Water


Water is a tasteless, odorless, and nearly colorless substance in its pure form that is essential to all known forms of life and is known also as the most worldwide solvent. Water is a plentiful essence on Earth. It exists in many places and forms: mostly in the oceans and polar ice caps, but also as clouds, rain water, rivers, freshwater aquifers, and
sea ice. On the planet, water is always moving through the cycle linking vanishing, rainfall, and runoff to the sea.
Water that humans consume is called potable water. This natural resource is becoming scarcer in certain places as human population in those places increases, and its availability is a major social and economic concern.

A surprising substance
Changing appearances
Drinking water for more details on this topic, see Category: Forms of water.
Water takes many different shapes on earth: water vapor and clouds in the sky, waves and icebergs in the sea, glaciers in the mountain, aquifers in the ground, to name but a few. Through evaporation, precipitation, and runoff, water is constantly flowing from one form to another, in what is called the water cycle.
Because of the value of precipitation to agriculture, and to mankind in general, we give different names to its various forms: while rain is common in most countries, other phenomena are quite surprising when seen for the first time: hail, snow, fog or dew for example. When properly lit, water drops in the air can refract sunlight to create rainbows.
Similarly, water runoffs have played main roles in human history: rivers and irrigation brought the water needed for agriculture. Rivers and the seas offered prospect for travel and commerce. Through erosion, runoffs played a major part in shaping our environment provided that river valleys and deltas which provide rich soil and level ground for the enterprise of population centers.
Water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs or more outstandingly in hot springs and geysers. Groundwater is also extracted unnaturally in wells.