Introduction to Water Supply

Water
Water Is a commonly available chemical substance on earth, which is essential for all known forms of life, In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71% of the Earth’s surface. On Earth, it is found mostly in oceans and other large water bodies, with 1.6% of water.b1ow ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air, and precipitation. Oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%. A very small amount of the Earth’s water is contained within biological bodies and manufactured products.
Clean, fresh drinking water is essential to human and other life forms. Access to safe drinking water has improved steadily and substantially over the ‘last decades in almost every part of the world. However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. A recent report (November 2009) suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50%.
Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70% of freshwater is consumed by agriculture.

Movement of Water in Nature

Water on Earth moves continually though a cycle of evaporation or transpiration (evapo-transpiration), precipitation, and runoff, usually reaching the sea. Most of the earth’s water sources get their water supplies from precipitation, which may tall in various forms, such as rain, snow, hail, dew etc. Rains, no doubt form the major part of the supplies. Since the precipitation is the principal source of water on the earth, It is worthwhile to study the overall hydrologic phenomenon of movement of water, which described by the Hydrologic cycle. Unlike other commodities, water is not manufactured. Instead it is continuously re-cycled naturally through many different forms. This cycle, called the hydrological cycle, involves evaporation, transpiration, evopo-transpiration, condensation, precipitation, infiltration, percolation and runoff.
An understanding of hydrological cycle helps to explain the way in which all water becomes available.