Estuaries are coastal bodies of water where freshwater from rivers meets and mixes with saltwater from the sea. They exist in a transitional zone where tidal effects and freshwater inputs influence the environment. Estuaries come in different forms depending on their geological origin and range from coastal plain and bar-built systems to tectonic and fjord-type estuaries. India has many economically and ecologically important estuaries located mainly along its eastern coastline that are threatened by pollution, development, and other human impacts.

2. Estuaries- where river meets the sea
 Latin origin-”AESTUS”-Tide.
 A semi-enclosed coastal bodies of water that have a free connection with the open sea and
within which sea water is measurably diluted by freshwater.
 It is strongly affected by tidal action & some of wave action.
 According to Perillo(1995) : "an estuary is a semi-enclosed coastal body of water that
extends to the effective limit of tidal influence, within which sea water entering from one or
more free connections with the open sea, or any other saline coastal body of water, is
significantly diluted with fresh water derived from land drainage, and can sustain
euryhaline biological species from either part or the whole of their life cycle."

3. “Wave
and
Tide
dominated
estuary
model.”

4. Coastal plain Bar-built Tectonic Fjord-type
Formed by rising
sea level during
interglacial period
eg. Delaware River
Deposition of
sediment and
formation of sandbars
eg .Great south bay
Earthquake cause
rapid sinking of
coastal areas below
sea level
eg San Francisco
Formed by glacial
Erosion during
warmer climate
period-coastal
fill the valley
eg. Alaska
Pritchard(1967)-Subdividedinto4 types on the Basis of origin

5. ←Delaware River
← Cape Hatteras
Coastal plain & Bar built Estuaries. Tectonic Estuaries.
Fjord type estuaries.

6. ←Delaware River
← Cape Hatteras
Coastal plain & Bar built Estuaries. Tectonic Estuaries.
Fjord type estuaries.

7. Basis on freshwater discharge/Salinity Condition
Positive estuary Negative estuary Neutral estuary
Freshwater dominates
over marine water
Marine water dominates
over fresh water
Relative constant in
relation to one another

8. ON THE BASIS OF CIRCULATION
 The water flow of river is
strongly dominant over tidal
action. So freshwater tends to
overflow the heavier salt water
forming a wedge.
 Characterized by the sharp
change in salinity from top to
bottom (Fig. 6).
 eg.-The Amazon river estuary
,the Nile river estuary
 River output is less than the
marine input
 Turbulence causes mixing of
the whole water column, such
that salt content varies both
horizontally and vertically
with moderate density
stratification.
 eg.--Chesapeake Bay
 The tidal action is
strongly dominant.
 The water tends to be
well mixed from top to
bottom and the salinity is
relatively high.
 eg- Bar-built estuaries.
Highly stratified Moderately stratified
Vertically/Completely
mixed

9. Major estuaries occur in the bay of
bengal. Many estuaries are locations
of some of the major seaports.
Most of the india’s major estuaries
occur on the east coast. In contrast,
the estuaries on the west coast are
smaller.
Two typical examples of estuaries on the
west coast are the mandovi and zuari
estuaries located to the north and south of
the main campus of the national institute of
oceanography at dona paula, goa.
Source: CSIR-NIO
ESTUARIES

11. Indian Coastal
States Estuaries
Avg. discharge
(m3/sec/day)
Gujarat
Ambica 1
Bhadar 16
Daman ganga 93
Dhatarwadi 2
Gulf of Kutch < 1
Machhundri 3
Madhuvanti 1
Mahi 383
Meghal 7
Narmada 190
Prabhas Patan 4
Sabarmati 33
Singoda 3
Tapi 210
Maharashtra
Daman ganga 93
Narmada 190
Karnataka
Karwar 128
Mandovi 56
Kerala Periar Estuary 8
Tamil Nadu
Cauvery 600
Ponnaiyar 21
Vaigai 28
Andhra Pradesh
Godavari 3, 500
Krishna 2, 100
Pennar 200
Odisha Mahanadi 2,100
West Bengal Ganges delta 35, 217
East coast West coast
West Bengal=1 Gujarat=14
Orissa=1 Maharashtra=2
Andra Pradesh=3 Karnataka=2
Tamil Nadu =3 Kerala=1
Total 8 19
Source:
Centre for Coastal Zone Management and Coastal
Shelter BeltHosted by Institute for Ocean
Management,Anna University Chennai
Sponsored by Ministry of Environment, Forests & Climate
Change, Govt of India

12. Estuaries
As
Ecosystem
Coping
With
Salinity
Fluctuations
Adapting
to
The
Mud
Clams extend
their siphons
for food and
oxygen
Problem::
• Nothing to hold on to
• Difficult to move on mud
• Depletion of oxygen
Benefit:
Salinity fluctuation is less
drastic

13.  Estuaries have been called the "nurseries of the sea".
 Important for the health of the oceans.
 Act as a buffer between the ocean and the land.
 Economically important. Coastal activities, commercial and
recreational fishing, boating, and tourism.
 A historical and cultural significance.

14. http://www.earthgauge.net/wp-content/images/Estuaries_Low.jpg

15. THREATS
 Excess silt flowing in from land clearance.
 Pollution from sewage, industrial wastes and agricultural run-off.
 Oil spills / oil spillage.
 Invasion by introduced species.
 Construction of harbours, channels, embankments and roads.
 Solid wastes, garbage, Liquid wastes disposal.
 Natural disasters (e.g. cyclone, earthquake)
 Conversion to mining, aquaculture, aquaculture, agriculture, salt pans, urban
development
 Over exploitation by traditional users.
 Different pests and diseases.
 Other hazardous chemicals.
 Lack of sustainable mangrove management etc.

16. HOW CAN WE
HELP TO PROTECT
OUR ESTUARIES

17.  Estuaries are a vital part of ecosystem. The huge amount of organisms living
in this environment are essential to the well being of other environments such
as the ocean and rivers.
 Essential to anadromous animals that travel up stream to spawn.
 They also act as the filter of the water travelling downstream towards the
ocean.
 Without estuaries, many species of plants and animals would not be able to
survive

18. BOOKS
Marine biology by Peter Castro, Michael E. Huber.
Biological oceanography : An introduction by Carol & parsons
WEBSITES
 https://oceanservice.noaa.gov/facts/estuary.html
 www.doc.govt.nz/nature/habitats/estuaries/about-estuaries/

19. Thank you for viewing.
We do not inherit the earth from our
ancestors, we borrow it from our
children. ~Native American Proverb