How streams are classified? The most popular measurable terms classifying the flowing water body into "the stream order" are discussed in this presentation. .

1. Stream Order
Dr. Surjya Kumar Saikia
Department of Zoology
Visva-Bharati

2. Physical Methods
• Stream order is a measure of the
relative size of streams.
• Range from smallest, first-order,
to the largest, the twelfth-
order(Amazon)
• Over 80% of total length of
Earth’s rivers and Streams are
headwater streams(first and
second order)

3. • As water travels from
source to mouth, the
streams tend to increase
in width, depth, and
discharge.

4. First order streams
• Perennial: carry water
all year
• Smallest streams
• Have no permanently
flowing tributaries

5. Second Order Streams
• Two first order
streams come together
to form one second
order streams.
• However, if a first
order stream joins a
second order, it is still
a second order

6. Third Order Stream
• When two second
order streams come
together, it forms a
third order stream.
• How has the width of
the stream changed
since it was 2nd order?
How about since 1st
order?

7. Fourth Order Stream
• When 2 third order
streams come
together,it forms a
fourth order stream
• How has the width and
canopy changed since
1st, 2nd, and 3rd order
stream?

8. Stream order
• Two of the same order
streams must come
together before that
stream goes up one
level.

9. Stream Ordering
Headwater (1-3)
Mid reach
(4-6)
Lower reach (>6)

10. 4 - 6
1 - 3
> 6
STREAM ORDER
Headwaters
Midreach
Lower
Reaches

11. Types of organic matter
• Particulate organic matter
–CPOM-Coarse particulate organic matter
• Woody material & leaves (> 1 mm)
–FPOM-Fine particulate organic matter
• Leaf fragments, invertebrate feces, and
organic precipitates (50um – 1 mm)
– Ultrafine (UPOM)
• Even smaller fragments (0.5 – 50um)

12. Types of organic matter
• DOM- Dissolved organic matter
– Soluble organic compounds (<0.5 um) that leach
from leaves, roots, decaying organisms, and other
terrestrial sources
– Microbial sources: algal exudates, senescent
bacteria
– 50% is humic material- HDOM
– Largest pool of organic matter in streams

13. Dynamic Equilibrium
• Stream forms equilibrium between physical
parameters (width, depth, velocity, and sediment load, both means
and extremes) and biological factors
– SEASONAL: Uniform energy processing over
time; different species exploit different available
organic substrates as efficiently as possible
– SPATIAL: Energy loss from upstream = energy
gain/income for downstream

14. Energy Sources- Headwaters
• Shading: Riparian vegetation, limits
light to stream, low autotrophic
production
• Photosynthesis/Respiration (P/R) ratio
will be less than 1 (heterotrophic
stream)
• Lots of CPOM: allochthonous
carbon/energy sources (leaves from
watershed)
• Low temperture

15. Energy Sources- Midreach
• Stream broadening, more light
• P/R > 1, autotrophic production
(phytoplankton, periphyton, macrophytes)
• More FPOM, b/c CPOM
processed upstream
• Energy source is autochthonous.
• High temp variation

16. Energy Sources- Lower Reaches
• Increasing turbidity, even
wider stream, increased
macrophytes
• P/R < 1, net heterotrophic
• Mostly FPOM (vs. CPOM
in the headwaters)
• High phytoplankton, not
enough to cause the river
to become autotrophic
• Large volume, low temp

18. Connections from
upstream to downstream
habitats control flow of
energy and carbon in
fluvial ecosystems, as
well as the species of
aquatic organisms
River Continuum Concept: Vannote et al. 1980
Theme: importance of
light availability in
controlling in situ
production (e.g. P/R)

19. 4 - 6
1 - 3
> 6
STREAM ORDER
River Continuum Concept- BENTHIC INVERTEBRATES
CPOM
CPOM
CPOM
FPOM
FPOM
FPOM
Collectors
Shredders
Scrapers/Grazers
Collectors
Collectors
TESTABLE HYPOTHESIS- Taxonomy is the tool to measure this

21. RCC and Fish Communities
• Headwaters: cool water species (e.g., trout)
• Lower reaches: warm water species (e.g., carp)
• Most headwater fishes feed on invertebrates
• Mid to lower reaches, piscivorous species are also
abundant
• Lower reaches, planktivorous species may be present

24. Construction of a dam
changes the means and
extremes to which the stream
biota are adapted
Construction of a dam can
correspond to a “resetting” of
the river continuum, by
trapping material and making
sunlight more available to
support autotrophic growth.

25. What we have learnt………
• How to name and count river order
• The river continuum concept (RCC) and its
features
• Change in biota and physical features across
the stream orders