eh l01 introduction
TRANSCRIPT
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LECTURE 1INTRODUCTION
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At the end of the week, students should be able to:
descr ibe and exp lain the hyd rolog ic cycle
and i ts component .
state and app ly the water budget equation.
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1.0 DEFINITION OF
HYDROLOGYHydrology is the earth science which deals withwater in all its natural forms as it occurs on theearth.
It includes occurrence, distribution, movement
and properties of water of the earth.It requires the knowledge of many naturalsciences, including hydraulics, physics,meteorology, chemistry, mathematics and
geology.Hydrology can be classified into : Scientific Hydrology
Engineering Hydrology
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1.1 Definition Of
Engineering Hydrology
Engineering hydrology is a civil engineering
discipline, utilizes hydrologic data such as
precipitation, streamflow and evaporation in the
planning, design and operation of engineeringprojects for the control and use of water.
Analysis techniques in this field focus on
determining the magnitude and frequency of
hydrologic events such as storms, flood flows,droughts and low flows.
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1.2 Availability OF World Water Resourses
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1.3 Hydrologic Cycle
Continuous, unsteady circulation of water from theatmosphere to and under the land surface andback to the atmosphere by various processes.
Temporal variations may occur in the atmosphere,on land surface, in surface waters and in thegroundwater of an area.
No beginning or end.
Water may appear in all three of its states : solid,liquid, and gas
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Hydrological Cycle
Ocean
EvaporationEvaporation (ET)
runoff
Precipitation
Aquifer
Infiltration
Evaporation
Precipitation
Evaporation/ET
Surface Water
Groundwater
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Precipi tat ion
General term used to describe water whichcomes to earth in the form of rain, hail, snow anddew.
Occur as rain as a driving force providing waterin the environment
Annual amounts of precipitation areunpredictable and variable, approximately in the
range of 1500-4000 mm in various locations inMalaysia.
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Inf i l t rat ion
Passage of water through air-soil interface
Affected by factors such as time, soil porosity,
permeability, antecedent soil moisture conditionsand presence of vegetation.
Urbanisation will decreases infiltration with a
resulting increase in runoff volume anddischarge.
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Evaporat ion and Transp irat ion
Evaporation is the process whereby water is
transformed from the liquid or solid state into the
gaseous phase by the transfer of heat energy.
Measured as a rate of mm/day or mm/year.Transpiration is the mechanism whereby water
moves up through vegetation into atmosphere
and subsequently evaporated. Measured as a
rate of mm/day or mm/year.
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Evapotranspiration is used to describe the
quantity of water used by plants in transpiration
together with the water evaporated from the
adjacent soil or intercepted precipitation.Its rate affected by temperature, wind, vapour
pressure, plant characteristics and availability of
soil moisture.
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Surface Runoff
Refer as overland flow
Process whereby water moves from the ground
surface to a water way or water body.
Affected by precipitation, infiltration,imperviousness and land slope.
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Interf low
Refer as subsurface stormflow
Process whereby water moves laterally
beneath the land surface but above
groundwater table.
Considered part of the surface runoff.
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Groundwater f low
Refer as baseflow whereby water move
laterally beneath the water table toward
and into a waterway or water body.
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1.4 Catchment Characteristics
Catchment/WatershedAreaconsist of area of
land that draining water into a stream or a water
course during a rainstorm to the outlet at a given
location.Catchment Dividedelineate a catchment from
its neighbouring catchment area.
Catchment Lengthdistance measured along
main channel from the watershed outlet to the
basin divide.
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Catchment Sloperate of change of
elevation with respect to distance along
the principal flow path.
L
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1.5 Water Budget Equation
Continuity Equation for water in its various phases is
given as
Mass inf low - Mass ou tf low = Change in m ass storage
SOI
Since all term in hydrological water budget may not
at the same degree of accuracy, Water Budget
Equation for a catchment at a time interval t is
written as
STEGRP
if all density are the same