To aid deep watering on sloping sites, and aerate for roots, consider this method. Insert perforated plastic pipe and fill with medium-sized gravel. This method will insure that the water you put on the ground will penetrate the 12 inches necessary for good root zone moisture content. Mulch is another way to conserve moisture near your trees and shrubs. Mulch is any material placed on the soil to cover and protect it.
Common mulches are bark, wood chips, ornamental gravel, and landscape matting.
Mulching will also help with weed and grass control and protect the lower portions of your trees and shrubs from mechanical injuries. When all else fails, and you lose a tree or shrub to drought stress, take the time to replace the planting with a more suitable drought tolerant species. Drought tolerant species include bur oak, Gambel oak, blue oak, black and honey locust, Rocky Mountain juniper, Austrian pine and ponderosa pine. Drought intolerant species include the birches, cottonwood and poplars, spruces and fir. In the case of deep watering your trees and shrubs before winter it proves only too true.