Welcome development: River basin wise rainfall maps from IMD!

30-rbwc

We have noticed during just concluded South West monsoon season that IMD (India Meteorological Department) has started a new and welcome feature in rainfall data reporting[i]. The Data is available in maps, on daily, weekly and seasonal basis. We are not sure when this practice started, we noticed it only during 2016 monsoon season.

This is most welcome development, since getting rainfall data at basin level is most appropriate and useful, since basin is the hydrological unit that will experience the impact of rainfall or lack of rainfall in the basin, in form of floods or droughts. It can also be very useful for flood forecasting and preparedness, among many other uses. We hope IMD will develop and refine this further.

In each map, the actual rainfall for the given period is given for each basin, as also the normal rainfall & % departure from normal. Usual colour code is used to show the basin as blue if rainfall is more than 120% of normal rainfall, green if rainfall is 81-119 %, brown if rainfall is 60-80% of normal and yellow if rainfall is below 60% of normal rainfall.

In these maps, IMD has divided the country into about 59 river basins/ sub basins. Considering India’s total area of 3.287 m sq km, this means each basin on an average has area of 55712 sq km. This is still fairly large area. In fact, some of these 59 basins (e.g. Nagvali, Vamsadhara, Kynchiang, Tons, Imphal & Others) have about or below 10000 sq km area, which is much better. So there are others (e.g. Upper and Lower Brahmaputra, Ghaggar, Luni-Saraswati-Bhadar, Chambal, Narmada, Bhagirathi (Bengal), West flowing rivers south of Tapi, all the way to Southern tip of Kerala, among others) with areas close to or over 1 lakh sq km. It would be good if these are broken into smaller sub basins in future for reporting rainfall data. Ideally, no sub basin should have area more than 10 000 sq km to begin with.

In the table below, we have provided data from these maps for some of these weeks and cumulatively for the monsoon season till July 19 and also till Sept 30 (full monsoon season, see the last column).

River basin wise Rainfall data 2016 South West Monsoon

River Basin/ GROUP

Sub Basin 19 July Cum[ii] 20-27

July[iii]

28 July -03 Aug 04-10

Aug

18-24

Aug

01-07

Sep

08-14

Sep

15-21

 Sep

30 Sep Cum[iv]
Indus[v] Chenab 386.8 (89) 43.5

(-39)

48.5

(-43)

12.5

(-81)

62.0

(15)

98.0

(195)

27.5

(-18)

14.0

(-13)

1156.9

(64)

Upper Sutlej 271.8 (30) 25.8

(-53)

76.1

(53)

75.8

(63)

55.5

(54)

15.2

(-47)

13.4

(-52)

2.4

(-87)

655.7

(14)

Lower Sutlej 169.0 (10) 27.1

(-40)

26.4

(-41)

32.3

(-27)

22.6

(-34)

10.4

(-62)

5.5

(-77)

15.6

(26)

420.1

(-12)

Ravi 198.3 (-6) 30.9

(-55)

58.1 

 (-31)

83.9

(14)

7.5

(-85)

17.5

(-48)

3.4

(-89)

9.6

(-66)

521.9

(-27)

Ghaggar 167.6 (16) 18.9

(-55)

42.2 (21) 43.9

(18)

11.8

(-63)

5.3

(-78)

2.4

(-88)

3.1

(-71)

399.7

(-7)

Ganga Upper Ganga 454.9 (52) 83.2

(-9)

102.0 (11) 76.2

(-10)

21.9

(-71)

45.3

(-19)

17.6

(-63)

7.3

(-78)

978.6

(1)

Ramganga 389.6 (21) 97.4

(22)

109.5 (24) 60.5

(-25)

15.1

(-81)

17.2

(-68)

28.3

(-47)

2.8

(-92)

883.5

(-11)

Ghaghara 354.7 (-8) 71.9

(-15)

85.4  

(-2)

18.9

(-73)

15.6

(-81)

24.0

(-60)

60.4

(-15)

31.2

(-37)

826.4

(-24)

Gomti 280.5 (-2) 57.0

(-9)

81.1 (20) 32.5

(-51)

50.0

(-27)

35.4

(-33)

51.8

(-24)

31.9

(-27)

818.7

(-7)

Kosi 322.5 (-25) 94.3

(-32)

36.1

(-54)

17.3

(-68)

7.0

(-90)

119.1

(126)

81.5

(42)

64.7

(38)

929.7

(-15)

Gandak 332.5 (-5) 44.3

(-27)

35.0  

(-49)

31.6

(-45)

59.9

(-10)

102.0

(104)

75.8

(29)

42.0

(-15)

