nd Order
3rd Order
4th Order
6.19
4.02
0.00
6.44
0.81
0.00
4.76
0.68
0.00
14.49
18.58
18.20
20.57
11.77
13.01
28.95
16.33
0.00
13.57
6.52
0.00
95.00
58.71
31.21

5th Order
0.00
0.00
0.00
10.96
0.00
0.00
0.00
10.96

Bifurcation Ratio (Rb)
In this case, SW1, SW2 and SW3 have recorded with higher bifurcation ratio and remaining
sub-watersheds have recorded comparatively low (Table-4). This scenario focus on the more
geological disturbance of upper catchment areas while the middle and lower partcomparatively lower disturbed areas.
Stream Length Ratio (Rl)
Here, SW2, SW3 and SW7 represent with comparatively lower Stream length ratio whichmeans the difference in slope gradient amongst the areas with different stream orders is low
and SW1, SW4, SW5 and SW6 have greater difference in slope gradient (Table-4).
Relief Aspects
Relative Relief (Rr)
SW1 has highest relative relief as 1835 metres and some others high undulated watersheds(SW3, SW2 and SW4) have recorded also high relative relief. Lowest relative relief has beenrecorded in SW7. Lower relative relief reveals comparatively less chances for river erosional
activities while higher values draw special attention to check the soil erosion (Table-4).

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Table 04: Quantified Geomorphic Parameters of All Sub-watersheds
SW

1
2
3
4
5
6
7

LinearAspects
Rb
Rl
2.100 1.112
2.278 0.768
2.333 0.528
1.594 0.980
1.735 1.012
1.568 1.206
1.602 0.789

Relief Aspects
Rr
1835
1245
1576
1068
738
687
158

Di
0.848
0.753
0.788
0.950
0.914
0.916
0.712

Sa
20◦1’16’’
21◦15’4’’
18◦37’59’’
11◦23’1’’
7◦35’39’’7◦21’21’’1◦52’39’’

Area Aspects
Dd
1.217
1.251
1.400
1.655
1.496
1.702
1.718

FS
1.358
2.045
1.390
2.007
1.773
1.799
2.006

T
1.652
2.559
1.946
3.321
2.653
3.061
3.447

Rf
0.474
0.864
0.459
0.122
0.298
0.176
0.170

Re
0.777
1.049
0.765
0.393
0.615
0.474
0.466

Figure 02: Stream Ordering
Dissection Index (Di)
SW1, SW4, SW5 and SW6 have higher value and need more attention for soil conservation
while remaining watersheds deserve lower priority in this sense (Table-4).
Average Slope (Sa)
SW1, SW2, SW3 and SW4 have comparatively higher average slope combining with higher
relative relief, enhance the probability of more soil erosion with increasing the potential energyof streams’ water and remaining watersheds with lower average slope (ranges in between 1
to 7 degrees) are represented as less chances for erosional works (Table-4).
Areal Aspects
Drainage Density (Dd)
SW7, SW6 and SW4 are recorded as higher drainage density. Due to lower undulating surface
coupled with less permeability of the ground layers and less vegetation cover while in thenorthern and north-eastern parts has recorded with low density as their have low chances towidely distribute due to more undulating surface and high vegetation cover (Table-4).

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Figure 03: Relative Relief

Figure 05: Drainage Density

Figure 04: Average Slope

Figure 06: Stream Frequency

Stream Frequency (Fs)
SW2, SW7 and SW4 have higher number of streams as 2.045, 2.007 and 2.004 streams per
square kilometres respectively while the remaining have lower frequency. Higher frequency
results more soil erosion with higher relief, lower vegetation and less permeable rocks (Table4).
Drainage Texture (T)SW4, SW6 and SW7 represent very fine drainage texture which influence more run off andmore erosional activities while SW5 and SW2 have moderately coarse and remaining has
more coarse drainage texture. SW1 and SW3 have greater vegetation cover and for this thedrainage texture becomes coarse in this area (Table-4).

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Form Factor (Rf)
It varies from 0 to 1. If the value is nearer to 1 that means the shape of basins more circularand if it is near about 0 then it reveals the elongated shape of the basins (Choudhari, et al.,2018). Here, SW2, SW1 and SW3 are represented as circular forms which have less chance
to get higher peak of discharge in short duration and less run off. SW4 has lowest value andrepresented as elongated basins with maximum chances for erosions. The remaining watershades are also closer to elongated nature (Table-4).
Elongation Ratio (Re)If the value of this ratio is closer to 0 then the basin will be identified as highly elongated (Puno
and Puno, 2019).Here all the watersheds (except SW1, SW2 and SW3) are fallen into thisgroup which has less chances for erosional work. On the other hand, the northern watershades are more circular and are needed more attention in the sense of soil conservation(Table-4).

1
2
3
4
5
6
7

Rank of Watersheds on the basis of Geomorphic Parameters

Rb

Rl

Rr
(m.)

