Dams are large structures built across rivers or streams to hold back water, creating reservoirs for various purposes such as irrigation, flood control, and hydroelectric power generation. They play a crucial role in managing water resources and can significantly impact the surrounding environment and communities. The construction of a dam involves careful planning and engineering to ensure safety and efficiency. Some well-known examples include the Hoover Dam in the United States and the Three Gorges Dam in China. These structures not only provide essential services but also create recreational opportunities and habitats for wildlife.