Demand for Water - Let’s start with the 736 people, in two different villages, each with its own rainwater catchment (RWC) tank. For simplicity, let’s say that each village has an average population of 368 people. At 30 liters per capita per day, that’s a daily demand of 11,000 liters. If each tank stores half a day...
Demand for Water - Let’s start with the 736 people, in two different villages, each with its own rainwater catchment (RWC) tank. For simplicity, let’s say that each village has an average population of 368 people. At 30 liters per capita per day, that’s a daily demand of 11,000 liters. If each tank stores half a day’s consumption, then each tank has to have a capacity of about 5.5 cubic meters.
System Design
Tank Choice - You have a choice between a brick, ferrocement, or steel tank. Steel is easiest, but probably most expensive. Ferrocement is more difficult to build, but cheaper than a steel tank. Brick is relatively easy to build, but probably heavier than the ferrocement or steel tank. The quality of the constructed tanks (ferrocement or brick) depends upon the skills of the local builders.
Water Source – the main focus of your plan (and its title) refers to rainwater catchment. I don’t know of any place where rainfall is sufficient to provide enough water to a community on a year around basis. There almost always has to be some supplemental system. In your case, you briefly mention the hand pumps. According to one internet source: “From October to March, during the period of low sun, the weather is generally dry with many fine, hot, sunny days. The season of high sun, from April to September, is the rainy season. The rainfall increases to a peak in July and August and then decreases until rain has almost ceased by November.â€Â
Layout – You need a better description (a drawing would help) of the proposed system. I don’t understand what you mean by the idea to: “create one tank in each village, enlarge the top platform and create a roof on top of this platform. So the communities have a RWHT as well as a community centre. No problems will occur because the tank uses a roof of a private house and the community has a place to gather.†What’s a RWHT? Presumably the “RWT†is for rain water tankâ€Â. What’s the “H†– “holdingâ€Â?
Second, I don’t understand from the description that you intend to “create one tank in each village and enlarge the top platform and create a roof on top of this platform†whether the water tank is on the ground or on top of the community center. I realize that the title of the project is “Creation of two rainwater tanks with community centres on top of them.†If you are going to use hand pumps, you should mention that in the title.
If the storage tank is indeed on the bottom (i.e., bottom of the tank at ground level) then you would lose the possibility of having much distribution capability, if you wanted to pipe water to another part of the village and use a public standpipe there. However, the advantage of a ground-based tank is that you wouldn’t have to build the required strong base for the tank if it were overhead.
If could have the tank on the roof of the community center, but you would need a very sound structure for the community center roof, so that the tank would not collapse the roof. Water weighs 1 kg per liter, and that means that you will have 5,500 kg of water sitting on top of the community center. You would not want to have a community center underneath it, unless you have enough money to build a very sturdy roof. For example, I would be very surprised if the school roof would be strong enough to support a 5.5 m3 tank. If I had a private house that was already built, I would not assume that it had the capability of supporting a water tank weighing 5,500 kg. You need to present a much clearer description of the design you are considering, and a realistic cost estimate for the support structure for the proposed water tank.
Operation and Maintenance - Who is going to be responsible to keep the tank filled using the hand pumps? Will they get paid? If so, who will pay them? Are pump parts readily available locally when the pump needs fixing? You should check out the recommendations of the huge effort that the World Bank put into a world-wide hand pump program back in the early 80’s to see what the lessons learned were. Lack of convenient access to parts was a major problem.
Financing and O&M – Even hand pumps break down eventually. Who will buy the spare parts, and where will they buy them? Are there local pump distributors who can provide parts on short notice? Are people willing to pay some small amount for a skilled worked to take care of the water pump and tank? Is le 200 enough to cover the pumper(s) wages, and spare parts for the hand pumps? I’m not sure about the proposed costs, as it would largely be driven by the choice of what type of tank to use, and how much they cost locally. Therefore, I cannot comment in any detail on the proposed pricing.
However, I do have one concern that was mentioned by another reviewer, that being the VERY high cost per capita of the proposed system. You are proposing a project cost of $34,560 for the two tanks, two hand pumps, some shallow hand dug wells, and two modest community centers. Your cost structure does not allow me to separate out the water system cost from that of the community structures. I’ll guess that the community centers are about 25% of the overall cost (you need a more detailed cost breakdown in your revised proposal). That leaves about $26,000 for the water systems. Serving only 736 people, that’s a per capita cost of $35. Most places, assuming that you had a reasonably easily available groundwater source, you could build a decent piped water system for $25 per person. Thus, you cost estimate seems unreasonably high for the level of service you are proposing.
Water Treatment - Why do you want to chlorinate rainwater? That is usually not required, unless it is left in the storage tank so long that it begins to grow things. Are you expecting a significant bird problem or some other potential source of contamination?