Water on Earth is found in three main places: rivers, lakes, and oceans. Rivers are flowing water that moves downhill across the land, often starting from mountains or springs and ending in a lake or ocean. Lakes are large bodies of still water surrounded by land. Oceans are the enormous saltwater bodies that cover most of Earth's surface. Together, these water bodies are connected through the water cycle and play essential roles in weather, climate, and supporting life.
Use maps and globes to locate major rivers, lakes, and oceans. Build a simple landscape model with clay to show how water flows downhill from high ground into rivers and lakes. Compare freshwater (rivers and most lakes) to saltwater (oceans) using taste-safe salt experiments. Visit a local stream, lake, or coastline if possible.
Look at a globe or a map of Earth and the first thing you notice is blue -- water covers most of our planet. That water is found in three main types of bodies: rivers, lakes, and oceans. Each one plays a different role, and together they form the water network that keeps Earth alive.
Rivers are water in motion. They start in high places -- mountaintops, hills, or underground springs -- and flow downhill, always downhill, following the pull of gravity. Small streams trickle together to form creeks, creeks join to become rivers, and rivers can grow enormous. The Mississippi River, for example, gathers water from streams across nearly half of the United States and carries it to the Gulf of Mexico. Rivers are important because they carry freshwater across the land, providing water for plants, animals, and human cities along their banks.
Lakes are bodies of water surrounded by land. Unlike rivers, lakes do not flow in one direction -- they sit in low spots in the landscape where water has collected. Some lakes are formed by rivers that flow into basins with no easy outlet. Others were carved by glaciers long ago. Most lakes contain freshwater, which is the water people, animals, and plants need to survive. Some lakes, like the Great Salt Lake in Utah, are salty because water flows in but can only leave by evaporation, leaving dissolved salts behind.
Oceans are the giants. They are vast bodies of saltwater that cover about 71% of Earth's surface. Although we give them different names -- Pacific, Atlantic, Indian, Southern, and Arctic -- they are all connected into one global ocean. The ocean is critically important for weather: the sun heats the ocean surface, causing evaporation that puts water vapor into the air, which eventually forms clouds and brings rain to the land. Without the ocean, there would be far less rain and most of the land would be desert.