Harvesting rainwater can reduce the use of drinking water for landscape irrigation. Coupled with the use of native and desert-adapted plants, rainwater harvesting is an effective water conservation tool because it provides "free" water that is not from the municipal supply.
 
There are many benefits to harvesting rainwater. Water harvesting not only reduces dependence on ground water and the amount of money spent on water, but also reduces off-site flooding and erosion by holding rainwater on the site.

If large amounts of water are held in highly pervious areas (areas where water penetrates easily), some of the water may percolate to the water table. Rainwater is a clean, salt-free source of water for plants.
 
In addition, rainwater harvesting can reduce salt accumulation in the soil which can be harmful to root growth. When collected, rainwater percolates into the soil, forcing salts down and away from the root zone area.

This allows for greater root growth and water uptake, which increases the drought tolerance of plants. Limitations of water harvesting are few and are easily met by good planning and design.