925.7

(-2)

Damodar 324.7 (-18) 48.0

(-32)

49.2

(-36)

91.7

(24)

167.4

(165)

142.7

(109)

79.4

(17)

34.5

(-24)

1130.3

(5)

Sone 353.2 (-1) 49.1

(-34)

65.1

(-20)

72.3

(-20)

147.9

(94)

52.1

(-27)

59.4

(-11)

22.3

(-45)

1201.8

(15)

Tons 521.4 (75) 45.6

(-40)

60.3

(-27)

51.2

(-43)

236.8

(230)

16.2

(-77)

37.6

(-47)

31.1

(-19)

1450.0

(51)

Ganga 261.6

(17)

14.1

(-73)

80.3

(26)

24.3

(-65)

56.4

(-14)

22.7

(-51)

16.6

(-70)

24.1

(-28)

690.8

(-9)

Bhagirathi-Bengal 639.1 (34) 233.5

(180)

59.4

(-22)

44.9

(-33)

68.3

(-1)

130.5

(99)

65.4

(-11)

72.5

(26)

1553.3

(28)

Yamuna Upper Yamuna 238.2 (1) 13.3

(-80)

55.3

(-13)

30.4

(-56)

23.3

(-62)

15.6

(-62)

0.2

(-99)

3.0

(-85)

541.5

(-27)

Middle Yamuna 289.4 (83) 8.2

(-84)

86.8

(99)

24.6

(-58)

63.9

(34)

25.9

(-33)

0.3

(-99)

0.4

(-98)

603.7

(5)

Lower Yamuna 380.8 (53) 28.3

(-60)

67.5

(-5)

61.0

(-31)

102.8

(52)

10.3

(-82)

2.8

(-95)

16.8

(-54)

810.6

(-6)

Chambal 322.0 (56) 29.0

(-58)

122.6

(124)

152.9

(135)

117.6

(102)

32.3

(-33)

4.1

(-86)

18.9

(16)

913.7

(33)

NORTH EAST INDIA

 

Upper

Brahamputra

664.7 (-10) 204.9

(88)

40.4

(-54)

76.4

(-7)

17.5

(-80)

172.2

(127)

84.4

(-2)

55.9

(-28)

1514.5

(-5)

Lower

Brahamputra

1065.1 (23) 419.3

(259)

58.8

(-42)

37.2

(-59)

54.8

(-44)

148.0

(84)

84.8

(-2)

118.7

(37)

2213.5

(21)

Barak 574.0 (-30) 82.3

(-25)

59.4

(-47)

99.7

(-21)

54.5

(-48)

134.4

(46)

124.4

(35)

70.0

(-12)

1536.0

(-17)

Kynchiang 1884.6 (-45) 1056.1

(124)

33.4

(-91)

97.5

(-67)

38.5

(-89)

601.7

(175)

31.5

(-88)S

14-1

(-91)

3936.4

(-39)

Imphal & Others 63.5  (-89) 0

(-100)

0.0

(-100)

0.0

(-100)

0.0

(-100)

1.0

(-98)

20.0

(-50)

30.0

(-35)

804.5

(-31)

Naoch –Mangpui-

Lui-Muhuli-Karnaphuli

584.5 (-19) 152.5

(56)

56.7

(-41)

27.9

(-64)

80.0

(-9)

84.4

(20)

 

83.8

(21)

72.3

(-12)

1322.5

(-16)

EAST FLOWING RIVERS GANGA TO GODAVARI Mahanadi 335.5 (-16) 58.9

(-19)

70.8

(-17)

139.9

(65)

28.4

(-63)

86.6

(41)

72.5

(1)

31.2

(-18)

1027.8

(-7)

Subernrekha 362.8 (-1) 75.5

(12)

81.3

(-1)

98.1

(12)

108.4

(64)

136.5

(85)

50.9

(-27)

13.7

(-68)

1084.1

()

Brahmani &  Baitarni 377.8

(-9)

73.5

(-5)

72.7

(-5)

88.1

(-3)

76.7

(7)

72.7

(8)

64.4

(-4)

28.6

(-36)

1063.9

(-7)

Vamasdhara (10830 sq km) 284.4 (-2) 49.9

(-13)

39.9

(-29)

62.0

(29)

16.4

(-70)

41.7

(-13)

40.1

(-22)

34.9

(-37)

765.1

(-8)

Nagvali (9510 sq km) 293.9 (21) 78.2

(69)

52.6

(28)

18.7

(-49)

11.7

(-74)

37.4

(-12)

59.3

(33)

73.8

(45)

839.3

(19)

