2. Dimensions of river ecosystems
• Longitudinal
• Lateral
• Vertical
• Temporal
2
3. Longitudinal Changes in Streams
• Certain
characteristics of
streams change
predictably from
upstream to
downsteam
– Channels become
wider
– Flow becomes
slower, but greater
in volume
– Streams become
deeper
3
4. Longitudinal Changes
– Reach Scale
• Longitudinal changes are
also observed at shorter
scales than the entire
river length
• We call this shorter scale
the “reach” scale
• One example of reach
scale changes is the pool-
riffle pattern found in
many streams draining
areas with medium
gradient
• Riffle is an area of rapid
flow over coarse substrate
(rocks) whereas the pool
is a slower flowing stretch
with finer substrate
• Path of flow - thalweg
4
5. Lateral Patterns
• There are also some
predictable changes
laterally
• The stream has a low
flow channel; the fastest
flow is called the
thalweg
• The stream has banks
which define its frequent
flow limit
• The stream has a
floodplain which defines
its flow limit on less
frequent events, annual
or lesser frequency
5
6. Lateral Patterns
• Some streams
and rivers will
have a single
dominant
channel while
others will
have a
network of
interwoven
channels
6
7. Lateral Features
• As rivers
increase in
size they
may develop
a complex
floodplain
system
7
8. Vertical dimensions
• Velocity changes with depth in stream channel
• Discharge (Q) = VA
Diagram by:Eric G. Paterson
Department of Mechanical and Nuclear Engineering
The Pennsylvania State University
8
10. Lateral and Vertical Patterns
• In many large
alluvial valleys,
creatures that live
in ground water
and hyporheic
water can be
found in the
subsurface water
kilometers from
the stream. In
other words the
stream extends
well beyond its
channel.
10
11. Temporal dimension
• Stream flow changes
Second by second
Hourly
Daily
Monthly
Seasonally
Annually
Milleniumly
11
12. Selected Important Habitat Factors
• Substrate
• Temperature
• Oxygen levels
• Flow velocity
• Food availability
• pH
• Nutrient and sediment regimes
• Organic input and transport
12
13. How are species distributed in
space and time?
-- Environments contributing to riverine
biodiversity
Surface water Subsurface water Riparian system
Streams
Springs
Lakes
Hyporheic
Zone
Ground
Water
Confined
Reaches
Unconfined
Reaches
13
14. River --------------------------------------------- Floodplain Edge
Spatial distribution of species across a
floodplain (lateral dimension)
Species Richness
0
50
100
Percent
of
maximum
richness
fish
Mollusca
Odonata
Amphibia
Macrophytes
(Ward and Tockner 2001 fig. 9.3)
Species Richness
0
100
Eg.
Fish
Snails, slugs, mussels,
Dragonflies, damselflies
Frogs, salamanders, toads
Aquatic plants
14
16. Human caused disturbances
• Agriculture
• Timber harvest
• Mining
• Urbanization
• Introduction of exotic species
• Harvesting of fish and wildlife
16
17. Land use/cover
and vegetation
Physiography Climate
Landscape controls
Nutrient
Inputs
Solar energy
and
Organic input
Regime
Gross reach
morphology
Habitat Forming
Processes
Species assemblages
Stream
Morphology and
Conditions
Biodiversity
Habitat complexes and conditions
e.g., pools, riffles, temperature, etc.
Sediment
and Hydrologic
Regime
Modified from Roni et al. 2002.
17
18. Physical, chemical, and biological
components related to water quality
• Light
• Temperature
• Dissolved ions
• Suspended solids
• Nutrients and gases
• Toxics such as metals and pesticides/herbicides
• Biological features
• PPCPs (Pharmaceuticals & Personal Care Products)
18
19. Photos by R.S. Lindsay
Photo by Carrie Inman
Agriculture
19
24. Large storage
in soil,
channel and
valley floor Recharge
Natural
cleaning
Pollutant
wash off
No recharge
Rapid flow
limited storage
Natural Developed
Reduced soil storage
Limited infiltration
Precipitation
24
26. How do we manage watershed?
• Dept of Natural Resources Regulations
• U.S. Forest Service Regulations
• Clean water act
• Endangered Species Act
• Total Maximum Daily Loads (TMDLs)
26
30. Take Home Messages
• Understand the interactions between land
use/land cover and components of the
hydrologic cycle
• Be able to describe what is typically
measured in watersheds and why
30
31. Hydrology Report
~ 2-3 pages due May 25 individually
Include:
Name, Date, Title
Introduction
Methods
Results and Discussion (w tables)
Conclusions
Appendix (if needed for raw calculations)
31
