Rainwater Harvesting Xiem Vn


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Regional Conference for Southeast Asia on Rainwater Harvesting in IWRM: An ExChange of Policies and Learnings

November 25-26, 2008
Davao City

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Rainwater Harvesting Xiem Vn

  2. 2. General view and purpose <ul><li>General view </li></ul><ul><li>Rainfall is distributed differently by seasons and regions </li></ul><ul><li>About 70% of slope and desertification area are not irrigated </li></ul><ul><li>More than 50 ethnic minority communities living in mountainous area </li></ul><ul><li>Water quality is big issue due to hydro-power building, urbanization and industrialization </li></ul><ul><li>Purpose of RWH technology studied </li></ul><ul><li>Cheap, </li></ul><ul><li>Easy (making, operation and management) </li></ul><ul><li>Using local materials </li></ul>
  3. 3. The research areas <ul><li>Mountainous area </li></ul><ul><li>in the Northern </li></ul><ul><li>Desert area at North </li></ul><ul><li>and South of the Middle VN </li></ul>
  4. 4. Traditional method of rainwater harvesting (RWH) in VN <ul><li>In the past </li></ul><ul><ul><li>Using roof and tree to harvest rainwater and store to the jar and tank for household water demand for rural areas </li></ul></ul><ul><ul><li>Terraced field in slope areas </li></ul></ul><ul><li>In present </li></ul><ul><ul><li>Plastic, composite, brick, rock masonry, and reinforce concrete tank to store harvesting rainwater in rainy for dry season for household demand; </li></ul></ul><ul><ul><li>Small storage lined by plastic for irrigation, </li></ul></ul><ul><ul><li>Reinforce concrete storage built in high rocky mountain for water supply and irrigation. </li></ul></ul>
  5. 6. Methodology <ul><li>Classification of RWH: </li></ul><ul><li>(by FAO and WB) </li></ul>WATER HARVESTING Surface WH (from stream) RWH At the surface of ground With physical work (run in to tank, pond, reservoir) With physical work W/O physical work Agricultural cultivation Agricultural cultivation At the roof and tree Drinking water W/O physical work (run in to the ground) Agricultural cultivation Drinking water Drinking water With physical work Source for harvesting By kind storage By purpose of use
  6. 7. With Physical work: <ul><li>Brick masonry pond, tank </li></ul><ul><li>Pond lined by clay </li></ul><ul><li>Pond lined by composit layer for </li></ul><ul><li>infiltration block </li></ul><ul><li>... </li></ul>
  7. 8. Method ology for design calculation for RWH system <ul><li>Without physical work: </li></ul><ul><li>Water balance equation: </li></ul><ul><li>SWi + R + U – E – T – D = SWi+1 </li></ul><ul><li>Where: </li></ul><ul><ul><li>SWi, SWi+1: the depth of aquifer at root-depth for time (i) and (i+1) </li></ul></ul><ul><ul><li>R: rainfall </li></ul></ul><ul><ul><li>U: runoff created by area A </li></ul></ul><ul><ul><li>E: evaporation at the cultivated area a </li></ul></ul><ul><ul><li>T: tree evaporation </li></ul></ul><ul><ul><li>D: infiltration </li></ul></ul><ul><ul><li>Z: effective root depth </li></ul></ul>Z: Chiều sâu hiệu quả tầng rễ Aquifer with root depth
  8. 9. Method ology for design calculation for RWH system (cont.) <ul><li>With physical work: </li></ul><ul><li>- Determination of water storage volume V: </li></ul><ul><li>V = (W 0 .* M - Wa) + Wt (m 3 ) </li></ul><ul><li>where : </li></ul><ul><ul><li>W 0 (m 3 /ha): water demand of specific tree; </li></ul></ul><ul><ul><li>M (ha): cultivated area; </li></ul></ul><ul><ul><li>Wa (m 3 ) : volume of water from other sources </li></ul></ul><ul><ul><li>Wt ( m 3 ): safety storage volume </li></ul></ul><ul><li>- Determination of catchment A: </li></ul><ul><li>A = V/(C x R) (m 2 ) </li></ul><ul><li>where: </li></ul><ul><ul><li>V: water storage volume (m 3 ); </li></ul></ul><ul><ul><li>R: design annual rainfall (m); </li></ul></ul><ul><ul><li>C: RWH effective coefficient. </li></ul></ul>A V M
