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Rainwater Harvesting System (RHS)

Rainwater Harvesting System (RHS) . Jean Pierre Nshimyimana , SM Civil and Environmental Engineering, MIT 2010. System Overview . Technical Analysis . Rainfall data Estimate the water demand and the storage capacity Comparison : Rainwater collected and water demand

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Rainwater Harvesting System (RHS)

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  1. Rainwater Harvesting System(RHS) Jean Pierre Nshimyimana , SM Civil and Environmental Engineering, MIT 2010

  2. System Overview

  3. Technical Analysis • Rainfall data • Estimate the water demand and the storage capacity • Comparison : Rainwater collected and water demand • Identify other water sources in the area

  4. Technical Analysis: Technical Feasibility ARWS: Annual Roof Water Supply RA: Roof Area AR: Annual Rainfall: Total of monthly averages RC: Roof Coefficient (depending on the material of the collection surface e.g. roof covered in iron sheets has a coefficient of 0.9) Decision on technical feasibility: Feasible RHS: ARWS > Estimated Water Demand RHS to be supported by another water source: ARWS> Water Demand or ARWS = Water Demand

  5. Economical & Social analysis Economical Analysis Social Analysis Acceptability of the test of rainwater by the local population Community understandings of the RHS use Evaluate community needs for RHS (based on water demand) Compare RHS accessibility to other local water sources in the areas • Cost estimation & cost return analysis • Available material at the local market • Sustainability of the material to be used ( learning from local preferences) • Materials durability versus cost • Learn From locally built RHS

  6. Estimating the Size of the Storage Unit Sizing Factors: • Rainfall data and Seasonality • Area of water collection (roof area) • Runoff coefficient (0.5 - 0.9 determined by the roof material) • Water Demand (users & consumption rates )

  7. Estimating the Size of the Storage Unit Method 1: Demand Side Approach Size of the Reservoir: DC (Daily Consumption) x LDP (Long Dry Period in days)x number of people supplied Example: 1.Consumption per capita per day, C = 20L 2.Number of people per household, n = 6 3.Longest average dry period = 30 days • Annual consumption = C x n*365 = 43,800L RHS Storage Size, T = (43,800 *30)/365 = 3,600L Or Storage, T= 20*6*30=3,600L Source: http://www2.warwick.ac.uk/fac/sci/eng/research/civil/dtu/rwh/sizing/

  8. Size of the Reservoir Method 2: Supply Side Approach

  9. Estimating the Size of the Storage Unit Resources: http://www2.warwick.ac.uk/fac/sci/eng/research/civil/dtu/rwh/sizing/ Performance: http://www2.warwick.ac.uk/fac/sci/eng/research/civil/dtu/pubs/rn/rwh/rnrwh04/ http://www2.warwick.ac.uk/fac/sci/eng/research/civil/dtu/rwh/model/input_data/

  10. Practical Considerations Type of Roofs Not appropriate for a durable RHS

  11. Guttering :

  12. Reduce Debris Loading from the Roof During installations in developing countries we can use chicken wire mesh or Sand mesh (http://www.alibaba.com/showroom/sand-filter-mesh.html) http://www.fasciadivision.co.uk/images/rainwater-guttering.jpg, http://www.mdguttershutter.com/images/gutters.jpg

  13. Local Guttering Options: Collecting rainwater from a thatch roof Gutter holder used for hail control under tropical climate Locally made guttering system Example of hailing condition : Rwanda

  14. Tools: Guttering and Piping http://www.wickes.co.uk/content/ebiz/wickes/resources/images/goodIdeaLeaflet/wickes-gutters-fig1.jpg

  15. http://www.wickes.co.uk/content/ebiz/wickes/resources/images/goodIdeaLeaflet/wickes-gutters-fig1.jpghttp://www.wickes.co.uk/content/ebiz/wickes/resources/images/goodIdeaLeaflet/wickes-gutters-fig1.jpg

  16. Local Storage Options:

  17. Installation of Storage Unit Stand for the storage unity Fence option for large system

  18. Storage: http://www.spec-net.com.au/press/1208/images/yan101208_img01.jpg

  19. Rainwater Purification • To select a rainwater purification option, you have to consider: • End use of rainwater collected, • Water purification method used locally, • Availability of local material that can be used to build a filter e.g. sand, ceramic material • Cost and accessibility of filter cartilages in • Case an advanced filtration method can be affordable Sand filter Use of gravel

  20. Suggestions for Group Estimations before the field work of January : • Estimate the water demand for your project • Compare the Water demand to the annual rainwater supply of your case (technical feasibility) • Decided if RHS is feasible for your project? Find alternative water sources if the latter is not enough for the estimated water demand • Estimate size of the storage unit • Put together a list of materials needed for your RHS project and contact the local community for the availability of material needed at local level • Work with the community partner to put together a social and economic analysis for your project (cost effectiveness of the project and acceptability of rainwater as a water sources) • Probable Challenges projected during the implementation phase and brainstorm affordable solutions • Check the following site for additional material on the project I implemented in Rwanda http://www.clinicsrising.com/documents/water-sanitation/

  21. For questions and suggestions: Jean Pierre Nshimyimana njepiealm@alum.mit.edu

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