1. Developing a Moderate Resolution Irrigated Area Map for
South Asia using segmentation and time series analysis
Photo: David Brazier/IWMI
Water for a food-secure world
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2. Why Irrigated Area Mapping?
• Perspective of achieving food security by
increasing irrigation
• Though 70-85 % of water used
• Especially with current situation of
population, urbanization , climate change
etc.
• Important to assess the spatial distribution,
intensity, water use etc.
Water for a food-secure world
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3. Is it new?
• Many products available globally - FAO, IWMI
• Also national products- CBIP, India
• Global Irrigated Area Map(GIAM) –
developed by IWMI in 2006
• GIAM -Resolution of 10km and datasets from
1990 -1999, AVHRR
• Very course product with detailed
classification
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4. Global Irrigated Area Mapping
• Product from IWMI - developed using multiple global
datasets
• Different datasets were used at
– Segmentation/Localization of landscape
– Classification into different units
– Time series analysis to identify irrigation
intensity
• Nominal resolution of 10KM
• Datasets used were from 1990 – 2000
Water for a food-secure world
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5. Need/Opportunity to update GIAM
• Data available from 250m spatial resolution
• Highly capable HW/SW available for data intensive
processes
• Good temporal coverage
• Extensive change in the landscape would have
happened in 12 years
• New algorithms in image classification – „object based
image analysis‟
• Updating the irrigated area map for South East Asia
Water for a food-secure world
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6. Datasets - comparison
Dataset - GIAM Resolution Proposed Resolution Availability Role
type dataset Dataset
NDVI AVHRR 10KM MODIS 250m Free Time series
/Reflectance analysis
NDVI/Reflec SPOT 1KM IRS P6 - 56m Purchase Single date
tance AWIFS classification
into objects
DEM GTOPO 1KM SRTM 90m Free conditional
segmentation
Temperature AVHRR 10km MODIS 1KM Free conditional
segmentation
Precipitation CRU 0.5 degree WorldClim 1KM Free conditional
segmentation
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7. Updated
Level 1
Methodology
Entire processing on minimum
Mapping unit – like admin
boundaries, climatic zones etc.
Level 2
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8. Level1 – Segmentation and HR
Land cover map
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9. Optimal segmentation
• Region growing algorithm – SPRING open source
software
• Main parameters; “Similarity” and “Area”
• Objective function based on spatial auto correlation
to determine best parameters
• Optimal segmentation > good classification
• Another factor > size of the image
• Bigger the size > more mix in clustering results
• Optimal size found from trial runs 250km by 200km
Water for a food-secure world
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10. Image classification steps
Original Image
Segmented Image
ISOCLASS Classified
Image
Recoded Image
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11. Level 2 – Time series on MODIS
250m NDVI
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12. MODIS Path/row for South Asia
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13. Class – flow diagram
Agriculture
Irrigated Rain fed Water source
Surface water Ground water Conjunctive Irrigation type
Continuous
Single crop Double crop From MODIS
crop
Irrigation intensity
Example class:
Irrigated, surface water, double crop
Water for a food-secure world
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14. Irrigated area calculated
Country Irrigated Area (million ha)
Nepal 4
Pakistan 21
Sri Lanka 1.6
India 169
Bhutan 0.2
Bangladesh 10
Total irrigated area calculated for entire South Asia is
206.74 million hectares.
Water for a food-secure world
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15. India
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16. Pakistan
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17. Sri Lanka
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18. Nepal
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19. Bangladesh
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20. Bhutan
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21. Speeding up the localized approach
• Use of customizable open source tools
• Developing a R package to manage the segmentation
• Program in R to control
• Dicing the imageries
• Segmentation – SPRING software
• Classification
• Extracting the agc
• Time series on agc
• Localizing based on secondary datasets
• Class assignment based on irrigation intensity
• Time consuming/Manual
• Class assignment at both classification levels
• Comments?
Water for a food-secure world
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22. Conclusions
• High resolution global datasets available now
• Introducing a localized approach to avoid mixes
• Key is to identify MMU with homogeneous pattern
• Scope for semi automating the process using R scripting
• Can‟t avoid the manual interventions though…
Water for a food-secure world
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