Rainwater Harvesting Rain Barrels Calculating Just How Far Your Rain Barrel Will Go (Suppy vs. Demand)
As a general rule of thumb full rain barrel will irrigate a 10’ x 10’ area to a depth of about 5”-8” in the heavy clay soils soils of North Texas. By topdressing with compost and then applying 2-4 inches of mulch around your plants, you can reduce evaporation and help your rainwater last longer between watering.
Your sites specific soil properties, the slope of your land, the amount of sunlight an area receives, and the existing soil moisture are also important considerations in estimating irrigation demands. Use a soil moisture probe or even a long screw driver to help estimate the soil moisture around your plants and avoid watering unless the soil is dry.