Sovereignty Module: Catch the Sky
Catch the Sky
Complete Rainwater Harvesting, Water Collection, and Storage Guide
Complete Rainwater Harvesting, Water Collection, and Storage Guide
Clean water is the first requirement of survival. Rainwater is the purest natural water source — free of ground contaminants, available everywhere it rains. This campaign covers collection, storage, filtration, and distribution of harvested rainwater.
Chapter 1: Rainwater Yield Calculations
| Roof Area | Annual Rainfall (inches) | Annual Yield (gallons) | Daily Average (gallons) |
|---|---|---|---|
| 500 sq ft | 20 | 6,230 | 17 |
| 500 sq ft | 40 | 12,460 | 34 |
| 1,000 sq ft | 20 | 12,460 | 34 |
| 1,000 sq ft | 40 | 24,920 | 68 |
| 1,500 sq ft | 30 | 28,050 | 77 |
| 2,000 sq ft | 30 | 37,400 | 102 |
Formula: Gallons = Roof area (sq ft) × Rainfall (inches) × 0.623. A modest 1,000 sq ft roof in a 30-inch rainfall area captures 18,690 gallons per year — enough for a family of 4 (at 12 gallons/person/day for drinking, cooking, basic hygiene).
Chapter 2: Collection System Components
| Component | Function | Material Options | Key Specification |
|---|---|---|---|
| Catchment surface (roof) | Collects rain | Metal (best), tile, slate, thatch | Smooth, non-toxic, no lead/asbestos |
| Gutters | Channel water to downspout | Half-round metal, wood, bamboo | Slope 1/16 inch per foot toward downspout |
| Downspout | Vertical pipe to storage | Metal pipe, PVC, bamboo | Sized for maximum flow rate |
| First-flush diverter | Discards first dirty water | PVC pipe (1 gallon per 100 sq ft roof) | Automatically diverts, then allows flow |
| Screen/filter | Removes leaves, debris | Wire mesh (1mm), screen cloth | At gutter entry AND before tank |
| Storage tank (cistern) | Holds water | Ferrocement, plastic, stone, wood | Opaque (prevents algae), covered, vented |
| Overflow | Handles excess water | Pipe at top of tank | Direct away from foundation |
| Tap/spigot | Draws water | Valve at bottom of tank | Slightly above tank floor (sediment settles) |
Chapter 3: Storage Tank Options
| Type | Capacity | Cost | Durability | Build Difficulty | Best For |
|---|---|---|---|---|---|
| Ferrocement (wire mesh + cement) | 500-10,000 gal | Low | 50+ years | Moderate | Permanent, large capacity |
| Plastic (IBC totes) | 275 gal each | Low-moderate | 10-20 years | Very low | Quick, modular |
| Stone/brick cistern | 500-5,000 gal | Moderate | 100+ years | High | Underground, permanent |
| Wooden barrel | 50-100 gal | Low | 5-15 years | Low | Small systems, rain barrels |
| Concrete (poured) | 1,000-50,000 gal | Moderate-high | 50+ years | High | Large permanent systems |
| Earthen (lined pit) | 500-10,000 gal | Very low | 5-20 years | Low | Irrigation, livestock |
Ferrocement tank: Wire mesh (chicken wire + rebar) formed into cylinder. Plaster with cement mortar (3-4 coats, 1-2 inches total). Waterproof interior with cement + waterproofing additive. Cheapest permanent large-capacity option.
Chapter 4: Water Purification Methods
| Method | Removes | Effectiveness | Speed | Cost | Best For |
|---|---|---|---|---|---|
| Boiling (1 minute rolling boil) | Bacteria, viruses, parasites | 99.99% pathogens | 10-20 minutes | Fuel only | Emergency, cooking water |
| Solar disinfection (SODIS) | Bacteria, viruses | 99.9% (6 hours full sun) | 6-48 hours | Free | Clear water, sunny climate |
| Slow sand filter | Bacteria, parasites, turbidity | 99% bacteria, 99.9% parasites | Continuous flow | Low (sand + gravel) | Community systems |
| Biosand filter | Same as slow sand | Same | 1-2 liters/hour | Low | Household systems |
| Ceramic filter | Bacteria, parasites, turbidity | 99.99% bacteria | 1-3 liters/hour | Low-moderate | Household drinking |
| Chlorination (bleach) | Bacteria, viruses | 99.99% | 30 minutes | Very low | Large volumes, emergency |
| Activated charcoal | Chemicals, taste, odor, some bacteria | Variable | Moderate flow | Moderate | Post-filtration polishing |
| UV light (sunlight or lamp) | Bacteria, viruses | 99.99% | Seconds-minutes | Moderate | Clear water only |
Chapter 5: Biosand Filter Construction
| Layer (bottom to top) | Material | Depth | Function |
|---|---|---|---|
| 1. Drainage (bottom) | Coarse gravel (12-18mm) | 2 inches | Supports sand, allows outflow |
| 2. Separator | Fine gravel (6-12mm) | 2 inches | Prevents sand entering drainage |
| 3. Filter sand | Clean sand (0.15-0.35mm) | 18-24 inches | Primary filtration (physical + biological) |
| 4. Standing water | Water above sand | 2-4 inches | Maintains biological layer (schmutzdecke) |
| 5. Diffuser plate | Perforated plate/cloth | At pour point | Prevents disturbing sand surface |
The biological layer (schmutzdecke) forms on top of the sand after 2-3 weeks of use. This living layer of beneficial bacteria is what actually kills pathogens. NEVER disturb it. If flow slows too much, scrape only top 1 inch of sand, wash, and replace.
Chapter 6: Daily Water Requirements
| Use | Gallons per Person per Day | Priority | Minimum Survival |
|---|---|---|---|
| Drinking | 0.5-1 gallon | Critical | 0.5 gallon |
| Cooking | 0.5-1 gallon | Critical | 0.25 gallon |
| Basic hygiene (hands, face) | 1-2 gallons | High | 0.5 gallon |
| Bathing | 2-5 gallons | Moderate | 1 gallon (sponge bath) |
| Laundry | 5-10 gallons | Moderate | 2 gallons (hand wash) |
| Dishes | 2-4 gallons | Moderate | 1 gallon |
| Garden (per 100 sq ft) | 5-10 gallons | Variable | Depends on climate |
| Livestock (per animal) | 5-20 gallons | High | Species dependent |
| Total comfortable | 12-30 gallons | - | 3-5 gallons (survival minimum) |
Reference Card
- Formula: Gallons = Roof area (sq ft) × Rainfall (inches) × 0.623. A 1,000 sq ft roof captures ~620 gallons per inch of rain.
- First-flush diverter: discard first 1 gallon per 100 sq ft of roof (washes off bird droppings, dust, pollen).
- Metal roofs are best for collection: smooth, non-toxic, no organic growth. Avoid lead, asbestos, treated wood.
- Storage must be opaque (no light = no algae), covered (no mosquitoes), and vented (pressure relief).
- Biosand filter: 18-24 inches of fine sand. Takes 2-3 weeks to develop biological layer. Then 99%+ pathogen removal.
- Boiling: 1 minute at rolling boil kills all pathogens. At altitude: 3 minutes (lower boiling point).
- Chlorination: 2 drops unscented bleach per quart. Wait 30 minutes. Should smell slightly of chlorine.
- Survival minimum: 3 gallons/person/day (drinking + cooking + minimal hygiene). Comfortable: 12+ gallons.
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