**Course Title:** **Floodplain Management**

**Module 3:** Biological Landscape: Its impact on the floodplain and
floodplain management**.**

**Session 10**: Stream and River Ecology

**Author**: Susan Bolton, Ph.D., P.E.

**Time 75 minutes**

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

# Objectives: (PP1 Title, PP2 and PP3, Objectives)

At the end of this session, the students will be able to:

> 10.1 Explain the importance of river systems and their connectivity to
> oceans.
>
> 10.2 Describe the four dimensions of river ecosystems.
>
> 10.3 Describe major conceptual theories in stream ecology and how
> energy flow and nutrient cycling concepts vary among them.
>
> 10.4 Describe how species are distributed in space and time.
>
> 10.5 Discuss stream and river ecology within the context case study
> floodplains

**Scope:**

This session describes the global importance of freshwater. Students
learn how little freshwater exists in the form of lakes and rivers and
how streams are linked to oceans. The four dimensions of stream flow are
discussed. This leads to a discussion of the major theories used to
conceptualize stream ecology, the ways in which energy flows through
aquatic systems, and how nutrients are cycled through aquatic systems.
Understanding the spatial and temporal distribution of stream processes
leads to a discussion of how riverine species are distributed in space
and time. For homework, students will select a river of interest and
discuss how the various theories may or not be useful in analysis of
their river. They will also collect sources of information on species
distributions in their river.

**Readings:**

*Student and Instructor Reading:*

Junk et al. 1989. "The flood pulse concept in river-floodplain system."
*Canadian Special Publication of Fisheries and Aquatic Sciences*.
106:110-127.

Montgomery, D.R. 1999. "Process domains and the river continuum." *J. of
the Am. Water Resources Assoc*. 36:397-410.

Poole, G. 2002. "Fluvial landscape ecology: addressing uniqueness within
the river discontinuum." *Freshwater Biology* 47:641-660

Stanford, et al. 1988." Serial discontinuity in a large river system.
"*Verhandlungen der Internationalen Vereinigung fur Theoretische und
Angewandte Limnologie*. 23: 114-118.

Stanford and Ward. 1993. "An ecosystem perspective of alluvial rivers:
connectivity and the hyporheic corridor." *J. of the N.A. Benthological
Soc*. 12:48-60

Tockner et al. 2000. "An extension of the flood pulse concept."
*Hydrological Processes*. 14:2861-2883.

Vannote, et al. 1980. "The river continuum concept." *Can. J. Fisheries
and Aquatic Sciences* 37:130-137.

Ward and Stanford. 1995. "The serial discontinuity concept: extending
the model to floodplain rivers." *Regulated Rivers: Research and
Management.* 10:159-168.

Ward, J.V. 1989. "The four-dimensional nature of lotic ecosystems**."**
*J. of the N.A. Benthological Society*. 8:2-8.

Ward, J.V. 2001. "Biodiversity: Towards a unifying theme for river
ecology." *Freshwater Biology* 46:807-819.

*Additional Instructor Reading:*

Hutson, Susan S., Nancy L. Barber, Joan F. Kenny, Kristin S. Linsey,
Deborah S. Lumia, and Molly A. Maupin. 2000. "Estimated Use of Water in
the United States in 2000**."** *USGS Circular 1268**.*** Abstract is in
water_use_USGS.doc file.

**Note:** This Instructor reading is very useful for Objective 9.1

**General Requirements:**

The instructor should select a river of interest to the region or the
students. For the overall assignment, students will gather information
on a river of interest. See homework assignment and end of outline.

**Objective 10.1 Explain the importance of river systems and their
connectivity to oceans. (PP3 Objective)**

**Requirements:**

Instructor should select a river from the latest publication on
endangered rivers by the American River Society (for 2003, see
<http://www.amrivers.org/doc_repository/MostEndangeredRivers2003.pdf>).
The EPA OWOW surf-your-watershed website is also a good resource. The
material will be more interesting if the instructor provides information
from the 2 websites or other sources on issues of water distribution and
use. For example, what is the source of drinking water in your region,
what are the major threats to river ecology such as pollution or
development?

