This book presents the main concepts of water footprint, ecological footprint, carbon footprint, virtual water and the Ipai model (Integrated Environmental Footprint Index). Ipai model covers the water, ecological and carbon footprints of heterogeneous communities of Paraíba, small, medium and large cities of Paraíba and countries by continent. With an accessible language, it analyzes deeply the indices of water, ecological, carbon and Ipai footprints.