Hydrology – Introduction

Hydrology is study of science of water It deals with depletion and  replenishment of water resources of the earth. Hydrology deals with the occurrence, movement, distribution and circulation of water whether above the ground, below the ground or in the atmosphere


Object & Applications of Hydrology

The main object of hydrology is to estimate yield from drainage basin. It is the calculation related to the precipitation, losses and runoff within the catchment area.




Applications of hydrology system are

  • Design of hydraulic structures
  • Irrigation
  • Hydro-power
  • Flood control and management
  • Municipal & Industrial water supply
  • Pollution control
  • Navigation
  • Draught Management


Some facts about world’s water resources


Total available water – 1380 Million Cubic km

Saline water – 97.2%

Fresh Water – 2.8%

Fresh water is further divided in

  • 2.15% – Glaciers at polar caps
  • 0.32% – Ground water
  • 0.33% – Available for human consumption

Water for Human use = (0.33*1380)/100 = 4.5 M Cubic Km

World’s Average Annual precipitation – 100 cm

India’s Average Annual Precipitation – 119.4 cm


Hydrological Cycle –


 The stages of hydrological cycle are
  • Precipitation – It is each type of moisture reaching ground from atmosphere.
  • Evaporation – water from storages vaporising due to heat of sun
  • Transpiration – process of water leaving plant through leaves and diffuse into atmosphere as vapour
  • Evapotranspiration – sum of plant evaporation and land evaporation
  • Infiltration – process by which water gets into the surface strata of earth to meet soil moisture deficiency
  • Runoff – portion oof rain that ultimately joins the streams, rivers or any water body.





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