  9. 10. Basic data for RWH system design <ul><li>Rainfall </li></ul><ul><li>Water resources </li></ul><ul><li>Temperature, huminity, evaporation, wind </li></ul><ul><li>Topography </li></ul><ul><li>Soil </li></ul><ul><li>Type of tree and its cultivation measure </li></ul><ul><li>Economic efficiency </li></ul>
  10. 11. Rainwater harvesting for slope area (in the mountainous area, north Viet Nam Harvesting Storing Irrigating Cross section Plan <ul><li>Gutters </li></ul><ul><li>Ditch take water from gutters </li></ul><ul><li>Deposition and filtration pool </li></ul><ul><li>Pipe </li></ul><ul><li>Storage </li></ul>1 3 Slope 2 4 5
  11. 12. Rainwater harvesting for desert area (in south-middle Viet Nam with annual rainfall is 500-700mm) HDPE 0.3mm for RWH catchment Pipe system Pond Fruit - tree crop Neem tree for wind barricade Fruit tree Neem tree for wind barricade
  12. 13. Material selection and structural calculation <ul><li>Experiment in the Lab and field to identify suitable materials: </li></ul><ul><li>HDPE film, </li></ul><ul><li>Concrete mixed by soil and cement </li></ul><ul><li>Thin reinforce concrete </li></ul><ul><li>Brick masonry </li></ul><ul><li>Structural calculation based on selected material and shape for storage optimization with cost and stable </li></ul>
  13. 14. Basic design for tank by materials
  14. 15. Basic design for pond and catchment Catchment and pond Gutter B b d m=1-1,5 m=1 m=1 h i
  15. 16. Basic design for inlet
  16. 17. Pilot project: <ul><li>1. In Cao Phong – Hoa Binh province </li></ul><ul><li>- Slope: 10% - 20%. </li></ul><ul><li>Average annual rainfall: 2114 mm, rainy season (May - Nov) = 80% annual rainfall </li></ul><ul><li>Other water resources: no </li></ul><ul><li>Tree: orange and sugar-cane </li></ul><ul><li>Cultivated area: 1000 ha </li></ul>
  17. 18. Planning for 1000ha
  18. 21. Result of model Efficiency coefficient of RWH system vs 10days rainfall
  19. 22. Result of model <ul><li>- High efficiency of storage: 93%; </li></ul><ul><li>90% sediment have been blocked by deposition and filtration system; </li></ul><ul><li>85% cultivated area irrigated by gravity; </li></ul><ul><li>- High declining of soil erosion </li></ul>
  20. 23. Result of model <ul><li>Local people can build and easy for operation and maintenance </li></ul><ul><li>Meet water demand of tree during the year </li></ul>
  21. 24. Result of model <ul><li>- Orange in the project area is taller than outside by 20 - 30%. </li></ul><ul><li>- Economic analysis: </li></ul><ul><ul><li>Cost is 10 -14 USD/1m 3 storage decreased by 4-5 times comparison with reinforce concrete and rock masonry </li></ul></ul><ul><ul><li>B/C (12%)= 3,25 </li></ul></ul><ul><ul><li>EIRR= 33,2% </li></ul></ul>
  22. 25. Pilot project (cont.) <ul><li>2. In Bac Binh – Binh Thuan province </li></ul><ul><li>- Slope: 5% - 10%. </li></ul><ul><li>Average annual rainfall: 700 mm, rainy season (Jun - Oct) = 85% annual rainfall </li></ul><ul><li>Baking sun, high evaporation, high wind speech; </li></ul><ul><li>Other water resources: no; </li></ul><ul><li>Soil: sand dune, desetification; </li></ul><ul><li>Tree: medical tree (local called neem) </li></ul><ul><li>Project area: 4ha </li></ul>
  23. 26. Planning for 4 ha Neem tree Trôm tree RWH system
  24. 27. Result <ul><li>High efficiency of harvesting (>70%); </li></ul><ul><li>Efficiency of storage is high with good coverage water lost by <10%. </li></ul>
  25. 28. Result <ul><li>Plant is growing well; </li></ul><ul><li>Economic analysis: EIRR= 22,8%; </li></ul><ul><li>New project has been implementing with 100 ha; </li></ul>
  26. 29. Some other projects applying this technology in VN <ul><li>Environmental project for desertification declining in southern of Middle Viet Nam funded by government </li></ul><ul><li>Project for desertification declining funded by GEF (UNDP) in Thanh Hoa, Nghe An provinces; </li></ul><ul><li>Rural development project in mountainous area in Binh Thuan province. </li></ul>
  27. 30. <ul><li>Thank you for attention! </li></ul>