Water is a precious natural resource vital, for sustaining all life on the earth. It is in a continuous circulatory movement between land, ocean and atmosphere - the hydrological cycle. It is not uniformly distributed in time and space. Due to its multiple benefits and the problems created by its excesses, shortages and quality deterioration, water as a resource requires special attention.		Fig: Hydrological Cycle Source : Irrigation Theory and Practices: Michael
Sustainable development demands that we should use our precious water resources efficiently and effectively. This will have to include forward planning and action, which can specifically address; both, the existing and emerging human and environment problems. On a global scale, total quantity of water available is about 1600 million cubic km. The hydrological cycle moves enormous quantities of water about the globe. However, much of the world's water has little potential for human use.

The distribution of water on earth in percentage is estimated as below:

Oceans                                      97
Ice-Caps                                    02.0
Ground water                              0.62
Fresh Water lakes                        0.009
Inland sea and salt lakes               0.008
Atmosphere                                0.001
Rivers                                        0.0001
Total                                         99.6%(aprox)
 

Hence, the fresh water resources of an area comprise mainly of:

• Surface water resources (rivers, lakes, ponds, etc.).

• Groundwater resources.
  
  In view of limited water availability one can appreciate the wisdom of ancient people in formulating codes and norms for protecting water bodies.

The Water Budget:

India has sizable resources of water and a large cultivable land but also a large and growing population to feed. Erratic distribution of rainfall in time and space leads to conditions of floods and droughts which may sometimes occur in the same region in the same year. India has about 16% of the world population as compared to only 4% of average annual runoff in the rivers.