Human Impact on The Water Cycle

Why is the Water Cycle SO Important? 75% of the Earth is covered with water and 97.5% of that is salt water. The majority of fresh water 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 land, air, and sea.

(Trust) The Processes Evaporation Condensation Transpiration Precipitation

Evaporation Process in which liquid changes to gas (vapor). Any water on the Earth’s surface will evaporate.

Transpiration A process caused by the evaporation of water from leaves of plants and its uptake from roots in the soil. The amount of water lost by a plant depends on its size, along with the available light intensity.

Condensation Condensation is the process by which matter changes from a gas into a liquid. E.g. dew on the grass, a cold glass of water Condensation occurs on a glass when the air(gas) outside the glass is warmer than the substance inside the glass. Also, when the air outside of the car window is cooler than the air inside the car this creates dew on the inside of the 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 (rain, snowmelt) that flows over the land surface. This is a major component of the water cycle. When the ground is saturated, the water flows into lakes, streams, rivers, and oceans. Water flows to the lowest point it can find. This could be lakes, streams, rivers, oceans.

Groundwater The water that is filtered through the soil and remains underground 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. Humans, bears, birds, and fish. You influence what happens in your watershed in the way you treat the natural resources. What happens in your small watershed also affects the larger watershed downstream.

Human Impact on Water Dumping waste onto the land which will filter down into the groundwater, polluting the run-off in a watershed that will go into other bodies of water and pollute it as well.

Human Activities that Impact the Water Cycle Surface water and groundwater pollution has two main sources: Use of toxic chemicals in agriculture and manufacturing. Runoff from chemical fertilizers and pesticides can pollute or seep into the ground to contaminate the water supply.

Clear-cutting forests reduces the amount of water that plants can return to the atmosphere by transpiration.

Don’t Forget the Oceans!

Runoff Runoff is the excess water that carries pollutants into storm drains and then to the ocean. 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 wastewater flows to the curb it carries POL’s, trash, fertilizers, pet waste and other pollutants into the stormwater system which eventually flows into the ocean. As runoff increases, infiltration, or the absorption of water back into the soil, decreases. This also prevents the replenishing of groundwater.

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 algal blooms. When they die, they decompose in a process that robs the water of its oxygen. Fish can’t live in areas with low O2 levels.

Bacteria can wash into swimming areas, making beach closures necessary. Debris such as plastic bags, six-pack holders, and cigarette butts can wash into water bodies and choke, suffocate, or disable ducks, fish, turtles, and birds. Household hazardous wastes like used motor oil, insecticides, pesticides, paint, and solvents can poison aquatic life.