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By Mohammed Mainuddin, Riasat Ali, S.M. Shah-Newaz, Christian Roth Revitalizing the Ganges Coastal Zone Conference 21-23 October 2014, Dhaka, Bangladesh http://waterandfood.org/ganges-conference/
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Water resources in the coastal zone of Bangladesh: constraints or opportuni6es for cropping intensifica6on?
CSIRO LAND AND WATER FLAGSHIP
Mohammed Mainuddin, Riasat Ali, S. M. Shah-‐Newaz, Chris5an Roth November 2014
Southern Bangladesh – coastal zone
• 19 Districts, 46, 271 Km2, 31 percent of the country • About 13,000 Km2 protected by 123 polders • Popula5on – 40 million (2010) • Annual rainfall is slightly higher than the remaining area of the country • Most vulnerable to climate change
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Rainfall, mm
Coastal region
Non-‐coastal region
• Natural calami5es – cyclones, storm surge, floods, water logging, etc.
• Shortage of fresh water – both for drinking and irriga5on water
• Affected by salinity • Cropping intensity is low • Large fallow lands during Rabi –
due high salinity and lack of water
• As of 2005, 65 % popula5on are below poverty line compared to the 40% at the country level
Issues in the coastal zone
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GoB is giving importance to: • to intensify agriculture in the coastal zone • to make the zone environmentally sustainable
Key ques6ons
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The ques5ons are: Is there scope for sustainable cropping intensifica5on? What are the constraints and opportuni5es? Water resources: constraints or opportuni5es?
The main objec5ve was to iden5fy the opportuni5es and constraints to the sustainable intensifica5on of cropping systems in the coastal regions. Done in 2012-‐13
ACIAR funded scoping study
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• Complex river network-‐ 57 cross boundary rivers • Confluence of the Ganges, Brahmaputra, and Meghna Rivers • Total annual discharge is 1,200 – 1,500 billion m3 • High seasonal varia5on-‐ too much in the wet season and too lidle in the dry season • No big storage facili5es
Surface water resources
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Daily discharge at the Hardinge Bridge on the Ganges River
• Availability depends on the flow at the Ganges and the Brahmaputra
• Dry season flow at the Gorai river is very important for salinity in surface water
• Availability is decreasing due to increasing upstream use
Surface water availability – coastal zone
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Discharge of the Ganges at Hardinge Bridge
Discharge at Gorai Railway Bridge
• GoB recently spent millions to increase the flow to the Gorai river by dredging the Gorai oeake
• Dredging has increased dry season flow which reduces salinity of surface water
Surface water availability– Gorai restora6on
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Discharge, m
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Discharge at Gorai intake after dredging
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1-‐Jan 31-‐Jan 1-‐Mar 31-‐Mar 30-‐Apr 30-‐May 29-‐Jun 29-‐Jul
Salinity
(ppt)
Salinity observed at Khulna during different year
Year 2012 Year 2011 Year 2010 Year 2009 Year 2007
Considerable increase in salinity over 5me both in concentra5on and area; saline front moved further inland through the stream
Surface water salinity
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Presenta5on 5tle | Presenter name
Groundwater resources
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Aquifer systems in Khulna
Pre and post monsoon groundwater surfaces, 2010
• WL – steady or rising except some wells in in the upper part and in Noakhali
• Scope for freshwater storage in the aquifer by pumping saline groundwater?
Groundwater trend
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Noakhali Narail
Groundwater salinity
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6 m
52 m
2011 2012
• Salinity is varying in groundwater – with 5me and depth • There may be opportuni5es for limited irriga5on – but need more study.
Source: BADC
Presenta5on 5tle | Presenter name
Irriga6on – net requirements by major crops
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Average irriga5on requirements of different crops
• Net irriga5on requirement for non-‐rice crops is not very high.
• Many rabi crops can be grown with 1 or 2 strategic irriga5on.
• Scope for rabi cropping.
Salinity trial of wheat
Layout of all salinity trials: this one is Benerpota, Satkhira 28 plots deep x 4 replica6ons =112 plots: note salt on surface and adjacent lake
4 loca5ons – Satkhira, Patuakhali, Barguna, Noakhali
Grain yield of each plot against its plot salinity for the whole Satkhira site (112 plots) – Salinity measured 1 month a\er sowing
y = -‐1.6568x + 4.6653 r² = 0.10
0.0
1.0
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0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Grain Yield (t/ha)
Soil salinity (av 0-‐90 cm EC 1:5 dS/m For ECe mul6ply by 10)
Salinity trial of wheat
Constraints and opportuni6es While there are constraints of salinity and availability of freshwater for irriga5on there are opportuni5es as well. Some of these are: • Collec5on, use and management of fresh surface water, beder polder management. • Sustainable use of groundwater in conjunc5on with stored surface water for strategic irriga5on. • planning of the crop calendar to use residual moisture. • Improved agronomic management prac5ces.
Presenta5on 5tle | Presenter name 16 |
Need an integrated approach
Proposed project funded by ACIAR (2015-‐19) Cropping systems intensifica5on through integrated soil, water and crop management in the salt affected coastal zone of Southern Bangladesh and South-‐eastern West Bengal, India. • Develop regional scale understanding of the surface water and groundwater
resources. • Develop a detailed understanding of the salt and water dynamics at the
polder/sub-‐regional scale including evalua5on of groundwater resources, salt movement, surface water
• Develop detailed understanding of crop produc5on responses to various improved polder and fresh water management strategies, through experiments, field trials and crop systems modelling.
• Test suitable cropping op5ons and water and salt management through a par5cipatory approach of field evalua5on and co-‐learning.
• Pilot some up-‐scaling prac5ces for sustainable intensifica5on.
Presenta5on 5tle | Presenter name 17 |
CSIRO Land and Water Flagship Mohammed Mainuddin Senior Research Scien5st Water Resource Management Program t +61 2 6246 5929 e [email protected] w www.csiro.au
CSIRO LAND AND WATER FLAGSHIP