Water has many important uses including drinking, cooking, washing utensils, bathing, cleaning, and is found in rivers, oceans, ponds, wells, lakes, and seas. The process of water turning into vapor is called evaporation, while the process of vapor turning back into water is called condensation. Transpiration is the process by which leaves release water vapor into the atmosphere. When it rains heavily for a long period, it causes flooding. Drought occurs when there is no rain for an extended time. Groundwater is rainwater that gets absorbed into the soil. Rainwater collection systems involve collecting roof rainwater in pipes that lead to storage tanks, which may require filtering before use.