Surface and Ground Water

Water is one of the major agents involved in erosion. Sediments are carried, transported, and deposited by rivers and streams. About 70% of the Earth’s surface is water. About 97% of Earth’s water is saltwater and 3% of Earth’s water is fresh water. About 77% of our fresh water is frozen in the polar ice caps. Only about 0.7% of the total water on Earth is readily available for use by humans and other species that rely on fresh water as a resource.

The water cycle is a cycle through which there is constant movement of water between oceans, bodies of fresh water, the atmosphere, and the solid portion of the Earth. The overall amount of water on Earth stays roughly the same. Sun provides the energy that fuels the water cycle. Heat from the sun evaporates water from lakes, ponds, oceans, rivers, moist soil surfaces, and plants. Transpiration is a process by which plants add water vapor to the atmosphere. Plants take up water from the soil. Any unused water then passes out of small holes in the plant’s leaves, evaporates, and becomes water vapor in the atmosphere.

Water vapor cools in the atmosphere and condenses to form water droplets in clouds. When clouds meet cold air the water returns to the Earth again in the form of precipitation. The precipitation may then evaporate, collect in bodies of water on the Earth’s surface or soak into the soil. Surface Water is the water that is above ground in lakes, ponds, rivers, and streams. Groundwater is a layer of underground water that has seeped so far into the surface of the Earth that is has reached a layer of rock or clay and cannot go any farther. Groundwater is often stored in aquifers. They contain large amounts of ground water in underground rock formations. Aquifers are usually porous rocks but they are sometimes large caves. It takes a very long time for them to form. The recharge zone is the area of land where groundwater originates. Watch the video to learn more about the water cycle and complete the Groundwater Use and Overuse Activity.

Take notes as you watch the Hydrologic Cycle Interactive and Water Cycle Animation below.