Rainwater Harvesting in Cochise County

To calculate your total potential rainwater collection, use this standard formula based on your surface area and local annual rainfall: gallons collected = collection area (sq. ft.) x rainfall (inches) x 0.623 x 0.90.

• Square footage: Measure the length and width of your roof or impermeable surface (L x W).
• Conversion factor (0.623): Represents gallons of water per square foot at 1 inch deep.
• Efficiency factor (0.90): Accounts for a standard 10% loss to evaporation, absorption, and initial roof wash.

Example calculation: A 1,000 sq. ft. roof receiving 15 inches of rain per year yields roughly 8,410 usable gallons annually (1,000 x 15 x 0.623 x 0.90).

Need a personalized calculation? Email Caitlin Brady at cbrady17@arizona.edu to request our custom water budget calculator.

Earthworks and permeable materials can naturally sink rainwater directly into your soil to support trees and garden beds:

• Porous paving: Use bricks, pervious pavers, or specialized asphalt to let rain filter directly into the ground.
• Hardscape contouring: Angle patios, paths, and driveways toward planted basins rather than public storm drains.
• Privacy wall management: Temporarily block lower wall drainage weep holes during storms to hold runoff in your yard longer, allowing deep soil soaking without causing home flooding. 

Keep stored rainwater clean and pest-free with these preventative steps:

• Mosquito control: Cover all container openings with fine mesh screen. For open water, add Mosquito Dunks (a natural Bacillus thuringiensis israelensis microbial insecticide safe for plants).
• Algae prevention: Use opaque tanks to block sunlight. If using translucent white plastic containers, paint the exterior with tinted rubberized roof paint.

Whether you need a pump depends on how you plan to apply the water:

• Gravity-fed systems (no pump): Ideal for basin flooding, hose discharge, or low-pressure T-Tape drip lines that operate between 2–10 PSI.
• Pressurized systems (pump required): Standard home drip irrigation, soaker hoses (requiring 15–20 PSI), and all indoor household plumbing (requiring 30+ PSI) need an automated electric pump.

A simple, non-potable gravity system requires six core elements:

1. Gutters and downspouts: Route water off the roof.
2. Debris screens: Filter out leaves and large dirt particles.
3. Storage container: Rain barrels or larger polyethylene/metal tanks.
4. First-flush diverter: Routes the initial dirty runoff away from the tank.
5. Tank overflow: Directs heavy excess water safely away from foundations.
6. Drainage distribution: Gravity hoses or pipes leading to garden beds.

Yes, but drinking systems require complex filtration, approved materials, and regular maintenance:

• Roof selection: Use non-toxic metal roofs like stainless steel, galvalume, or coated galvanized steel. Avoid lead, zinc, or copper.
• Plumbing: Run Schedule 40 PVC from the tank (avoid copper or ABS pipe).
• Filtration and treatment: Use a high-pressure pump (minimum 30 PSI), sediment filters, and a final stage ultraviolet (UV) light disinfection system.

Before purchasing hardware, evaluate these key site questions:

• Intended use and scale: Will the water be used for outdoor plants or indoor plumbing? Do you want room to expand later?
• Placement and space: Above ground or buried? Can tanks serve double duty as shade walls, windbreaks, or property borders?
• Aesthetics and regulations: Do local HOA rules or city codes dictate hiding or painting storage tanks?
• Flow and elevation: How will water travel from roof downspouts to the tank and out to plants—gravity or pump?

• The Discovery Gardens at The University of Arizona Cooperative Extension Sierra Vista
• Sierra Vista Self-Guided Rain Harvesting Tour
• City of Bisbee RWH Fact Sheet
• Cochise College RWH Fact Sheet
• Naco Border Patrol RWH Fact Sheet
• Sonic Drive-In RWH Fact Sheet
• Sierra Vista Police Station RWH Fact Sheet
• Huachuca City Community Garden