Understanding groundwater and watersheds and how we monitor, assess, and sustainably manage these resources is critical and integral to California Groundwater Sustainability Plans (GSPs) and other water management programs. Private citizens, professionals, decision makers, executives, agency employees, and stakeholders with diverse backgrounds and in a wide variety of private, non-profit, and government responsibilities are increasingly engaged in the sustainable management and assessment of groundwater and surface water. This online short course will review the fundamental principles of groundwater and watershed hydrology, water budgets, water quality, and water law and regulation in an intuitive, highly accessible fashion. Through real world examples, participants learn about the most common tools for measuring, monitoring, and assessing groundwater and surface water resources. We then review the key steps and elements of planning for groundwater sustainability.