Communities across the United States are faced with decisions about building water infrastructure to meet the needs of a growing population. To help make these decisions, water utilities often rely on forecasts that project water use 20 or 30 years into the future. The Pacific Institute has created this guidebook to encourage community involvement in water infrastructure decisions based on demand forecasts. The guidebook gives background information on the practice of demand forecasting, and provides a list of questions that are helpful to evaluate the quality of a water demand forecast.