Rainwater is the lifeblood of the garden. The pH is optimal for garden plants, and the soluble nutrients provide a nice boost. But rain is anything but predictable. The clouds roll in and you think you’re in luck only to get a drop or two. Other times, out of nowhere the drops start falling from a clear sky.
So when you’re lucky enough to get substantial rainfall, how do you measure it? And with a proper measurement, how can you estimate the amount you can collect? And if you can calculate the amount you might collect in a year, how does that relate to your usage in the Lab?
Ways to Measure Rainfall
Measuring rainfall is
simple difficult a challenge and there are several methods you can use. Here are two methods to use with your class.
- DIY rain gauge
- Wireless digital rain gauge
How to Calculate Collection Potential
One of the more interesting projects relating to rain harvesting is the calculation of potential. Here are the constants and variables you will need to consider.
- Measure square footage of rooftop
- Measure rainfall
- Use factor of .623
- Apply efficiency factor
To calculate collection potential, multiply: square foot of collection area x rainfall (in inches) x 0.623 x efficiency factor for collection type = gallons (The efficiency factor is approximately 90% for most roof types because most of the water is collected.)
- Roof area = 1,000 sq ft
- Annual Rainfall = 15 inches
- Apply formula: 1,000 sq ft x 15 inches x 0.623 x 0.90 = 8,140 gallons/year