Water Cycle

The earth's water supply remains constant, but man is capable of altering the cycle of that fixed supply. Population increases, rising living standards, and industrial and economic growth have placed greater demands on our natural environment. Our activities can create an imbalance in hydrologic equation and can affect the quantity and quality of natural water resources available to current and future generations.

Water use by households, industries, and farms has increased. People demand clean water at reasonable costs, yet the amount of fresh water is limited and the easily accessible sources have been developed. As the population increases, so will our need to withdraw more water from rivers, lakes and aquifers, threatening local resources and future water supplies.

A larger population will not only use more water but will discharge more waste water. Domestic, agricultural, and industrial wastes, including the intensive use of pesticides, herbicides and fertilizers, ofter overload water supplies with hazardous chemicals and bacteria. Also, poor irrigation practices raise soil salinity and evaporation rates. These factors contribute to a reduction in the availability of potable water, putting even greater pressure on existing water resources.

Large cities and urban sprawl particularly affect local climate and hydrology. Urbanization is accompanied by accelerated drainage of water through road drains and city sewer systems, which even increases the magnitude of urban flood events. This alters the rates of infiltration, evaporation, and transpiration that would otherwise occur in a natural setting. The replenishing of ground water aquifers does not occur or occurs at a slower rate.

Together, these various effects determine the amount of water in the system and can result in extremely negative consequences for river watersheds, lake levels, aquifers, and the environment as a whole. Therefore, it is vital to learn about and protect our water resources.

When we talk about the water cycle moving water vapor in and out of the atmosphere, there are no human activities that can affect that. Water vapor will still evaporate into the atmosphere whether the ground water is dirty or clean.

n. The cycle of evaporation and condensation that controls the distribution of the earth's water as it evaporates from bodies of water, condenses, precipitates, and returns to those bodies of water. Also called hydrological cycle

NOTE:might not be right...

1. Evaporation (from oceans etc) and transpiration (from vegetation).
2. Condensation, forming clouds.
3. Precipitation in the form of rain, snow, hail and sleet.
4. Run off (surface water, above ground), Underground water (infiltration, percolation), collection and storage.

Evaporation:

Evaporation is when the sun heats up water in rivers or lakes or the ocean and turns it into vapor or steam. The water vapor or steam leaves the river, lake or ocean and goes into the air. Transpiration is when the water moves out of leaves.

Condensation:

Water vapor in the air gets cold and changes back into liquid, forming clouds. This is called condensation.

You can see the same sort of thing at home... pour a glass of cold water on a hot day and watch what happens. Water forms on the outside of the glass. That water didn't somehow leak through the glass! It actually came from the air. Water vapor in the warm air, turns back into liquid when it touches the cold glass.

Precipitation:

Precipitation occurs when so much water has condensed that the air cannot hold it anymore. Sometimes this happens when winds blow clouds up the side of a mountain. The clouds get heavy and water falls back to the earth in the form of rain, hail, sleet or snow.

Collection:

When water falls back to earth as precipitation, it may fall back in the oceans, lakes or rivers or it may end up on land. When it ends up on land, it will either soak into the earth and become part of the "ground water" that plants and animals use to drink or it may run over the soil and collect in the oceans, lakes or rivers where the cycle starts all over again.

A:

1-Evaporation: Liquid H2O(water) is turned into gas form and rises into the atmosphere by having the energy in its molecules increased through heat and dryness in the lower atmosphere

2-Condensation: the evaporated H2O now is gaseous form rise into the atmosphere and cools off as it loses energy due to its ascent, the gas molecules exist as supercooled drizzle drops (real term) after reaching a cooling point. In this state they do not contain enough mass separately to fall back down. Other microscopic particles from dust or smoke make their way up high into the atmosphere as well to and give the gas molecules a surface on which to gather until they become too dense for the heat rising off of the earth to support as clouds.

3-Precipitation:The condensed H2O molecules bond together due to surface tension in the now formed raindrop, if the atmospshere is colder they can form snowflakes or hail.

4-Runoff: The precipitated H2O collects in reservoirs to be re-evaporated. Precipitated water runs downs streets and through rivers collecting into larger and larger basins each time until the lowest spots are filled (the oceans and lakes) Special situations also exist in this category concerning irrigation, snow collection and melt, sublimation (where the H20 turns from a solid to a liquid immediately skipping the liquid phase).

Nine Steps:

evaporation--->transpiration--->condensation--->precipitation--->runoff--->percolation--->groundwater--->sublimation--->accumulation

? The general consensus of scientists and historians is that the discovery of the "water cycle" took place in 1582. This discovery is attributed to the Frenchman, Bernard Palissy, who wrote about the water cycle in his book, Discours Admirables

.

In this book, Palissy clears up previous misunderstandings by documenting his observations of water in nature, and stating that rain and melting snow were the only sources from which springs and rivers derived their waters:

“When I had long and closely examined the source of the springs of natural fountains, and the place whence they could come, I finally understood that they could not come from or be produced by anything but rains. (Palissy, 1957, p. 48)

Palissy gave us the first clear definition of the water cycle and its relative parts of evaporation, condensation, precipitation, ground infiltration, surface run-off and ground- water storage and flow toward the surface in rivers and springs.

An important aspect of Palissy’s water cycle observations is his keen understanding of cycles in nature, and his writings about the discontinuity between rainfall and river flow, with confused previous scholars. In Palissy’s words:

“… rain water that falls on mountains, lands, and all places that slope towards rivers or fountains, do not get to them so very quickly. For if it were so, all fountains would go dry in summer: but because the waters that fell on the land in winter cannot flow quickly, but sink little by little until they have found the ground floored by something, and when they have found rock they follow its slope, going into the rivers. From this

it follows that under these rivers there are many continual springs, and in this way, not being able to flow except little by little, all springs are fed from the end of one winter to the next. (Palissy, 1957, p. 68)

About one-hundred years after Palissy’s discovery of the water cycle definition, renowned scientist, Edmund Halley, as well as other scientists, confirmed Palissy’s definition as being accurate.

Thus, we can say, with reasonable accuracy, that Bernard Palissy’s discovery and definition of the water cycle is the definition that has been taught for over 430 years.

The clouds floating overhead contain water vapor and cloud droplets, which are small drops.