Lawn irrigation needs vary by grass type. In general, warm-season grasses need about 20 percent less water than cool-season types. Tall fescue, if it’s healthy, develops a deep root system that gives this grass type the highest drought tolerance among cool-season grasses. Bermuda, centipede, St. Augustine and zoysia warm-season grasses also develop strong, deep root systems that enable these grasses to withstand drought. Other grasses, like Kentucky bluegrass, go dormant during times of drought and revive when irrigation returns.