1. SEMINAR TOPIC
HYDROLOGY
PRESENTED BY:
PRASHANT S HIREMATH
BACHELOR OF ENGINEERING IN CIVIL
ENGINEERING
Smt. Kamala & Sri. Venkappam M. Agadi College of
Engineering & Technology Department of Civil
Engineering Lakshmeshwar – 582116
2020-2021
3. INTRODUCTION
HYDROLOGY
HYDRO:- WATER
LOGY :- SCIENCE
Hydrology: Study of the hydrologic cycle; occurrence,
distribution, movement, physical and chemical properties of waters
of the earth and their environmental relationships.
Study and practice of hydrology: Aids in explaining and
quantifying the occurrence of water on, under and over the earth's
surface.
Hydrologic Cycle
Earth’s water resources are in a state of continuous circulation
linking the atmosphere, land and the oceans. This endless process,
which is powered by the forces of nature is called the Hydrologic
Cycle.
It is the basic framework upon which the science of hydrology is
built.
There are many processes that constitute the hydrologic cycle.
5. Global annual water balance
Ocean Land
Area (km
2
) 361300000 148800000
Precipitation (km
3
/yr) 458000 119000
(mm/yr) 1270 800
Evaporation (km
3
/yr) 505000 72000
(mm/yr) 1400 484
Runoff to ocean
Rivers (km
3
/yr) - 44700
Groundwater (km
3
/yr) - 2200
Total runoff (km
3
/yr) - 47000
(mm/yr) - 316
6. Precipitation
As the air continues to rise, the air cools at the wet lapse rate,
causing precipitation to form because the colder air can not
hold the excess moisture.
The condensing water generates heat, causing the air to warm
slightly, so that the wet air lapse rate is less than the dry rate.
The excess heat generated by the condensing water causes the
air to rise faster (because warmer air rises through colder air).
Three primary steps for formation of
precipitation:
Creation of saturation conditions in the atmosphere (typically
some type of lifting of air).
Phase change from vapor to liquid (cloud formation).
Growth of droplets to precipitable size (able to overcome
upward velocity).
7. Lifting Mechanisms
Front: The boundary between two adjacent air masses of
different temperature and moisture content.
Warm Front: Warm air advancing on colder air.
Cold front: Cold air advancing on warm air.
Measurement of Precipitation
Measured as a depth of water on a flat level surface if all the
precipitation remained where it had fallen
Units: inch, mm
Non Recording Gauge
8. US Standard Weather Bureau Gauge,
Diameter, Φ = 8 in (20.32 cm)
Area of the tube is 0.1 that of the funnel
Graduated Scale: To measure precipitation
Excess: Overtops the inner tube and collects in the
overflow can
Rainfall is measured by an observer at regular intervals
Recording Gauge
Tipping Bucket Gauge
9. Consists of a pair of buckets pivoted under a funnel
When one bucket receives 0,25 mm (0.01 in) of precipitation it
tips, discharging its content into the bucket, bringing the other
bucket under the funnel
Recording mechanism: Time of occurrence of each tip
measures rainfall intensity for short periods
