Integrating rainwater harvesting into your irrigation system design can significantly reduce your water demand and reliance on potable water. Install a rainwater collection system, such as a rooftop collector or underground tank, to capture and store rainwater. Connect the harvested water to your irrigation system, ensuring proper treatment and filtration to prevent contamination. Consider using a first flush device to divert initial rainfall runoff, which may contain debris and contaminants, and allow cleaner water to enter the storage tank. By incorporating rainwater harvesting, you can create a more sustainable and resilient irrigation system.