• Two Greek Words:
– “Hydor” means Water and
– “Logos” means knowledge.
Some Definitions of Hydrology
• The science encompassing the behavior of water as it occurs in the
atmosphere, on the surface of the ground, and underground. (Am. Soc.
Civil Engineers, 1949, p. 1.)
• The science that relates to the water of the earth. (Meinzer, 1923, p. 9.)
• The science treating of the waters of the earth, their
occurrence, distribution, and movements. (Jarvis and others, 1936, p.
[Source: http://water.usgs.gov/wsc/glossary.html#H ]
• The applied science concerned with the waters of the earth, their
occurrences, distribution, and circulation through the unending
hydrologic cycle of: precipitation, consequent
runoff, infiltration, and storage; eventual evaporation; and so forth.
It is concerned with the physical and chemical reaction of water
with the rest of the earth, and its relation to the life of the earth.
[Source: http://www.nws.noaa.gov/om/hod/SHManual/SHMan014_glossary.htm ]
According to , Wisler and Brater
Hydrology is a science
• Processes governing water depletion and
replenishment on land.
• transportation of water through the air, over
the ground surface and through the strata of
• various phases of the hydrologic cycle.
Humans first settled along the banks of
lakes and rivers,
Due to Proper Management of Water
canals, levees, dams, subsurface water
conduits, and wells were created during
The flow rates and yields of rivers were
monitored by the Egyptians.
As early as 3800 years ago,
Rainfall measuring instruments were first
utilizedKautilya of India About 2800 years ago,
Global hydrologic cycle dates back At least 3000 years
The Romans developed aqueduct systems
The waters in rivers come from precipitation. At least 3000 years
The modern scientific approach to studying the
hydrologic cycle was initiated.
During the 17 century
Mathematics, fluid mechanics, and hydraulics During 18 century
The term “hydrology” arrived in its current meaning During 1750
Water Transport in Porous media, ground water
flow, sediment and more technical fact about
First formal recognitions of the scientific status of
Many new breakthroughs in the hydrological
sciences are eminent
During 21 century
• Does it covers all studies of ocean water????
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