Made from wire-mesh/ferro-cement, bricks, plastic (onion, bladder or pillow-shaped), metal sheets or clay. To capture rooftop rain or surface water. Inlet-outlet pipes, first-flush system, overflow and gutters compliment system. Popular in rural regions with water scarcity. Capacity range: ~1-30 m3.
Ferro-cement: USD26-50 per m3 storage (or USD50-100 per m3 all-inclusive installation). Brick USD20, collapsible fabric USD50-140 per m3, respectively. Plastic: USD230 for a 500-gallon tank. O&M costs are minimal. Economically sustainable if implementation is affordable by household or community.
Surface tanks optimally applied at household- or small-community level, requiring caretaker or management committee. Smaller systems may be insufficient for year-round use. Over-extraction risk during rainy season requires the drawing of a water management/utilization plan. Commercial tanks require marketing/purchase analysis.
No direct negative impact on the surrounding environment. Water storage increases climate change resilience (floods, droughts) Contaminant risk from rust (patch or paint), pathogens (chlorine treatment), BPA/PVC (filter water or use for non-drinking), rooftop material (repair or change).
Construction optimally uses community labor and resources. Prevention of contamination by filters, first-flush systems and a proper O&M plan. Cracks and corrosion repairs. Cleaning of rainwater system required before rainy season. Lifetime: plastic 25 years (or less, especially when exposed to UV), concrete 30 years, steel tanks 45 years.
Household-level: roles and responsibilities within the household are very important sustainable use. Many tanks are managed by women, since they are responsible for the management of the household and therefore also the water. Hygiene and food security benefits.
No relevant remarks for Surface-level tanks.