Learn the ins and outs of lawn irrigation and effective watering. Water Guzzlers Lawns are water guzzlers. On average, most lawns need 1 to 1.5 inches of water per week to stay lush and green. That water can come from rainfall or irrigation. How often your lawn needs a drink depends on many factors, including things like soil type, sunlight, grass type and regional climate. The list truly goes on and on. In many municipalities, water restrictions are the norm, and lawn waterin...