**Note:**

Distribute hard copies of the word file 'water_use_USGS.doc' as a
handout.

**Remarks:**

I. Streamflow provides both human and ecosystem services. (PP4)

A. Humans use water for many different reasons. **(PP5)**

1\. In the U.S. almost 50% is used for thermoelectric nuclear power,
mostly for cooling (includes both freshwater and saline water)

2\. Another 34% is used for irrigation for crops (largest user of
freshwater)

3\. Public and domestic (household wells) use is about 12% of total
usage

4\. Other uses include mining, aquaculture, livestock, and industry

B. Freshwater streamflow to the oceans is a critical part of the marine
ecosystem.

1\. The 3 regions of the US with the highest freshwater inflow to the
oceans have significant fishery resources. **(PP6)**

a\. Mississippi River and the Gulf of Mexico

b\. Columbia River and the Pacific Ocean

c\. Multiple streams to the Gulf of Alaska

2.  Streams and rivers affect the temperature, salinity, organic matter
    level, nutrient and sediment loads and light where they enter the
    ocean. **(PP7)**

    a.  Changes in water quality in the Mississippi have altered
        nitrogen:phosphorus:silica ratios in the Gulf of Mexico and
        altered the phytoplankton community

    b.  Freshwater lens may last months or even a year in the Gulf

    c.  Extent of 'dead zone' of water without oxygen is affected by
        nutrient levels in Mississippi

3.  Worldwide there is evidence of increased number of algal bloom and
    more toxic blooms presumable from alterations in freshwater inputs
    to the ocean **(PP8)**

4.  Role of freshwater inputs varies by river and region

5.  Alterations of streamflow from flood management activities or river
    restoration may ultimately affect marine ecosystems

**Objective 10.2 Describe the four dimensions of river ecosystems (PP9,
Objective)**

**Note:**

**(PP10, 4 Dimensions of a stream)** Slide 10 should be used to
illustrate the four dimensions of streams and trigger discussion.

**Remarks:**

I. Stream processes occur in four dimensions:

-   Longitudinal,

-   Lateral,

-   Vertical, and

-   Temporal

A. The longitudinal dimension looks at streams from their headwaters to
their mouths.

B. Three broadly defined zones can be recognized in the **longitudinal
dimension**: headwaters, transfer zones, and depositional zones. Other
terms sometimes seen for these zones are source, transport, and response
zones.

1\. Headwaters or source: Compared to the other zones, the headwater
zone typically has the lowest stream flow, the steepest slopes, and the
highest erosion rates compared to deposition rates.

2\. Transfer or transport zones: Typically has slightly less steep
slopes, shows an increase in stream flow, and exhibits both erosional
and depositional processes.

3\. Depositional or response zones: Typically has the lowest stream
slope, the most stream flow, and deposition usually exceeds erosion.

C. The **lateral dimension** is from side to side across the river and
its floodplain.

1\. The stream channel typically contains water.

2\. The low floodplains are flooded frequently.

3\. Higher floodplains are rarely flooded.

4\. Terraces are former floodplains that are no longer flooded and the
hill slopes that form the valley walls extend into the uplands that go
to the watershed boundary.

D. The **vertical dimension** includes surface water and ground water
and their interactions, including the hyporheic zone.

1\. Streams and the aquatic environment associated with them are not
entirely surface features.

2\. Depending on the stream, there can be extensive exchange of material
between surface water and ground water extending far beyond and below
the visible stream channel.

E. The **temporal dimension** varies in length from short-term temporary
changes to long-term evolutionary change.

1\. Features and conditions associated with the other three dimensions
should never be thought of as permanent in time or space.

