Conserving Water by Mimicking Mother Nature
by Doug Pushard
One of the biggest potable water uses is outdoor irrigation. There are many mechanical and active ways to reduce this water use but maintaining healthy soil has not been talked about as a popular method.
For example, installing a rainwater harvesting system, installing a gray water system, upgrading your irrigation system with rain and moisture sensors; replacing plants with more drought-tolerant ones; or simply adding a few more inches of mulch around your plants are popular methods. These are all great improvements and all will definitely result in a lower water bill.
However before you do any of these you might consider fixing your soil. Soil is the biggest, most natural sponge of water.
Studies have shown that healthy soil absorbs and retains far more water than unhealthy soils. Not just 10 or 20% but up to 50% more in some studies. Can you imagine cutting your outdoor water consumption by over 50%? Not only would this result in a significant drop in your water bill, it would be beneficial for your plants.
A recent study done at the Santa Fe Community College showed that by installing rain gardens or rain retention basins more water was retained in the soil. Rain gardens and retention basins are depressions (i.e. 6”-18” deep) in the soil for capturing water. The study, Stormwater Irrigation: Can Retention Basins Significantly Improve Soil Moisture, measured the amount of moisture stored in the ground near retention ponds versus adjacent flat undisturbed soil. This study concluded that these basins would capture over 13,000 gallons a year, but also this moisture was retained far longer.
Instead of building dams around trees, build a depression to capture and retain the water. These simple structure can be used anywhere to retain and allow rainwater to infiltrate slowly. The study highlighted the fact that catchment basins could sustain mature trees in the absence of irrigation systems. These catchment basins stored between 8 and 16 days of extra water versus the native surrounding soil without basins.
For this study two retention basins were constructed off the parking lot of the Santa Fe Community College Kid’s Campus. Rainwater is fed to these basins through curb cuts. Adjacent to these basins are curb cuts that allowed stormwater to exit on to the native grassland off the parking lot. These sites were used for this study and the retention basins are still in use today.
Aaron Kaufmann, Founder of Southwest Urban Hydrology states "this study highlights the numerous benefits of retaining stormwater onsite rather than letting it run downstream as it does in our current urban designs. This one change can have substantial benefits for the homeowner, our neighborhoods and our community."
Besides the significant water savings benefit that these easy to construct features provide, they also improve plant health, increase pollinator habitats, reduce the use of expensive potable water for irrigation, and can increase carbon sequestration through the planting of trees alongside these spaces. A copy of this study can be downloaded at: http://www.southwesturbanhydrology.com/
Saving water is crucial these days. There are many, many ways of going about it. Mimicking nature through the construction of rain basins is a simple one that can benefit us all. These easy to build landscape features can save precious water and help the environment. A win-win solution.