Presentation is about Hydrological Cycle and is part of courses such as Hydrology, Groundwater Hydrology

1. HYDROLOGY
UG Subject: CET304
L02: Hydrological Cycle
By
Rohit Goyal, Prof., Civil Engineering (rgoyal.ce@mnit.ac.in)
0

2. 1
What is covered
Earth’s Water Cycle
Primary forces driving this cycle
Various quantities and water balance
Systems concept
Components of Hydrological Cycle
Human impact on Hydrological Cycle

3. 2
Percolation

4. 3
Comments
• Hydrological cycle is a continuous process by which water
moves through the Earth's systems
• Therefore, water is a renewable resource
• Is it importance for sustaining life and ecosystems???

5. 4
•What drives the hydrological cycle?
•How?

6. 5
The Hydrological Cycle: Earth's Water Cycle

7. 6
Primary forces driving - Water Cycle
• The hydrological cycle is primarily driven by
• Solar energy
• Gravity
• These two forces work together to move water through its various
phases and processes in the cycle.
• Energy powers the processes of evaporation and transpiration. Sun also plays
a crucial role in warming the Earth's surface, which influences weather
patterns and atmospheric circulation, affecting the distribution of water in the
atmosphere.
• Gravity plays a pivotal role in the downward movement of water. Gravity also
drives the processes of runoff and infiltration.

8. 7
The Hydrologic Cycle
Source: Chow, Maidement, Mays; Bedient
P
Runoff
Runoff
Evap
ET
Evap
Streams
Lake
Reservoir
GW
Atmospheric Moisture
100
Precipitation on land
Infiltration
Groundwater flow
1 Groundwater
discharge
38 Surface discharge
61
Evaporation from land
39
Moisture over land
385
Precipitation
on ocean
424
Evaporation
from ocean
Surface
runoff
Impervious
strata
Groundwater
Recharge
Precipitation
Snow
melt These
figures are
40-50
years old

9. 8
Source: Chow, Maidement, Mays
Important for mankind

10. 9
Source: Chow, Maidement, Mays
% Ocean % Land
70.8% 29.2%
79.4% 20.6%
87.5% 12.5%
95.3%
4.7%
100%

11. 10
Source: Chow, Maidement, Mays

12. 11
• Figures mentioned in different slides were derived about 45-50
years back. Is there latest data available in literature?
• Is data available for India?

13. 12
Components of the Hydrological Cycle
• Evaporation: Water from oceans, lakes, and rivers turns into water vapor
due to heat from the sun. Transpiration is water evaporating from plant
leaves. Evapotranspiration is sum of these two.
• Condensation: Water vapor rises and cools in the atmosphere, forming
clouds.
• Precipitation: Water droplets in clouds combine and fall back to Earth as
rain, snow, sleet, or hail.
• Infiltration: Some precipitation seeps into the ground, increasing soil
moisture of plants root zone. Deep percolation is water moving downward
to groundwater.
• Runoff: Excess water flows over the land and returns to rivers, lakes, and
oceans.

14. 13
• Factors affecting evapotranspiration?
• Temperature
• Humidity
• Wind
• The level of the plant’s growth etc.
• How to measure evapotranspiration?
• Lysimeter: A device used to measure
actual evapotranspiration.
• Field Experiment: Measuring the
amount of water used by a crop in a
field.
• Soil Moisture Depletion Study:
Measuring the amount of water used by
a crop
• Water Balance Method: A method that
involves measuring the amount of water
that enters and leaves a field.

15. 14
• How to
measure
Precipitation?
• Raingauge
s
• Earlier they
were mostly
manual
collection of
collected water
daily or hourly
• Now automatic
records exists
– e.g. tippling
bucket type

16. 15
•What is the shape of a raindrop?

17. 16
Shape of a Raindrop
• A common misconception is that when raindrops fall,
they have a teardrop shape.
• Smaller raindrops (1 millimeter) are almost perfectly
spherical.
• Larger raindrops (2-3 millimeters across) are also
round, but with a small indent on their bottom side.
• They look more like kidney beans when falling.
• Very large rain drops (larger than 4.5 millimeters) have
a huge indent and look more like a parachute.
• These extra-large drops usually end up splitting into two
smaller droplets. The indents on raindrops are caused by air
resistance.
Source: Precipitation (nationalgeographic.org)
https://www.baranidesign.com/faq-
articles/2020/1/19/rain-gauge-accuracy-and-
wmonws-standards

18. 17
• Infiltration is the process by
which water on the ground
surface enters the soil
• The infiltration capacity is
defined as the maximum rate
of infiltration
• Infiltration depends upon
• Soil characteristics
• Soil moisture content
(Antecedent Moisture
Condition, AMC)
• Land cover
• Slope

19. 18

20. 19
Surface runoff shortly after a precipitation event of 15 mm (in
40 min) in the Lake Manyara region (2013-03-16; photo G.
Quénéhervé).
Runoff occurs when excess
rainwater can no longer rapidly
infiltrate in the soil
https://www.researchgate.net/publication/281624420_Site_effects_associated_with_the_2010_maule_earthquake_in_zones_characterized_by_the_p
resence_of_wetlands_in_the_Biobio_region_Chile/figures?lo=1
• The land area producing
runoff that drains to a
common point is called a
drainage basin
• Factors affecting runoff are
• Precipitation
• Topography of drainage
basin
• Land use-landcover
• Soil
• Slope
• Weather
• Runoff causes erosion and
deposition and flooding

21. 20
Human Impact on the Hydrological Cycle
• Study of large number of water bodies have concluded that seasonal
variability in human-managed reservoirs averaged 0.86 metre,
compared with 0.22 metre in natural water bodies.
• Vast usage of chemicals, pesticides, fertilizers and pollutants causes
eutrophication.
• Eutrophication is growth of algae due to excess nutrients in lakes, pond and
rivers.

22. 21

23. 22
Summary
• Water is continuously moving in cycle and thus sustaining life
• There are many processes such as precipitation,
evapotranspiration, infiltration, runoff, which are continuously
moving water from one phase to another
• We could model all such processes systematically and can
understand the different processes and factors affecting them
• Still humans are influencing hydrological cycle and changing
both quantities and quality of water in local, regional and
global hydrological cycle.

24. 23
Let us take a pledge
•We, as an engineers and knowledgeable
members of the society, have a great
responsibility to
• Conserve water
• Preserve water quality
• Contribute to the society efforts to bring clean
water to every human being

25. THANK YOU
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