**Objective 10.3** **Describe major conceptual theories in stream
ecology (PP11, Objective)**

**Note:**

Interesting case studies on the importance of flood pulses from the
Southwest, Midwest and Southeast can be found in Middleton, B. A. (ed.)
2002. *Flood Pulsing in Wetlands: Restoring the Natural Hydrologic
Balance.* John Wiley and Sons, New York. The material will be improved
if the instructor selects one of these case studies to discuss
flood-pulse issues. For section 9.3 IV, the Ward and Tockner (2001)
paper is very useful.

Review already displayed **PP 10.12-13** to illustrate the river
continuum concept. **(PP12, River Continuum Concept, and PP13, River
Continuum Diagram)**

**Remarks:**

I. The River Continuum Concept (RCC)

A. The River Continuum Concept was an early attempt to characterize and
classify ecosystem processes in rivers.

1\. RCC describes expected changes in biological characteristics that
reflect the changing physical conditions (e.g. stream width, stream
depth, flow volume, temperature, and sediment size) from headwaters to
river mouths.

B. Changes in the source of energy (authochthonous vs allocthonous), the
production/respiration (P/R) ratio, and CPOM/FPOM ratio affect species
composition and trophic relationships in stream ecosystems.

C. **Headwater streams** tend to be narrow and shaded, which limits
autochthonous production.

1\. Most of the energy for the system comes from terrestrial organic
matter that is delivered to the stream.

2\. Stream temperature is usually relatively cool

3\. Bed sediment sizes are relatively large.

4\. Flows are relatively low.

5\. Organic input tends to be coarse and woody.

D. **Mid-size streams** are wider and typically receive more sunlight
that allows for more in-stream or autochthonous organic matter
production.

1\. More sunlight also tends to increase the stream water temperature.

2\. Organic matter is a mix of coarse local inputs and fine matter
transported from upstream.

3\. Bed sediment size has decreased compared to headwaters.

E. **Large streams** are even wider, but the increase in fine
particulate matter and fine sediment carried by the stream may limit
sunlight penetration and thus in-stream organic matter production.

1\. Streambeds tend to be very fine grained.

2\. Water temperatures are warmer than higher up in the stream system.

F. The greatest explanatory power is in streams with strong,
uninterrupted longitudinal linkages (high levels of stream confinement),
minimal flooding, and few major tributary junctions.

1\. The River Continuum Concept largely ignored lateral and vertical
connectivity influences.

II\. The Flood-Pulse Concept (PP14, River-Pulse)

A. The Flood-Pulse Concept recognized the lateral connectivity of
streams with their floodplains and riparian systems.

B. Flood pulses are episodic inundation of the land that is adjacent to
rivers.

1\. It was originally noted in the dramatic changes in water levels in
the Amazon Basin.

2\. The interconnection of floodplains and rivers is important because
flood pulse is a major driver for production, decomposition, and
consumption.

C. Water fluctuation also drives successional processes of riverine
vegetation.

1\. Many floodplain adapted species require periodic flooding for seed
dispersal, germination, and recruitment (e.g. many species of cottonwood
(*Populus spp.)* and *Boltonia decurrens,* an endangered riparian plant
in Illinois).

2\. Floods create a bare, moist, mineral substrate that is ideal for
many species for germination.

D. Flood pulses also recharge aquifers, moisten surface soils, and
deposit important nutrients on the floodplain.

E. The flood pulse concept recognizes that periodic flooding is part of
the natural dynamic equilibrium of riverine systems.

1\. Floods are not viewed as either 'perturbances' or 'disturbances.'

2\. Unmanaged riverine systems have evolved in concert with the expected
occurrence of floods.

F. The highest explanatory power is in streams where the geomorphology
facilitates lateral connectivity.

1\. For example, streams in wide valleys with low floodplain terraces.

III\. The Hyporheic Corridor Concept (PP15, River Corridor)

A. The Hyporheic Corridor Concept looks at the vertical integration of
streams with the surrounding ground water and hyporheic zone.

> 1\. The hyporheic zone is the area below the streambed where water
> percolates through spaces between the rocks and cobbles.

B. The Hyporheic Corridor Concept describes the important of vertical
exchange of materials between surface water and shallow sub-surface
water.

