Chapter 11 Fresh Water

The Water Cycle

Water on Earth 97% of all the water found on Earth’s surface is salt water. 3% of all the water found on Earth’s surface is fresh water. Less than 1% of fresh water is available for human use.

The Water Cycle In the water cycle, water moves from bodies of water, land, and living things on Earth’s surface to the atmosphere and back to Earth’s surface. Water on Earth is naturally “recycled” through the continuous process of the water cycle.

Main steps of the Water Cycle Precipitation: When water droplets are heavy enough they fall back to Earth as rain, snow, sleet, or hail. 1. Water that is absorbed is called groundwater. 2. Water that is not absorbed is called runoff and will collect in bodies of water.

Main steps of the Water Cycle Evaporation: The process when molecules at the surface of a liquid absorb enough energy to change to a gaseous state. Liquid water is constantly being turned into a gaseous state, called water vapor, from bodies of water and carried into the atmosphere.

Main steps of the Water Cycle Evaporation: 2. Most evaporation occurs over the ocean. 3. Minerals (salt) dissolved in water remain behind as the liquid water is changed into a gas, water vapor.

Main steps of the Water Cycle C. Condensation: Clouds form as the water vapor cools. The higher up in the atmosphere the colder the air. Cold air holds less moisture than warm air. 2. Water vapor condenses (squeezes) into liquid droplets around dust particles, forming clouds.

The energy from the sun is the source that drives the water cycle. Water molecules stay in the atmosphere for roughly 10 days before they start their journey over. Water is essential for living things to grow, reproduce, & carry out important processes.

Water on the Surface

River Systems Tributaries are the smaller streams and rivers that feed into a main river. A river and all of its tributaries make up a river system.

River Systems The land area that supplies water to a river system is called a watershed. One watershed is separated from another by a ridge of land called a divide.

Floods A flood occurs when the volume of water in a river increases so much that the river overflows its channel. Flooding can be “controlled” through the building of dams and the natural build-up of sediment (levees). Heaviest/largest sediments are deposited first: Gravel, sand, silt, clay, etc.

Lakes Lakes form in many ways: cut-off meander, glaciers, tectonic plate movement, volcanoes, and man-made (reservoir).

Lakes and Turnover Lake water changes temperature with the seasons. Forming convection currents, causing the water to mix minerals, plant matter, and other nutrients as they rise from the bottom to the surface and is called LAKE TURNOVER. This refreshes the supply of nutrients.

Lakes and Eutrophication Eventually, the nutrients build-up allowing a thick layer of algae to grow. When the algae is thick enough they prevent the plants from carrying out photosynthesis. The decaying of dead organic material reduces the amount of dissolved oxygen in the water.

Lakes Eventually organisms cannot survive and the lake turns into a meadow. This process is called eutrophication.

What is an iceberg? Floating Ice. Why is it hazardous to ships? 90% of the iceberg lies below the water.

Water Underground

Underground Layers Water underground trickles down between particles of soil and through cracks and spaces in layers of rock. Different types of rock and soil have different-sized spaces, pores.

Underground Layers How easily water will pass through depends on: Pore size Pore connectivity

Underground Layers Materials that allow water to pass through are called permeable. Examples: Sand Gravel

Underground Layers Materials that water cannot pass through easily are called impermeable. For example: Clay and Silt

Underground Layers Once water reaches an impermeable layer, it is unable to soak deeper and begins to pool. The area of permeable rock/soil that is totally filled saturated, with water called the saturated zone.

Underground Layers The top of the saturated zone is called the water table.

Underground Layers The layer of rock and soil above the water table is called the unsaturated zone/zone of aeration.

Aquifers Any underground layer of rock or sediment that holds water is called an aquifer.

Aquifers Groundwater is moving. How fast it moves depends on: The slope The permeability of materials

Springs The place where the water table meets the ground surface, ground water bubbles or flows out of cracks in rock called springs.

Wells People can obtain groundwater from an aquifer by drilling a well below the water table.

Wells Pumping water out of an aquifer lowers the water level near the well. If too much is pumped out, too fast, the well may run dry.

Recharge The place or process where new water enters and replenishes the aquifer is called recharge.

Artesian Wells Groundwater is trapped between two layers of impermeable rock layers. The water is under intense pressure because of the weight of water above it. If the top impermeable layer is punctured the water shoots out, under pressure.

Vocabulary Term – look up

Evaporation – pg. 309 The process by which water from the oceans and Earth’s surface absorb enough energy to change into water vapor.

Groundwater – pg. 320 The water located within the rocks below Earth’s surface.

Precipitation – pg. 309 Forms of water such as rain, snow, sleet, and hail that fall from clouds and reach Earth’s surface.

Saturated Zone – pg. 320 Area in which the spaces between rock particles are filled with water.

Spring – pg. 322 A place where the water table reaches Earth’s surface and water flows from the ground.