HYDROLOGY

Presented by

Vijay Marcel D

II M.Tech (RE)

Regno:113012301005

Hydrology

• Hydrology deals with the distribution of water on

land beneath the surface of earth.

• It deals with the various condition which bring about

the transformation of water in one form or another.

The hydrological cycle

precipitation

atmosphere

interception

evapotranspiration

overland flow

infiltration

soil store

through flowpercolation

groundwater store

groundwater flowreturn flow

channel store

channel flow

surface store (lake)

surface store (ground)

evaporation

surface store (sea)

evaporation

The hydrological cycle

• The hydrologic cycle is the transfer of moisture from the sea to land and back to sea.

• The hydrologic equation is expressed as P=R+E

Where P is precipitation

R is Run-off

E is Evaporation

Definition

• Precipitation:

It includes all the water that falls from the atmosphere

to the earth surface.

• Run-Off:

It is the portion of precipitation which makes its way

towards streams, lakes and ocean.

• Evaporation:

It is the transfer of water from liquid to vapor state

Hydrograph

• It is the graphical representation between discharge

through the river and time.

• It has a rising limb, peak and receding limb in the

curve.

• It is plotted for several months to indicate the power

available from the stream at different times of day,

week or year.

Flow duration curve

• It is plotted between flow

available during a period

and the fraction of time.

• From this graph, the total

power available at the site

during that period is

known.

Mass Curve

• It is a plot between

cumulative volume of

water that can be stored

from the stream and time.

• If the curve is steep the

river flow is large and if the

curve is flat the river flow

is small.

Run-off Estimation• The Run-off estimation is calculated by the formula

R= K.A.P

Where,

R is the run-off in hectare

A is the area of catchment in hectare

P is the precipitation in cm

K is the co-efficient taking losses into account.

• It is also estimated from the hydrograph.

Factors affecting Run-off

• The factors affecting run-off are

– Precipitation characteristics

– Meteorological characteristics

– Catchment characteristics

– Storage characteristics

• Precipitation characteristics include the intensity,

extent and duration of storm.

Factors affecting Run-off

• Meteorological characteristics include temperature,

humidity, wind, pressure variation, etc.

• Catchment characteristics include the size, shape and

location of catchment produce the significant effect

on the run-off.

• The types of catchment shape are fan shaped and fern

shaped.

Picture: Catchment area of River Cauvery

Source: Integrated hydrological data book, Central water commission

• In the fan shaped catchment, water from the tributary

simultaneously join the main river creating a sudden rise

of discharge and the chances of flood increases.

• In fern shaped, the tributary is distributed evenly it takes

different point of time to reach the main river so as to

cause any flood is minimal.

• For example the catchment area of river Cauvery in

Karnataka is fan shaped and the catchment area in

Tamil Nadu is fern or leaf shaped*

• Storage characteristics: It is the part of precipitation that

is stored within an area in lakes, ponds and tanks

temporarily or permanently.

* Water resources information system of India

Thank you

Regards

Vijay Marcel D

II M.Tech(RE)