Adjusting irrigation schedules based on weather conditions is the best answer because LEED Water Efficiency encourages reducing outdoor potable water demand through efficient irrigation and climate-appropriate landscape strategies. Weather-based scheduling helps avoid overwatering by responding to rainfall, temperature, soil moisture, and evapotranspiration. This maintains plant health while reducing unnecessary water use. Manually operated valves are less reliable because they depend on human operation and may not respond to changing site conditions. High-emissivity plant materials is not a relevant LEED landscape-water strategy; emissivity relates to heat radiation from surfaces, not irrigation efficiency. Increasing potable water use contradicts LEED’s efficiency-first approach. Rainwater can further reduce potable water demand, but efficient scheduling is the action that directly improves irrigation efficiency.