Rain Water Harvesting Guidelines - Oxfam WASH

Key Takeaways

These guidelines provide detailed methods for effective rainwater harvesting and reservoir design tailored to community needs.

• Estimate reservoir capacity against monthly demand
• Use graphical analysis for maximum storage determination
• Design for gravity flow in distribution systems
• Factor in ecological impacts and site selection
• Establish benchmarks for community water access

Why It Matters

These guidelines enable efficient water management for communities, crucial in areas facing water scarcity. By implementing these strategies, communities can ensure sustainable access to water while considering environmental impacts.

What to Do Next

Review local rainfall data to assess your water harvesting potential.

Permaculture Context

For permaculture designers and regenerative homesteaders, the real value of Oxfam's WASH rainwater harvesting guidelines lies not in the humanitarian framing but in the underlying methodology, which transfers directly to farm-scale and community water planning. The cumulative demand versus cumulative supply graphing technique is particularly worth adopting: rather than guessing tank size based on roof area alone, it forces you to map the seasonal gap between when rain falls and when your garden, livestock, or household actually needs water most. That gap is almost always larger than intuition suggests, especially through dry summers or drought years. The gravity-flow pressure standards and the one-point-per-250-people benchmark also push designers toward thinking in terms of redundancy and shared infrastructure, principles that sit at the heart of zone and sector planning. Practically speaking, if you are sizing a storage tank, designing a swale-to-cistern system, or planning a community water share arrangement, this document gives you a replicable, field-tested framework rather than a theoretical starting point. That distinction matters enormously when water security is non-negotiable.