COSECHA is a grassroots development organization working in southwester Honduras. One of the techniques they've developed is a ferro-cement type below ground-level cistern which we have been using extensively as part of MPP's Road to Life Yard project. MPP (Mouvement Paysan Papaye, or Farmer's Movement of Papay) where Jenny and I have been serving, also does a more traditional above-ground type of ferro-cement cistern. I'll try to describe that system in another blog.
The COSECHA-style cistern, as we generally promote it, requires the following materials:
1) A well-dug hole. We usually recommend that folks do 3 meters by 3 meters. The depth should be not much more than 1 m deep.
2) 3 lengths of 3/4" rebar. I have no idea if this is the world-wide standard, but what we purchase in Haiti and in Nicaragua are always 20' long.
3) Six to seven pounds of #18 "smooth" wire. In Haiti I've only ever seen is galvanized wire, but our teachers from COSECHA taught us with non-galvanized which is cheaper. The wire if for weaving the mesh for plastering the cement.
4) Three to four wheelbarrows of stones for the border.
5) Ten to twelve wheelbarrows of clean river sand. The sand available to families where we work in Haiti is rarely particularly clean. We do what we can with what people have available.
6) Ten to twelve bags of cement. When everything works out nicely, you can do the work with less.
7) Between seven and eight 1/4" rebar, also purchased in 20' lengths in Haiti and Nicargua. These are for making hooks that hold the rebar in place and help peg the mesh to the sides of the dirt walls.
8) At least four lengths of 4" drainage PVC for making the gutters.
9) Two 55-gallon drums of water. You may need just over one drum.
10) A medium sieve to remove pebbles from the sand.
11) A fine sieve for sifting the sand that will be used in the fine plastering of the cistern walls.
12) Shovels, picks, 18-20 liter buckets for measuring the sand and cement and carrying water, two to three cement trowels.
13) Mason-quality string for marking out the cistern and helping check levels and twelve stakes (cut from whatever tree is most common in the area).
14) A string level and a carpenter's level are helpful.
I need to go get breakfast for Keila and finish getting ready to leave the US. We head to Nicaragua tomorrow morning. I will continue to work on this blog entry to explain the pictures below. As you will note from the materials and the pictures, this is not an exact science. Folks who work with these cisterns are constantly adapting them and sometimes improving the technique. The beauty of the technique is it is easily learned and applied, and they are a very cheap and durable way to collect rainwater and they use materials that are available in most localities.