Water resources in the coastal zone of Bangladesh: constraints or opportunities for cropping...
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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
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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
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• 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?
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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
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• 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
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• 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 at Gorai intake after dredging
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Salinity
(ppt)
Salinity observed at Khulna during different year
Year 2012 Year 2011 Year 2010 Year 2009 Year 2007
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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
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• 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
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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
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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.
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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
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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
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Grain Yield (t/ha)
Soil salinity (av 0-‐90 cm EC 1:5 dS/m For ECe mul6ply by 10)
Salinity trial of wheat
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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
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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 |
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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