Rainwater Harvesting Rain Barrels Determining Supply vs. Demand

Supply

A simple calculation can be used to estimate the potential amount of rainwater which could be collected fr om each downspout or roof section. For most homes in North Texas you can fill up several rain barrels in a single rainfall event.

.6 gallons per square foot roof per 1” rainfall
2,000 sq. foot roof X 1" rain = 1,200 gal. water
1,200 gal. X 37" rainfall per year= 44,400 gal/yr

Another way to think of it: a 55 gallon barrel can be filled up by about 200 sq ft of roof area in a .05” rainfall event, or about 100 sq ft of roof area in a 1” rainfall event.

Demand

Plant Water Requirements: The types and numbers of plants in your landscape, along with their growth stages and sizes, determine the amount of water your plants need to be healthy. Because rainfall varies throughout Texas, different plants have become adapted to conditions in different regions of the state. Plants native to your region are the best choices for your landscape because their water requirements are usually met by normal rainfall amounts during most times of the year. There are also many adapted plants which thrive in our unique climate but are native to areas with similar soil types, hardiness zones and rainfall patterns. For a list of our favorite Native and Adapted plants check out our plants selection page.

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