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Fig 9-3
•Arguably the most important natural phenomenon on Earth, the water cycle, also known as the hydrologic cycle, describes the constant movement and endless recycling of water between the atmosphere, land surface, and under the ground.
•The hydrologic cycle supplies the force needed for most natural processes, thus supporting life itself.
The Water Molecule H20 consists of one
atom of oxygen bound to two atoms of hydrogen.
The water molecule has a positive charge on the side of hydrogen atoms and a negative charge on the other side.
Water molecules tend to attract each other because the positive ends attract to the negative ends.
Water is a “universal solvent: and wherever it goes throughout the water cycle, it takes up valuable chemicals, minerals and nutrients.
The change from a liquid to a gas. In the water cycle, the change from water to water vapor.
Condensation & Convection Warm air rises
Air cools and can no longer hold vapor
Process known as CONVECTION
Condensation & Cloud Formation
Cooling of water vapor forms CLOUDS
Other ways clouds are formed Convergence Lifting of air
by fronts
Snow Snow is a type of
precipitation like rain but at cooler temperatures
Usually reaches the ground and stays
Eventually melts and becomes runoff in streams
Rain Type of
precipitation during warmer weather
Occurs when clouds become too full
Falls to earth in the form of water and runs off to streams & rivers
Freshwater Storage Water may be
stored temporarily in the ground, oceans, lakes, rivers, and ion ice caps and glaciers.
The world’s two main reservoirs of fresh water are the great polar ice caps, and the ground.
If all of the ice in the ice caps and other glaciers melted, it would raise the sea level by about 260 ft.
In temperate climates, water is found in depression storage or surface water puddles, ditches, and anywhere else that runoff water can gather.
This is a temporary form of storage
Freshwater Flow
A hydrologist is particularly interested in stream flow -- the 31% of precipitation which runs off into rivers, streams and lakes.
About 3% of this water will seep underground
About 31% will run off into rivers, streams and lakes
About 66% of the water returns to the atmosphere through evaporation and transpiration
Surface Runoff When
precipitation rate exceeds infiltration rate, or when soil is saturated, water begins to move down slope on ground surface.
Surface Runoff surface runoff
gradually flows into gullies, streams, lakes, or rivers. Water in streams and rivers flows to the ocean, seeps into the ground, or evaporates back into the atmosphere.
Water Storage in Oceans
The largest reservoir is the oceans. There is about 50 times as much water in the oceans than in the next largest reservoir, polar ice and glaciers.
Water Storage in Ice and Snow
Water precipitates into cooler areas of land and freeze into ice and snow.
Snowmelt Runoff to Streams
Precipitation falls in the form of rain and snow
When the snow melts it runs into streams which eventually dump into the ocean
-Rain water soaks into ground through soil and underlying rock layer.
-Water cleaned as impurities filtered
-Some water remains underground as groundwater.
-Some water returns to surface at springs or low spots downhill.
Groundwater Storage
-then stored underground in rock crevices and in the pores of geologic materials that make up the Earth's crust
- water seeps downward underground into soil and rock crevices
-Water storage under the ground largely depends on the geologic features related to the types of soil and the types of rocks present at the storage locations.
-underground storage occurs in the soil, in aquifers, and in the crevices of rock formations
Evaporation Conversion of
water from a liquid into a gas
Water transferred from surface to atmosphere through evaporation
Evaporation & the Sun The sun heats
up water in the ocean, rivers, or lakes, turning it into vapor, which then goes into the air
Evaporation
Cont. 80% of
evaporation from ocean
20% of evaporation from inland water and vegetation
Winds transport evaporated water, influencing humidity around the world
TranspirationThe process of evaporation from plants. Basically, plants sweating.
Transpiration Cont.Environmental
factors that affect transpiration:
Light Temperature Humidity Wind Soil water
Good For Plants!! Transpiration is
the “engine” of plant life, pulling water up from the roots. This allows for photosynthesis, brings minerals from the roots to the rest of the plant, and cools the leaves.
Water Storage in
Atmosphere
-atmosphere holds only very small percentage of Earth’s water supply at any given time
World Water Supply
Source % of Supply
Oceans 97.08
Ice Sheets and Glaciers 1.99
Ground Water 0.62
Atmosphere 0.29
Lakes (Fresh) 0.01
Inland Seas / Salt Water Lakes 0.005
Soil Moisture 0.004
Rivers 0.001
-rapid recycling of water must occur between earth's surface and atmosphere
- Water stored in the atmosphere can be moved relatively quickly from one part of the planet to another part of the planet
Water Pollution