Montana: 20k Gallon Off-Grid Rainwater for Drought Resilience
By Paul Wheaton
TL;DR: A detailed build log demonstrates how a 20,000-gallon buried cistern system can achieve 100% irrigation self-reliance for permaculture.
- Large-scale rainwater capture ensures drought resilience.
- Careful planning of cisterns, pumps, and distribution is key.
- Automation enhances efficiency and water quality.
- Detailed documentation supports replication and maintenance.
- Open-source designs foster community adaptation.
Why it matters: Implementing robust off-grid water systems can secure food production against unreliable rainfall and changing climates, fostering true self-sufficiency for permaculture sites.
Do this next: Calculate potential rainwater harvest for your property using your roof area and local rainfall data.
Recommended for: Experienced permaculturists, homesteaders, and community leaders looking to implement robust, self-sufficient water infrastructure.
Paul Wheaton's Permies forum build log chronicles a 20,000-gallon (75,700L) buried cistern system for Montana permaculture, achieving 100% irrigation self-reliance over 5 years of droughts. Roof catchment from 5,000 sq ft (465m²) corrugated metal yields 0.9L/m²/mm, captured via 150mm PVC downpipes. Automated first-flush uses Arduino-controlled solenoids diverting 50L at 8L/min, programmed for rainfall intensity via tipping bucket sensors. Cistern construction: excavated pit lined with bentonite clay, HDPE liner, and concrete cap, pressurized tested to 2psi. Pump sizing details a 1HP submersible (40L/min at 30m head) with VFD for variable speed, gravity backup via 10m elevation siphon. Distribution pipes 50mm HDPE to zones, with pressure compensating drippers (2L/h). Five-year results: 180,000L annual yield from 350mm rain, supporting 2ha food forest. CAD files include AutoCAD DWGs for diverter, tank, and plumbing; material lists total $12,000 (e.g., $5k cistern, $2k automation). Maintenance logs cover sensor calibrations and winter antifreeze loops. Forum discussions add user mods like solar integration. Replicable for off-grid sites, with yield calculators and troubleshooting (e.g., vortex inlets prevent sediment).