The Water Cycle and How Humans Impact It 7.8C Model the effects of human activity on groundwater and surface water in a watershed
The Water Cycle (Hydrologic Cycle): How Water is Naturally Recycled on Earth
Why is the Water Cycle so Important? • 2/3 of the Earth is covered with water and 97.5% of it is salt water. • The majority of freshwater is beyond our reach, frozen into glaciers and polar caps. • The water cycle is the natural circulation of water on Earth: the constant circulation of water between atmosphere, land, and sea.
The processes of the Water Cycle Evaporation Condensation Transpiration Precipitation
Evaporation • Process in which liquid changes to gas (vapor) • Any area of water on the earth’s surface will evaporate
Transpiration • A continuous process caused by the evaporation of water from leaves of plants and its corresponding uptake from roots in the soil. • The amount of water lost by a plant depends on its size, along with the surrounding light intensity (radiant energy).
Condensation • Condensation is the process by which matter changes from a gas (or vapor) phase into a liquid phase. • Ex. Dew on the grass in the morning, cold glass of liquid, fog on the inside of a car window
Precipitation • When cloud (water molecules) particles become too heavy to remain suspended in the air, they fall to the earth as precipitation.
Surface Run-off • Water, from rain, snowmelt, or other sources, that flows over the land surface, and is a major component of the water cycle. • When the ground is saturated, the water flows into lakes, streams, rivers, and oceans.
Groundwater • The water that is filtered through the soil and remains under the ground for plants to use. • Is a major source of drinking water as well as agricultural irrigation.
What is a Watershed? • A watershed is simply a place where water drains into one spot, such as a lake or ocean. • Everyone lives in a watershed. The animals, birds, and fish do too. • You influence what happens in your watershed, good or bad, by how you treat the natural resources, the soil, water, air, plants, and animals.
Human Impact on Water Look at the picture and list some ways that humans impact the surface water and groundwater.
Human Activities that Impact the Water Cycle • Use of toxic chemicals in agriculture and manufacturing and runoff from chemical fertilizers and pesticides can pollute surface water or seep into the ground to contaminate groundwater • Clear-cutting forests reduces the amount of water plants return to the atmosphere by transpiration.
Oceans Human Activities Affect the Ocean, Too! Humans depend on the ocean for food, recreation, trade, travel, and jobs. Many human activities have modified (changed) the ocean.
Runoff • Runoff is the excess water that carries pollutants into storm drains and then to the ocean. • It is an environmental problem for all communities. Residents who live miles inland can contribute to ocean pollution simply by leaving their sprinklers on too long, washing cars at home, or hosing down driveways. • After this wasted water flows to the curb it carries trash, fertilizers, pet waste and other pollutants into the storm drain system which eventually flows into the ocean.
The negative effects of runoff pollution • Sediment can cloud the water and make it difficult for aquatic plants to grow and can destroy aquatic habitats. • Excess nutrients can cause algae blooms. When they die, they decompose in a process that robs the water of its oxygen. Fish can’t live in areas with low oxygen levels. • Bacteria can wash into swimming areas, making beach closures necessary. • Debris such as plastic bags, six-pack bottle rings, and cigarette butts can wash into water bodies and choke, suffocate, or disable ducks, fish, turtles, and birds. • Household hazardous wastes like insecticides, pesticides, paint, solvents, and used motor oil can poison aquatic life.
What can you do? Recycle or properly dispose of household materials and wastes. Don’t dispose of them in sinks or toilets. Don’t overwater your lawn or use too many pesticides or fertilizers. Don’t wash your car at home. Pick up pet waste and dispose of it properly (flushing).