Rain Harvest Calculator: Understanding Rainwater Collection

What is Rainwater Harvesting?

Rainwater harvesting is the process of collecting and storing rainwater for later use. It's an eco-friendly practice that can reduce reliance on municipal water supplies and help conserve water resources. This calculator helps estimate the potential volume of rainwater that can be collected from a roof surface during a rainfall event.

Formula and Variables

The basic formula for calculating harvested rainwater volume is:

\[V = A \times R \times E\]

Where:

• \(V\) is the volume of harvested rainwater (in liters or gallons)
• \(A\) is the roof area (in square meters or square feet)
• \(R\) is the rainfall amount (in millimeters or inches)
• \(E\) is the collection efficiency (as a decimal, typically 0.8 or 80%)

Calculation Steps

1. Measure or estimate the roof area.
2. Determine the rainfall amount for a specific period.
3. Decide on a collection efficiency (usually 80% to account for losses).
4. Multiply these three factors together.
5. Convert the result to the desired volume unit if necessary.

Example and Visual Representation

Let's calculate the harvested rainwater for:

• Roof Area: 100 m²
• Rainfall: 50 mm
• Efficiency: 80%

\[V = 100 \text{ m}^2 \times 50 \text{ mm} \times 0.8 = 4,000 \text{ L}\]

This diagram illustrates the concept of rainwater harvesting. The brown shape represents the roof collecting rainwater, which is then stored in the blue tank below. The volume of 4,000 liters represents the amount of water that could potentially be harvested from this roof during a 50 mm rainfall event.