INTERNATIONAL FOOD POLICY RESEARCH INSTITUTE

The use of global databases in developing SWAT applications to Sub-Saharan Africa and South Asia for large-scale hydrological and crop simulation

Hua XiePostdoctoral Fellow

International Food Policy Research InstituteWashington D.C.August 5-7, 2009

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Agricultural Water Management Solutions

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• Identify promising investment options for smallholder irrigation in Sub-Saharan Africa and South Asia

Sub-Saharan Africa (SSA)

South Asia (SA)

Smallholder irrigation

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• Irrigation technologies for smallholders (FAO)

• A `bottom-up' or `grass-roots' approach to development , and in contrast to formally structured irrigation schemes that are usually under the control of a government body (FAO)

— Water harvesting— Swamp irrigation— River flood plain irrigation— Spate irrigation— Hill irrigation— Groundwater irrigation

Smallholder irrigation

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A field trip to Ziway, Ethiopia, May, 2009

Objectives of the SWAT modeling

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• Perform hydrologic and crop simulation to evaluate the physical potentials of smallholder irrigation in terms of crop yields and environmental impacts at a continental scale

Meteorological data base (input)

Hydrology

Erosion, nutrients

& agricultural

chemicals

Crop/plant

growth

Water & land

management

SWAT

Information flow Control flow

Setting up the SWAT applications for Sub-Saharan Africa and South Asia

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Databases

• HydroSHED — based on SRTM (Shuttle Radar Topography Mission) 90m

DEM database

• Harmonized World Soil Database v 1.1

• Global Lakes and Wetlands Database (Lehner and Döll, 2004)

• CRU (Climate Research Unit, University of East Anglia) database

• GRDC (Global Runoff Data Centre) database

• FAOSTAT

References— Schuol, J., K.C. Abbaspour, H. Yang, R. Srinivasan, and A.J.B. Zehnder

(2008), Modeling blue and green water availability in Africa, Water Resources Research, 44: 1-18

— WaterBase project (www. Waterbase.org)

Challenges in setting SWAT applications for Sub-Saharan Africa and South Asia

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Elevation

• HydroSHED

SWAT GIS Interface

Delimited irrigation area

Land coverSoil

• Harmonized World Soil Database v 1.1

Lakes, wetlands and reservoirs

• Global Lakes and Wetlands Database

SWAT-SSA&SA

Model application

ClimateRunoff

Agriculture

• CRU• GRDC

• FAOSTAT

Challenges in preparing crop-specific land cover database for Sub-Saharan Africa and South Asia

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• FAOSTAT

— statistically based

— crop specific, but not spatially disaggregated

• GLC 2000 and MODIS

— satellite based

— spatially disaggregated, but not crop specific

The SPatial Allocation Model (SPAM)

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Cross-entropy method

Crop production statistics by administrative unit (from FAOSTAT)

(c) Production system structure (rainfed/irrigated, high input/low substance)(b) Cropping intensity/season(a) Crop land extent/satellite –based global land cover databases (GLC 2000 & MODIS)

(d) Biophysical suitability for crop production

(f) Existing crop distribution data sets

Grid-based estimates

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Reference: You, L. and S. Wood (2006). An entropy approach to spatial disaggregation of agricultural production. Agricultural Systems. Vol.90, Issues1-3, 329-347

(e) Crop prices

The SPatial Allocation Model (SPAM)

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Non-crop land

SPAM grid (10km×10km)

Crops1. Wheat 2. Rice3. Maize 4. Barley5. Millet 6. Sorghum7. Potato 8. Sweet potato and yams 9. Cassava 10. Plantain & banana11. Soybean 12. Beans13. Other pulse 14. Sugar cane

15. Sugar beets 16 Coffee17. Cotton 18. Other fibres

19. Ground nuts 20 Other oil crops

Rainfed & high input

Rainfed & low input

Irrigated

Area (ha), yield (ton/ha) & production (ton)

Delimit irrigation areas for SWAT modeling

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• Hydrologic Response Units (HRUs) — basic spatial units in SWAT modeling

• HRUs are defined by overlaying soil, land cover and slope data layers

• An additional layer for irrigation area delimitation is compiled to help define the HRUs where irrigation could be applied

Land cover

Soil

Slope

Irrigation

Delimit irrigation areas for SWAT modeling

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“Riparian” vs. “non-riparian” irrigation

Riparian irrigation cropland

Non-riparian irrigation cropland

Developing algorithms in SWAT modeling for simulating smallholder irrigation

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Runoff Irrigated waterStorage

Smallholder irrigation • Water Harvesting• Swamp irrigation• River flood plain irrigation• Spate irrigation• Hill irrigationFormally structured irrigationDomestic & industrial water use

(Shen & Oki et al., University of Tokyo)

Global databases for SWAT-SSA & SA applications development

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Database Sources/agencies

Topography HydroSHED WWF

Soil Harmonized World Soil Database v 1.1

FAO/IIASA/ISRIC/ISSCAS/JRC

Land cover SPAM IFPRI

Reservoirs, lakes and wetlands

Global Lakes and Wetlands Database

Lehner and Döll (2004)

Irrigation Irrigation areas delimitation data layers

IFPRI

Water withdrawal (for domestic & industrial use)

Global water withdrawal database

University of Tokyo

Climate CRU Climate Research Unit, University of East Anglia

Runoff GRDC Global Runoff Data Centre (GRDC)

Crop yields FAOSTAT FAO

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