This document discusses different funding structures for water infrastructure investments, including public-private partnerships (PPPs) and public funding. It provides an overview of how PPPs work, including the typical project financing structure. It notes that PPPs have historically had lower default rates than other project financing. The document also outlines some costs and benefits of the PPP model compared to public funding. Finally, it discusses some tools for public financing of water infrastructure projects in the United States, such as grants, loans, bonds, and subsidies.