effect of groundwater use on groundwater quality, piezometric level and boro rice productivity in...
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By D. Burman, K.K. Mahanta, S.K. Sarangi, Subhasis Mandal, B. Maji, U.K. Mandal, B.K. Bandyopadhyay, E. Humphreys and D.K. Sharma Revitalizing the Ganges Coastal Zone Conference 21-23 October 2014, Dhaka, Bangladesh http://waterandfood.org/ganges-conference/TRANSCRIPT
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Effect of groundwater use on groundwater quality, piezometric level and boro rice productivity in the Sundarbans of West Bengal
1D. Burman, K.K. Mahanta, S.K. Sarangi, Subhasis Mandal, B. Maji, U. K. Mandal,
B.K. Bandyopadhyay, 2E. Humphreys, and D. K. Sharma
1Central Soil Salinity Research Institute, Regional Research Station, Canning Town, West Bengal, India
2International Rice Research Institute, Los Banos, Philippines [email protected]
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Agro-climatic zones of West Bengal
Hill Zone
Terai Zone
Old Alluvial Zone
New Alluvial Zone
Red and Laterite Zone
Coastal and Saline Zone
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Indian Sundarbans and Water Challenges for Agriculture
Boro/Rabi/summer Aman/Kharif
Ø 80% fallow Ø Fresh water scarcity & salinity Ø Boro rice -3 t/ha
Ø Deep water logging & drainage congestion Ø Traditional aman - 2 t/ha
-‐10 0 10 20 30 40 50 60 70
0 2 4 6 8
10 12 14 16 18
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Water dep
th (cm)
Soil salin
ity (d
S/m)
Months Soil Salinity Water depth
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Ground water exploraUon: Farmers in the Sundarbans region are exploring ground water for growing mostly boro rice through Shallow tube wells (STWs)
Rice grown with STW irrigaUon
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Ground water scenario in Sundarbans
Fresh/saline aquifers in the coastal tract of West Bengal (Central ground water board, Govt. of India)
Aquifers :
• Mostly 70 -‐ 360 m bgl confined.
• Aquifers separated by thick clay layers
• Each aquifer system comprises one/several inter connected aquifers.
• Fresh ground water mostly in deeper aquifers
Sundarbans
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QuesUons: Is pumping groundwater for boro rice in Sundarbans sustainable?
Study: • Status of STWs • Effect of ground water use on
• water quality • piezometric level • discharge rate • producUvity of boro rice
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Study area
Surveys of STWs Period: 2000-‐01, 2002-‐03, 2008-‐09 & 2013-‐14 Districts: 2 nos. (North & South 24 Parganas) Blocks: 4 (Canning I, BasanH, Sandeshkhali I & II) Villages: 20
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(Source: Bureau of Applied Economics and StaUsUcs (BAES), Govt. of West Bengal)
~32% of irrigated area of about 55300 ha under STWS
About 2.34 ha (17.4 bigha) per STW
Depth of STWs varied from 67-‐128 m bgl 0
5
10
15
20
1994 1998 2002 2007 2012
No./ Area ( 000, ha)
Year No. Area
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Monthly rainfall & piezometric level in Dumki village during 2003
0
100
200
300
400 0
1
2
3
4
5
Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec.
Rainfall (m
m)
Piezom
etric
level (m)
Month
Rainfall STW1 STW2 STW3 STW4 STW5
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Monthly rainfall & water salinity in Dumki village during 2003
0
100
200
300
400
1
2
3
4
5
Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec.
Rainfall (m
m)
Water Salinity
(dS/m)
Month Rainfall STW1 STW2 STW3 STW4 STW5
Piezometric level & salinity restored during monsoon
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Piezometric level in STWs installed in different depths during boro season
0
1
1
2
2
3
3
4
4
5
5
<91 m (n=18) >91 m (n=26)
Piezom
etric
level ( m
bgl)
January May
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Discharge rate of STWs installed in different depths during boro season
0
2
4
6
8
10
12
14
<91 m (n=18) >91 m (n=26)
Discha
rge rate (lps)
January May
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Water salinity of STWs installed in different depths during boro season
0 1 1 2 2 3 3 4 4 5 5
<91 m (n=18) >91 m (n=26)
Water sa
linity
(dS/m)
January May
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Soil salinity developed in farmers fields during boro season due to irrigaUon through STWs installed in different depths
0
1
2
3
4
5
6
7
8
9
<91 m (n=18) >91 m (n=26)
Soil salin
ity (d
S/m)
January May
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Grain yield of boro rice irrigated through STWs installed at <91 m and >91m depths
y = 0.0387x -‐ 0.1826 R² = 0.69739
1.0
2.0
3.0
4.0
5.0
60 70 80 90 100 110 120
Boro yield (t/ha)
Depth of tubewell (m)
<91m
>91m
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Grain yield of boro rice and soil salinity irrigated through STWs installed at <91 m and >91m depths
y = -‐0.2135x + 4.7055 R² = 0.88698
0.0
1.0
2.0
3.0
4.0
5.0
0.00 2.00 4.00 6.00 8.00 10.00 12.00
Boro yield (t/ha)
Soil Salinity (dS/m)
<91m
>91m
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Conclusions " ExploitaUon of ground water in Sundarbans region of West Bengal is
increasing.
" Piezometric level & discharge rate decrease during boro.
" Groundwater salinity increases during boro season, to a greater degree in STWs at upper depth (<91m).
" Piezometric level and discharge of STWs recovered during monsoon season in Dumki village – is this the case for other areas? What happens as the extracUon of groundwater increased?
" Soil salinity increased during boro season and reduced yield up to 40 % parUcularly when irrigated with STWs at <91m depth.
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" Need for assessment of gw resources in the Sundarbans & sustainable level of extracUon across the region
RecommendaUons
rainwater harvesUng
" For increasing land and water producUvity:
" conjuncUve use of harvested rainwater & ground water (what’s the best pracUce?
" modify cropping system design e.g. early establishment of boro, switch to non-‐rice crops
" salt tolerant varieUes, shorter duraUon varieUes
" rainwater harvesUng through surface storage structures
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thank you……
Acknowledgement for the financial and technical supports to
• Indian Council of Agricultural Research
• G2: CPWF