What are the advantages and disadvantages of withdrawing groundwater? Describe the problem of groundwater depletion in the world and in the United States, especially in the Ogallala aquifer. Describe ways to prevent or slow groundwater depletion. What is a dam? What is a reservoir? What are the advantages and disadvantages of large dams and reservoirs? Define desalination and distinguish between distillation and reverse osmosis as methods for desalinating water. What are three limitations of desalination.