Daudi Makamba, WaterAid Tanzania, Kiteto programme, Tanzania,

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1 Rainwater Harvesting Techniques for Rural Houses Daudi akamba, WaterAid Tanzania, Kiteto programme, Tanzania, Abstract Kiteto District Arusha region is one of the semi arid and arid areas in Tanzania. WaterAid (UK, NGO)Tanzania, Kiteto programme has been working in this area since 997 to improve rural water supply, hygiene promotion and sanitation. WaterAid Kiteto programme is working together with local NGO known KINNAPA and Kiteto District Council (KDC) under tripartite partnership. Currently, this WaterAid /KINNAPA /KDC programme is implementing six borehole schemes. The big challenge that the programme faces is to locate the borehole sites. According to the hydrogeological studies it was noted that water is found in fault and not in sand aquifers which is very difficult to locate them. Also their recharge is minimal due to little amount of rainfall in a year (00mm 600mm). Even the cost is high compared to the rural communities income especially, when considering the issue of operation and maintenance costs. Therefore the programme started to opt to other alternative technologies for water sources such as improvement of traditional wells and harvesting rainwater. The rainwater harvesting technologies include sand dams, small dams, underground tanks and roof catchment for domestic uses. Responding to this it is planned to conduct training to the mobilization team regarding the rainwater harvesting technologies. Thus the paper wrote by the Project Engineer WaterAid Kiteto is aimed to build the capacity of the TUWI * team to disseminate Rainwater harvesting technologies particularly for roof catchment (starting with Ndaleta village)..0 Introduction The training was aimed to build the capacity of TUWI team to disseminate rainwater harvesting system technology in Ndaleta village. The village people population is approximately 950. The area experiences difficulties in existence of groundwater. Basing on these facts, The WaterAid /KINNAPA/ KDC programme decided to opt on Rainwater Harvesting System Technology at least to supplement two boreholes drilled recently. The boreholes' yields are very low ranges from..0 m /hr. Also there is an earth dam (shared with nearby village Njoro) approximately 6km away. Often the dam dry in very year during the driest period and people in this village are supposed to travel up to 5km to obtain water for domestic use. The training is mainly planned to concentrate on rainwater harvesting using tinned roofs and aasai type roofs Tembe* *..0 Advantages and Disadvantages of Rainwater Harvesting Technologies Table I: Advantages Quality of rainwater is high System is independent and therefore suitable for scattered settlements Local materials and skills can be used for construction energy costs to run the system Ease of maintenance by owner/user Convenience and accessibility of water, valuable time is saved in collecting water Disadvantages High initial costs The water available is limited by rainfall and catchment area Rainwater is mineral free (flat taste and may cause nutrition deficiencies).0 Feasibility of Rainwater Harvesting System Technology (RHST) To be determined in light of the constraints: a). Technical constraints Availability of rainwater (quantity and variability) Demand for water * Kiswahili language, means District obilization Team * * A aasai type roof or Tembe is referred as a roof covered with soil. RHST report_casec Training_Feb00 7/07/0

2 b). Economic constraints: Justification i.e cost comparison with alternatives Affordability to the users c). Social constraints: Needs of community/users Availability of skills and materials Willingness to participate and pay Generally, RHST is considered in areas where is a lack of groundwater and surface water sources..0 Design aspects. Calculating potential rainwater supply by estimating run off An estimate of the approximate, mean annual run off from a given catchment area can be obtained using the equation: S = R x A x C, Where, S ean rainwater supply in (m ), A catchment area (m ) R mean annual rainfall (mm), C run off coefficient (see table II) For instance, if R = 500mm, A = 0m, and C = 0.8 then, S = 500mm/a x 0m x 0.8 = 8000 litres per annual (8 m /annual) = litres per day. Estimating the storage tank a). Assumptions Each household has a maximum of six people (users) The minimum roof plan area is 6m, roughly measured from the roofs dimensions Per capita water demand (only for cooking and drinking demand) is 5 litres per person per day Run off coefficient = 0.8 b). Calculations Catchment area = 6 m Number of people = 6 Per capita water demand = 5 l/p/d, for drinking water only Total daily water demand = 6 x 5 = litres per day Table II onth Days in month Demand (m ) Rainfall (m) Catchment( m ) Cum. catchment January February arch April ay June July August September October vember December Total tes: Assume that no rainfall is collected during months having less than 0mm of rainfall Total catchment is less than total demand, indicating the need of another source to supplement the deficit DEAND = (Number of days in month) x (Daily water demand) RAINFALL is based on local weather station records (Kibaya weather station average of five years) CATCHENT = (Rainfall) x (Roof plan area) x (Run off coefficient) RHST report_casec Training_Feb00 7/07/0

