The Sumerians made many important advances for early civilization. First, they developed irrigation by building canals from rivers and reservoirs, which allowed for agriculture in arid regions. Second, they invented the concept of libraries to store and organize their extensive writings on religion, laws, business, and history. Third, they were the first to use contracts to legally formalize business transactions and protect both parties. Lastly, the Sumerians were the first to effectively use the wheel in applications like carts and plows to increase efficiency in transportation and farming. However, their military defenses were inadequate, contributing to the eventual decline of their civilization.