According to the LEED v4: Building Design + Construction Guide, the Water Efficiency Prerequisite, Outdoor Water Use Reduction, Option 2. Reduced Irrigation, requires that a project's landscape water requirement be reduced by at least 30% from the calculated baseline for the project site's peak watering month. The baseline is determined by the Environmental Protection Agency (EPA) WaterSense Water Budget Tool, or a local equivalent for projects outside the U.S. The reduction must be achieved through plant species selection and irrigation system efficiency1. References: LEED v4: Building Design + Construction Guide, Water Efficiency Prerequisite, Outdoor Water Use Reduction, Option 2. Reduced Irrigation, Requirements1