Last week I penned a post on water conservation. I had been digging up the dry spots in the lawn and removign clay layers and stumps that impede the growth of roots.
Bradley Ross made the astute observation that underground rocks are also a big problem.
An extension of that observation is that rocks on top the ground can help conserve water.
In the desert, one battles the forces of evaporation. Rocks atop the soil can help hold in moisture while reducing the number of plants (weeds) competing for water.
When placing rocks, the goal is to creat a design with places that concentrates and holds water from the wet season into the dry season.
The rock garden is the preferred landscape design in the dry mountain west for more than just aesthetic reasons.