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Rainwater Harvesting (RWH) in Limpopo Basin - Challenges

CP 17 Project. Rainwater Harvesting (RWH) in Limpopo Basin - Challenges. 4 th Scientific Workshop, JHB 15 th to 18 th June 2009. Limpopo River Basin. Limpopo Basin - Rainfall. Pafuri average annual rainfall: 380.0 mm. Xai-Xai average annual rainfall: 953.0 mm.

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Rainwater Harvesting (RWH) in Limpopo Basin - Challenges

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  1. CP 17 Project Rainwater Harvesting (RWH) in Limpopo Basin - Challenges 4th Scientific Workshop, JHB 15th to 18th June 2009

  2. Limpopo River Basin

  3. Limpopo Basin - Rainfall

  4. Pafuri average annual rainfall: 380.0 mm Xai-Xai average annual rainfall: 953.0 mm Rainfall Distribution and Waterbalance

  5. Chókwè: rainfall variability

  6. Crop Failure Hazard (very high)

  7. Options in Rainfed Agriculture poverty trap what to do to reverse trends • Climate: • rainfall harvest • rainfall storage • Crops: • length • tolerance • root • Soil: • soil structure • soil management

  8. Potential for Rainfall Water Harvest

  9. conceptualization modelling Conceptual Model • Low Cost Interventions: • explore rainfall pattern; • crop (ETc); • soil storage. • Other possible interventions: • rainfall harvest and storage-supplementary irrigation; • medium to large dams and irrigation.

  10. ET crop = Kc x ETo(Kc = Kcb + Ke) • Decrease Crop Failure Hazard: • mulching to decrease soil evaporation; • increase rainfall collecting area; • soil/root water storage reservoir

  11. Rainfall Water Harvest Techniques

  12. Macro catchment Micro catchment Flood water catchment Barreira trapezoidal Barreira de pedra Represa de terra Barreira semi circular Barreira semi circular Rainfall Water Harvest Techniques

  13. Rainfall Water Harvest Techniques

  14. Rainfall Water Harvest Techniques

  15. Rainfall Water Harvest Techniques

  16. Computer Models to Assess Potential RWH • Visual Water Balance Processes for In-Field RainWater Harvesting – VISWBP-IRWH)- animation program to explain farmers and extension officers • CROPWAT model • SWAT model • PARCHED THIRST (PT) - process-based model, which combines the simulation of hydrology with growth and yield of a crop. Decision support tool that addresses challenges of low and unreliable crop production in semi arid areas

  17. Limitations of some computer Models for RWH

  18. Rainwater Harvesting (RWH) in Limpopo basin - Challenges UEM-FAEF-SUTA

  19. conceptualization modelling Conceptual Model • Crop growth model: water and soil fertility issues • Integrated Pest Management • Economical aspects

  20. Economical Feasibility of RWH Technology • Comparison of the performance of good RWH for maize, paddy and vegetable enterprises over a period of 5 years Source: Hatibuet al (2004)

  21. Rainfall Water Harvest Techniques • Plastic-covered ridge and furrow rainfall harvesting for corn production *Except labor cost Source: Yan Li et al (2001)

  22. Remarks • Adoption of RWH improve the yields and reduce crop failure. • Economic benefits of RWH are greater when coupled with high value crops associated to other agricultural inputs (fertilizers, IPM). • Successful water harvesting projects are often based on farmers’ experience and trial and error rather than on scientifically well established techniques. There are still big challenges in hydrological and crop modelling associated to economical analysis in different environments.

  23. Remarks • Although RWH can increase the water availability, the climatic risks still existing. • Planting dates are crucial, but should be based in rainfall events and other factors (soil, pests) versus risk management (e.g. two consecutive rainy days totalizing 35 mm and planting several periods in a year).

  24. CP 17 Project Thank you Rainwater Harvesting (RWH) in Limpopo basin - Challenges 4th Scientific Workshop, JHB 15th to 18th June 2009

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