3 CATCHENT = 0, for rainfall of less than 0mm per month The final column, cumulative catchment, assumes that rainwater collection starts at the end of dry season. Water collection starts in vember. Assuming that the whole rainfall amount is collected and there are no losses through leaks or evaporation. In the real situation, water is being taken from the tank for use at the same time as it is collected The storage volume needed to provide the maximum steady rate of water usage can be determined by drawing a line in the cumulative run off (catchment) curve representing cumulative water use (Watt, B., Ferrocement water tanks and their construction). According to the estimate roof area and total average rainfall in Kiteto the maximum tank size is.9m 5.0 Component of RHS The rainwater harvesting system includes: catchment area (roof), gutter system, storage tank, outlet and provision for disposal of first flush. 5. Known type of roofs found in Kiteto: Corrugated metal roof, thatched materials and aasai type roof (Tembe) The run off coefficient differ from one type of roof to another (see table III) Table III: Roof type Run off coefficient Corrugated metal roof (estimate) Cement tiles Clay tiles (machine made) Cement soil mix Burried plastic sheet Concrete lined Clay tiles (hand made Thatched materials aasai type roof (compacted loess soil) Source: John G and Erik N, 999, Rainwater Catchment System for Domestic Supply For the purpose of this training the techniques of collecting rainwater will consider all existing type of roofs in the referred area and the use of locally available construction materials. For the case of collecting rainwater from the aasai roofs, special techniques/ consideration will be considered. These include: a). Covering the roof by plastic sheet: Soil is topped up and compacted on the roof to increase the slope of the roof. Then, the plastic sheet is wrapped on the roof and well fixed to the roof. b). Covering the roof by Ferrocement structure: Top up soil and compact, as per part a. on the roof. Roll out (wrap) chicken wire (0 cm overlap) on top of the compacted soil. ake sure there is enough chicken wire protruded around the roof. The protruded wire will be used to cast the guttering system. Cast a sand cement mortar to cover the wire. te: When casting the mortar slightly lift up the wire to ensure that, the wire is totally covered with mortar in both sides. It should not be too runny as this would mean the mesh would not be supported and would sink through. Bend the protruded wire around the roof to the shape of gutters and then cover them by mortar. Ensure cement is well cured and covered with water and plastic sheet. c). Covering the roof with iron sheets: Top up soil and compact as per part a. on the roof. Fix the iron sheet on the compacted soil. d). Covering the roof by tiles: Top up soil and compact as per part a, on the roof. Construct/lay the tiles on top of the compacted soil/roof RHST report_casec Training_Feb00 7/07/0

4 The following are some of the issues regarding the improvement of the roof using either plastic sheet or Ferrocement structure: For the plastic sheet, it can t last very long in the sun Possible cracking after few months for the Ferrocement structure so would need to construct in joints. Possibility of sagging due to increase in weight of the topped up soil It is also noted that, by improving the roof results into problem of more smoke, this is because the roof pores are completely sealed up. These are some of the issues, which can happen if the aasai roof will be improved. Therefore, the training team is advised to be open to discuss to the community if possible to get their ideas regarding the issues. During the training the team will explain to Ndaleta people the different techniques explained in this report and demonstrate them. Then, the community will be given an opportunity to decide if there are interested with the explained techniques. 5. Guttering system for thatched and corrugated iron sheet roofs Guttering can be made from: Purpose made preformed plastic and Halfsections of pipes Galvanized steel roof sheet, cut into strips and formed into a U over a pipe or bent into a V shape Wooden planks, sealed at the joints Split bamboo 5. Storage tank The following are the general requirements of storage tank: Functional design appropriate to local conditions Water tight construction Top of the tank must be below eaves of house. aximum height of m recommended to prevent high water pressures Tank must be covered to keep out sunshine, dirt and insects Top of tank has a hole in it large enough for someone to enter the tank for cleaning or repair. The cover for this hole must be secure The overflow and entry pipes should be screened to prevent entry of flies and animals A means of removing water is needed; a tap at the bottom for an above ground tank, and a pump and pipe from an underground tank. Storage tank can be either of the following types: Traditional jars Cast concrete ring tank and Ferrocement tank Sheet metal tank Reinforced concrete tank As it was noted in section.b, it is possible to construct a tank of more than.9 m capacity. During the training a wire reinforced tank of m capacity will be considered. This is from the fact that the training is aimed to build the capacity of TUWI team to disseminate a rainwater harvesting technology in Ndaleta village. Therefore, the team will just demonstrate the construction of a medium storage tank and the guttering system. However, the training team is needed to inform the community that, according to size of their roofs and the amount of rainfall in a year for Kiteto district, it is possible to construct of more than.9m capacity. RHST report_casec Training_Feb00 7/07/0

5 6.0 Estimated training cost Item unit Qty Rate Tshs) Total(Tshs). aterial (For the training purpose) Cement Sand Gutters(Iron sheet for making them) Hessian sacks (estimate) Plastic sheet (estimate) Chicken wire (estimate) upvc pipe ( ) 6m long Double socketed elbow 90 o ( ) Iron sheet (G) m Whitewash Reinforcement bar (0 ft length) Binding wire. Tools and Equipment plasterer s steel hand floats plasterer s wooden hand floats shovels tape measure wheelbarrow for carrying mortar water containers split level hoes for excavation sieve to make sand fine (estimate) gauging box (estimate) wooden saw trowel pick axes for excavation. Construction charges (Fundi charges) Bag Ton. Bag. Kg ,000 5, ,000,000 6,500 5,000 5,000 60,000 8,000, ,000,000 8,000 6,000,000,000 5,000, day 0,000 (estimate). Contingency allowances 50,000 Total 56, Operation and aintenance (O&) The following are tasks needing particular attention: 7. Tasks needing frequent attention: Roof surfaces and gutters to be kept free of dust, organic matter and bird droppings Regular check of mosquito net on the screened pipes The inflow pipe should be disconnected in the dry season. Then 5 0 minutes after the rain begins, move connect it Check for leakage; look for cracks or wet spots on wall 7. Tasks needing infrequent tasks: Repair tank if necessary Check roof, gutters and pipes; repair if necessary If filters are used, wash or renew medium Remove deposits from the bottom of the tank After the tank has been repaired or cleaned, the interior should be scrubbed with vinegar, baking soda, chlorine bleach solution or any other local/ traditional bleach solution. 8.0 References John G and Erik N, 999, Rainwater Catchment System for Domestic Supply S. B. Watt, 978, Ferrocement Water Tanks and their Construction Jan D. and Robert L., 995, Engineering in Emergencies A Practical Guide for relief workers RHST report_casec Training_Feb00 7/07/0