Godavari Upper 308.3 (32) 40.7

(0)

89.9

(111)

28.4

(-25)

0.2

(-99)

22.7

(-37)

3.2

(-91)

81.1 (220) 671.7

(10)

Middle 352.3 (33) 79.1

(48)

89.2

(58)

16.4

(-62)

3.6

(-93)

39.1

(-18)

26.3

(-20)

93.3

(190)

948.9

(30)

Lower 471.8 (41) 80.3

(9)

69.5

(-1)

59.9

(-16)

10.0

(-83)

97.4

(85)

53.3

(16)

46.8

(7)

1121.0

(19)

Weinganga 524.3 (28) 81.1

(-1)

82.3

(-10)

78.5

(-19)

11.5

(-85)

14.1

(-81)

94.3

(66)

24.5

(-25)

1119.1

(-1)

Wardha 487.7 (47) 81.5

(26)

83.7

(24)

28.3

(-58)

8.2

(-86)

24.7

(-56)

38.6

(13)

47.0

(62)

947.2

(10)

Manjira 261.5 (0) 85.5

(46)

105.2 (93) 15.3

(-65)

3.3

(-94)

34.7

(-17)

69.4

(84)

123.1

(192)

985.0

(33)

Parnhita 409.1 (20) 99.6

(26)

78.9

(10)

38.6

(-42)

5.2

(-91)

28.8

(-45)

70.5

(108)

57.9

(55)

1090.0

(19)

Indravati 628.3 (42) 80.7

(-22)

108.3

(4)

161.8

(50)

10.8

(-87)

68.0

(-7)

126.2

(91)

44.2

(1)

1506.2

(19)

Krishna Upper Bhima 378.8 (40) 32.1

(-30)

102.6

(110)

125.1

(216)

17.4

(-48)

4.9

(-86)

11.0

(-67)

91.2

(127)

876.6

(27)

Lower Bhima 172.3 (-12) 124.5

(149)

68.5

(49)

7.4

(-74)

2.1

(-94)

9.4

(-74)

44.3

(23)

97.6

(107)

683.4

(13)

Upper Krishna 460.4

(33)

45.2

(-31)

97.8

(55)

138.1

(158)

23.1

(-37)

3.7

(-87)

8.4

(-64)

50.1

(36)

912.0

(14)

Middle

Krishna

[vi] 10.2

(-64)

8.0

(-76)

17.6

(-32)

54.2

(74)

67.8

(93)

670.8

(28)

Lower Krishna 261.1 (19) 46.9

(-11)

40.6

(-10)

8.3

(-77)

2.9

(-93)

31.0

(-12)

58.3

(71)

76.1

(112)

819.7

(27)

Lower Tungabhadra 152.6 (50) 23.9

(21)

46.4

(140)

2.6

(-85)

2.1

(-89)

6.1

(-62)

12.5

(-35)

38.6

(-5)

334.7

(-2)

EAST FLOWING RIVERS SOUTH OF KRISHNA BW Krishna Godavari 413.9 (65) 60.6

(-2)

55.1

(13)

6.1

(-87)

4.2

(-91)

52.4

(36)

6.9

(-80)

96.0

(170)

956.7

(33)

BW Krishna

Pennar

130.8 (1) 12.6

(-57)

18.6

(-26)

1.8

(-90)

0.0

(-100)

21.3

(-8)

78.0

(248)

25.4

(-16)

408.1

(-1)

Pennar 164.3 (41) 33.5

(32)

67.6

(213)

0.3

(-99)

0.3

(-99)

10.7

(-52)

12.9

(-58)

44.2

(7)

425.7

(9)

Ponnaiyar-Palar 154.1 (34) 49.8

(84)

36.7

(73)

1.9

(-92)

8.1

(-74)

17.0

(-36)

12.9

(-58)

28.1

(-36)

388.2

(-10)

Cauvery 157.8 (-17) 28.6

(-18)

34.1 (19) 9.8

(-64)

12.1

(-59)

14.3

(-33)

6.2

(-75)

5.7

(-85)

341.5

(-31)

Vaippar-Parniba 51.7  (-13) 17.9

(43)

9.7

(11)

2.4

(-78)

10.4

(-30)

32.0

(149)

3.5

(-80)

4.6

(-78)

186.9

(-15)

WEST FLOWING RIVERS Luni

Saraswati

Bhadar

131.8 (-36) 11.3

(-73)

77.4

(96)

144.4

(259)

36.3

(19)

12.0

(-61)

2.2

(-92)

45.0

(325)

546.6

(6)

Sabarmati 154.7 (-40) 13.6

(-74)

60.0

(-2)

