Envis Centre, Ministry of Environment & Forest, Govt. of India

Printed Date: Monday, June 24, 2024



Water Cycle

"Water is probably the only natural resource to touch all aspects of human civilization - from agricultural and industrial development to the cultural and religious values embedded in society."

When Neil Armstrong saw the Earth from the Moon, it appeared blue! This is because water covers more than two-thirds of the Earth's surface. But fresh water represents less than 0.5% of the total water on Earth. The rest is either in the form of seawater or locked up in icecaps or the soil, which is why one often hears of water scarcity in many areas.

Water is continuously moving around the earth and constantly changing its form. It evaporates from land and water bodies and is also produced by all forms of life on Earth. This water vapour moves through the atmosphere, condenses to form clouds and precipitates as rain and snow. In time, the water returns to where it came from, and the process begins all over again. Although water is constantly moving, its total quantity on Earth's surface is constant.

Water is essential for survival and is getting increasingly scarce to get day by day. Most of it constantly moves (some water stored as Ice in the Arctic may be there for as long as 200,000 years) through one of the most important of the biogeochemical cycles- the water cycle. While this cycle provides all of the earths fresh water, it also acts as a giant purification system becomes when it evaporates the pollutants do not go with it. Altogether there are about 1400 million cubic meters of water on this earth. 97% of it is sea water and 3% is fresh water. Out of the fresh water 77% is stored in the ice caps and glaciers, about 22% is ground water and 0.035 is atmosphere water vapour. Visible surface water in rivers and lakes accounts for on 0.33% of all fresh water. A mere spoon full, if all the worlds water is trapped in one litre bottle.

The water cycle starts with evaporation. Out of the 135000000 km3 of sea water, about 445000 km3 evaporates every year along with 71,000 km3 of surface water from the land. Falling eventually as rain or snow, it reaches the land and sea in different proportions. The land mass of the continents receive 104,000 km3 of water and only 412,000 km3 returns to the sea. The extra 33,000 km3 which falls on the land eventually runs back to the sea but in the meantime it satiates the water requirements of billons of people on this earth.



  • Diarrhoea
  • Hepatitis
  • Roundworm
  • Hookworm infection
  • Trachoma
  • Guinea worm
  • Schistosomiasis
  • Leishmaniasis
  • Lymphatic filariasis


An IGIDR study reveals that a combined initial capital investment of Rs. 6128 to 7353.6 crore and about 12,255 acres of land would be required to treat wastewater using ASTP be required to treat wastewater using ASTP technology in 3696 /towns in the country. Oxidation pond technology on the other hand would be a cheaper option at a capital investment of only Rs. 1838 crores, but the land requirement would be 61,280 acres. Much of which would have to be urban or town lands.




Land required

Capital costs
Lakh rupees/mld

Operation & maintenance costs
Lakh rupees/mld/year

Activated Sludge




Treatment Plant (ASTP)




Oxidation Ponds Aerated Lagoons




Upward Anaerobic Sludge Blanket (UASB)




Duckweed and fish culture technology




Karnal Technology




Trickling filter




Source: Ministry of Environment and Forests, 1998 






Although elaborate provisions of law appear to exist, the law remains ineffective and the environment continues to deteriorate. Experts from the National Law School of India University, Bangalore have evaluated the existing pollution control laws and suggested several reforms.

They suggest that the principal legislation is repetitious and poorly drafted. The laws are not backed by sound policy pronouncements and the legislation does not appear well through out but seem a hoc. This is especially true of a number of rules and notifications like the Coastal Regulation Zone and the Environment Impact Assessment notifications issued in recent times.

The pollution control laws are based on a command and control regime with an emphasis on punitive rather than pro-active and preventive measures. Though the boards have wide ranging powers, including the ability to hold industrialists personally liable for environment damage these are rarely exercised effectively. Undue emphasis is placed on criminal procedure, and as a result there is considerable delay in convictions. Before judicial process is initiated against polluters, spaces for cooperation and partnerships between various groups should be explored. Central and state boards also need powers to impose progressive monitory penalties on the polluters. This will, to a great extent, reduce need for time consuming legal recourse.

Greater cooperation between central and state pollution control boards is needed. Conflicts over jurisdiction between the state boards and the district administration should also be resolved for effective implementation of legal provisions.

Another major lacuna in the law is that some areas like groundwater pollution remain outside the purview of the pollution control laws. Consolidation and codification of the law would remove some of these problems.