After rain, some water goes into the ground. This is called infiltration. The rest flows over the ground into streams and rivers. Very little water passes through a sealed surface, such as an asphalt playground. During heavy rain, a lot of water can quickly go into drains. A planted area can take in water and hold it for a short time. Plants also send some water from their leaves into the air. This is called evaporation. This helps cool the area. How much water goes into the ground depends on the soil and how wet it is. Even a green area may not take in all the water during heavy rain.