107.8

(82)

44.1

(1)

20.1

(-62)

1.8

(-95)

20.4

(20)

622.8

(-13)

Mahi 294.2 (13) 30.3

(-52)

101.5

(53)

151.1

(120)

151.8

(165)

29.0

(-49)

1.5

(-96)

28.9

(38)

898.5

(14)

Narmada 438.7 (29) 36.6

(-53)

109.0

(28)

111.7

(23)

61.2

(-11)

32.1

(-53)

4.1

(-92)

75.7

(107)

1000.8

(-2)

Tapi 321.2 (13) 35.6

(-36)

64.6

(15)

56.8

(-6)

10.8

(-73)

23.2

(-47)

5.1

(-84)

80..3

(243)

699.9

(-4)

WF South of Tapi 1092.7 (-6) 164.0

(-15)

214.1

(19)

168.9

(17)

68.3

(-40)

32.2

(-63)

29.8

(-50)

122.6

(138)

2116.9

(-10)

Highlights A closer look at the table and the map provides some highlights:

  • Out of 59 basins, 6 have deficient rainfall, 10 have access rainfall and 41 have normal rainfall (no data for 2).
  • Highest normal rainfall monsoon is for Kynchiang basin in Meghayala, with 6473.4 mm nornmal rainfall. The only other basin with more 2000 mm normal rainfall is the composite basin of West flowing rivers south of Tapi, with normal rainfall of 2358.1 mm.
  • Lowest normal monsoon rainfall, is not in case of Rajasthan, Kutch, North Karnataka or Rayalseema basin, but is for Vaippar in South Tamil Nadu with normal SW Monsoon rainfall of only 218.8 mm, but this basin would get benefit of rainfall also in North East Monsoon. Lower Tungabhadra with normal SW Monsoon rainfall of 342 mm is the second lowest one.
  • The highest surplus rainfall % was registered in Tons basin in Madhya Pradesh, at 51% above normal rainfall. The highest deficit was recorded in Kynchiang basin with deficit of 39%.
  • In the table above we have highlighted relatively high deficits (pink) and relatively high surplus rainfall (blue).

Limitations There a number of limitations as of now. The data is still not available for some of the basins (e.g. Jhelum and Upper Indus Basins) and is also not available regularly (weekly maps were missing for several weeks). Also the maps are not archived, so if you missed map of specific day, week or season rainfall map till a specific week, it is not available on the website. The maps are also not downloadable, so all you can do it save screenshots. As we pointed out to some IMD friends, one can sometimes see discrepancies when we compare state-wise/ Meteorological division wise and river-basin wise data for a specific date, they seem to give misleading picture if the rainfall is normal, deficit, scarce or surplus in a river basin.

We hope IMD will take necessary steps to remove these limitations and improve the availability and access of basin wise rainfall maps and data in coming years. 

Bhim Singh Rawat and Himanshu Thakkar (ht.sandrp@gmail.com), SANDRP

END NOTES:

[i] See http://hydro.imd.gov.in/hydrometweb/(S(34dugmrmvepqd355maecep55))/landing.aspx

[ii] This column gives rainfall figures from June 1, 2016 to July 19, 2016.

[iii] The figures in this column are based on calculations from other maps.

[iv] Total Rainfall figures from June 1 to Sept 30, 2016.

[v] No rainfall figures are given for Upper Indus and Jhelum basins. The rainfall figures for Beas basin are also not given separately.

[vi] Data of rainfall for some of these periods were not given on IMD website.

7 Comments on “Welcome development: River basin wise rainfall maps from IMD!

  1. It would be better if the river lines are given in the back ground. There is no provision to view bigger size map and it is clumsy. The Tungabhadra river basin is shown as two parts but data is available for only one. It needs lot of improvements and through check up. The location of rain gauging stations falling in each sub basin to be given in the IMD web site.

    Liked by 2 people

  2. Thanks for this. One additional limitation is that IMD has not put out information on how the basin level rainfall is calculated and how it varies within the basin. They need to show the rainguages used, the method used for interpolation (e.g., Theissen polygon), and ideally of course should give the gauge-wise data also.

    Liked by 1 person

    • Yes, Sharad, Totally agree. I had this in mind, but did not mention since I thought this is asking for too much when there are so many primary limitations. In fact they have not even given the area of each sub basin and logic of the divisions.

      Like

  3. It is not necessary to make a screenshot. I was able to get the URL for a high-resolution river-basin-rainfall map. Contact me if you need help doing that. Mobile: nine-845222813 (first digit spelled out to avoid spam). Email: tomelam at gmail.com.

    Liked by 1 person

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