Without Water there would be no life, Water effects all ecological systems. Two thirds of the earth is covered in water.
Human usage includes drinking water, irrigation for food production, cleaning, clean energy production using dams and now tidal energy
Dangers exist from too much or too little water, flooding, famine due to drought, tsunamis.
Since the beginning of human history wars are fought over control of drinking water,over oasis, wells, streams and rivers.
National political tensions are rising as rivers are diverted and large areas are flooded by dam building.
Technology can help in desalination of sea water
Nanotechnology for desalination
enhancing water quality
search for water on the moon and other planets.
Roughly 70 percent of worldwide water use goes to food production, which is implicated in groundwater depletion and ecologically destructive freshwater consumption from California to the Indo-Gangetic Plain to Central Asia to northern China.