The document discusses the water cycle and its key processes. It describes how water evaporates from surfaces due to heat from the sun, condenses to form clouds, precipitates as rain, snow or hail, and either runs off on the surface or infiltrates into the ground to replenish groundwater stores or be absorbed by plant roots through transpiration. It then focuses on groundwater, describing it as water residing in saturated underground areas, and how it is stored in aquifers. It identifies sewage as a major cause of groundwater pollution.