Changes

Natural or artificial ground catchment and Lined sub-surface tanks

No change in size, 00:02, 6 April 2012

→‎Save on costs

* Use existing soil as a natural lining if it is relatively impermeable. In China, clay has been used to line excavated water cellars (called Shuijiao) in areas where the natural soil (loess) is already fairly impermeable. The lining process is difficult and time-consuming and has been replaced largely by ferrocement or plastic. However, it proves that in some areas it is possible to construct a low-cost tank. In Somaliland, similar water cellars were observed that were excavated in impermeable stable soil formations – runoff water entered through a small inlet channel. Other tanks are sealed with a 10cm unreinforced cement lining – it seems that 30m3 is the most economical size = most volume without needing reinforcement – such tanks cost $189 or about $6.3 per m3 of storage (materials only presumably).

* In Kenya, tank linings have been made with powdered anthill material and lime which substitute some of the cement and bricks, bringing cost to $9.8 per m3 of storage.

* Reducing the size of structures. More manageable to construct in terms of cash flow, and easier to cover. This way, tanks are more affordableto families, and more tanks can be added in subsequent years, thus spreading out costs.

* However, care needs to be taken with cheap linings – in some areas with swelling clay and differential settlement, linings can easily crack, as has often been observed in some areas. The areas where cheap linings might work therefore may be site-specific, and depend on the clay content of the soil. For plastic linings, experience from India shows that these can be punctured by rodents, crabs or insects if there is no rodent/insect-proof layer before the plastic.

Winona

Akvopedia-spade, akvouser, bureaucrat, emailconfirmed, staff, susana-working-group-1, susana-working-group-10, susana-working-group-11, susana-working-group-12, susana-working-group-2, susana-working-group-3, susana-working-group-4, susana-working-group-5, susana-working-group-6, susana-working-group-7, susana-working-group-8, susana-working-group-9, susana-working-group-susana-member, administrator, widget editor

30,949

edits