The Iowa Department of Natural Resources has released a set of tips for watering trees during drought conditions.
They advise using buckets of water or a hose instead of sprinklers, since sprinklers are less efficient.
An area within and just beyond the canopy should be watered with one gallon of water per square foot. This should be done in the evening or early morning to avoid evaporation.
On weeks with no rainfall, trees should be watered one to three times.
Read more tips on watering trees here.