Di

Sa

Dd

FS

T

Rf

Re

3
2
1
6
4
7
5

2
6
7
4
3
1
5

1
3
2
4
5
6
7

4
6
5
1
3
2
7

2
1
3
4
5
6
7

6
7
5
3
4
2
1

7
1
6
2
5
4
3

7
5
6
2
4
3
1

6
7
5
1
4
3
2

6
7
5
1
4
3
2

Geomorphic
Priority Index

SW

Priority

CompoundFactorTable 05: Prioritization of Watersheds on the basis of Geomorphic Parameters

44
45
45
28
41
37
40

4.4
4.5
4.5
2.8
4.1
3.7
4.0

Low
Low
Low
High
Moderate
High
Moderate

Prioritization on the Basis of Land use/ Land Cover (LULC) Parameters
The overall pattern of LULC reveals SW1, SW2, SW3 and SW5 get lower priority as large
forest cover helps to check extensive soil erosion and southern watersheds (namely, SW7,
SW4, SW6 and SW5) get higher priority due to Built-up area, Open grass land, Silted area,
Agricultural land and Water bodies are also highly concentrated. Though other factors of
Barren land and Tea plantation also influence soil erosion in northern part but dominating forest
cover decrease the priority of northern watersheds (Table-6). The result shows that SW4, SW5
and SW7 have high priority while SW3 has low priority and SW1, SW2 and SW6 arerepresented as moderate priority (Table-7).
Table 06: Percentage of Different LULC Areas
SW

1
2
3
4
5
6
7

Percentage of Area under Different Major Categories of Land use/ Land CoverOpen
Forest Silted Agricultural Barren
Tea
Water
Built-up
Grass Land
Area
Land
Land
Plantation
Bodies
Area
5.60
5.67
5.08
8.88
5.41
11.69
39.89

69.13
77.93
63.52
44.65
68.52
51.21
7.84

0.15
0.01
0.24
4.97
2.92
2.78
2.47

0.67
0.19
1.29
3.23
0.64
8.43
7.46

10.61
7.95
16.90
7.54
3.77
7.86
3.54

10.29
5.46
11.14
2.01
2.18
3.38
2.35

2.32
2.27
1.01
5.20
4.47
1.94
0.93

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1.22
0.53
0.82
23.53
12.08
12.71
35.52

Figure 07: Land use/ Landcover Map of Mahananda Catchment Area.

Barren Land

Tea
Plantation

Water Bodies

6
7
5
1
2
3
4

3
1
4
5
2
7
6

2
3
1
5
6
4
7

6
5
7
1
2
4
3

3
4
6
1
2
5
7

5
7
6
2
4
3
1

36
38
40
20
29
31
30

Priority

Agricultural
Land

6
7
4
2
5
3
1

CompoundFactor

Silted Area

5
4
7
3
6
2
1

Built-up Area

Forest

SW1
SW2
SW3
SW4
SW5
SW6
SW7

Open GrassLand

Rank of Watersheds

Priority Index

Table 07: Prioritization of Watersheds on the basis of LULC

4.500
4.750
5.000
2.500
3.625
3.875
3.750

Moderate
Moderate
Low
High
High
ModerateHigh

Prioritization on the Basis of Morphometric and Land use/ Land Cover Parameters
Geomorphic priority index of SW4 and SW6 draw special attention as their Dissection Index,
Form factor, Elongation ratio, Drainage texture, Stream frequency, Stream length ratio andDrainage density represent more vulnerable conditions. Moreover, minimum forest cover andmaximum area under settlement and water bodies of these watersheds comparing to otherwatersheds are also responsible for higher LULC priority index. The land use and land coverengaged with forest, plantation and agriculture protects soil from erosional work. So, thewatersheds with higher areal coverage with such parameters will be given lower priority andvice versa. On the other hand, higher coverage of open land, barren land, built-up areas, silted
area and water bodies lead to higher priority and vice versa (Iqbal and Sajjad, 2014).
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Table 08: Prioritization of Watersheds on the basis of both Geomorphic and LULC
Parameters
Geomorphic Priority
Index
4.4
4.5
4.5
2.8
4.1
3.7
4.0

SW1
SW2
SW3
SW4
SW5
SW6
SW7

LULC Priority
Index
4.50
4.75
5.00
2.50
3.62
3.88
3.75

Average Priority
Index
4.45
4.63
4.75
2.65
3.86
3.79
3.88

Overall Priority
Moderate
Low
Low
High
High
High
Moderate

Conclusion
The average value of geomorphic and land use/ land cover priority index of each watershed
are considered as overall priority (Table-8) which represents highest priority to SW4 and lowest
priority to SW3. There is total three watersheds namely SW4, SW5 and SW6 which should
give more attention for soil conservation due to especially high drainage density, drainage
texture and stream frequency with low vegetation and high concentration of settlement. For
these conditions, the population, lumbering of these three watersheds should be checked anddams should be constructed which will help extensive run off and regular supply water for
agriculture. SW1 and SW7 have marked as moderate priority zone. Though these twomoderate priority zones have needed to give more priority in the context of relief and areal
aspects but LULC parameters and form factors (like maximum vegetation coverage, medium
concentration of settlement, form factor and elongation ratio) decrease the priority. At the trijunction point of SW1, SW2 and SW3, a water reservoir with check dam should be constructedwith considering geological conditions which helps agriculture of the southern part as well as
soil conservation in the northern part also.
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