1\. The existence of the hyporheic zone was originally identified by
observing the presence of stream organisms and unusually high dissolved
oxygen concentrations in shallow ground water beneath and along side
streams.

2\. Water temperature and movement of solute tracers can also be used to
identify hyporheic zones. The greatest exchange of materials and
interaction between surface water and hyporheic water takes place via
relatively short flow paths.

3\. These flow paths are on the order of centimeters to tens of meters
over which water enters or leaves the streams or hyporheic zones.

C. There are several reasons why the shorter, faster exchanges that
occur via the hyporheic zone should be looked at separately from the
longer, slower exchanges that take place between surface water and
deeper ground water.

D. By definitions, exchanges between surface and hyporheic water occur
many times within a single study reach of 10s to 100s of meters.

1\. Groundwater flow paths enter and leave a channel reach only once.

2\. Frequent, rapid interaction of surface water with the hyporheic
water enhances the microbial activity of the hyporheic zone.

3\. This increases the rates of nitrification, uptake of dissolved
organic carbon, and microbial oxidation of manganese.

D. The highest explanatory power is in streams where the geomorphology
facilitates vertical or subsurface lateral connectivity.

1\. For example, streams in wide valleys with highly permeable soils.

IV\. The Serial Discontinuity Concept (PP16, Serial Discontinuity
Concept)

A. The serial discontinuity concept recognized that streams do not
change uniformly in the longitudinal direction.

B. Changes in geomorphology along the stream network and tributary
junctions from systems with different climate and physiography interrupt
expected downstream changes described by the River Continuum Concept.

C. Dams and other regulatory structures also create significant changes
in material processing and transport longitudinally in streams.

1\. Sediments and coarse organic materials tend to be trapped behind
dams and not transported downstream.

D. The concept has been expanded to include vertical and lateral
connectivity. The influence of longitudinal vs. vertical vs. lateral
connectivity varies depending on position along the river network.

1\. Longitudinal connectivity is most important in constrained
headwaters.

2\. Vertical connectivity is most developed in the middle (and often
braided) channels.

3\. Lateral connectivity is most developed and complex in usually
meandering channels of lowland and coastal plains.

E. The highest explanatory power is below dams or other structures that
significantly, and more or less permanently, alter transport of water,
sediment, and nutrients downstream.

V. The Biodiversity Concept (PP17, Biodiversity Concept)

A. The Biodiversity Concept attempts to integrate the many scales
(temporal and spatial) of river process, function, and species community
diversity into one integrative theme.

B. The connectivity of the lateral, longitudinal, and vertical
dimensions of riverine systems changes with different water levels.

1\. The temporal and spatial variation in the conditions within these
various components provides much physical and biological heterogeneity
that is reflected in the relatively high biodiversity found in riverine
systems compared to uplands.

C. The concept of **biodiversity**, one that is broader than the
community- oriented concept of species diversity, presents an
integrative perspective that links ecology with evolution, genetics, and
biogeography.

1\. It also can illustrate how habitat/niche diversity is related to
disturbance regimes and functional processes.

2\. It encourages thinking about riverine ecosystems in a hierarchical
fashion and provides a basis for effective floodplain management and
restoration.

**Objective 10.4 Describe how species are distributed in space and
time**

**Note: PP9.18-19** to illustrate species and habitat distributions in
river ecosystems**. (PP18, Objective; PP19, How Species...; PP21,
Selected)**

**Remarks:**

I. Riverine organisms occupy many different types of habitats:

-   water column,

-   river bottom (benthic),

-   hyporheic zone,

-   stream margins, and

-   floodplains.

A. Fish are perhaps the most well known vertebrates in freshwater
systems.

1\. In North American streams, darters (Percidae), minnows (Cyprinidae),
and suckers (Castomidae) are the most common taxa.

B. Some fish migrate long distances and need access to both freshwater
and salt water to reproduce and survive.

1\. Anadromous fish, like salmon, reproduce (spawn) in freshwater,
migrate to salt water to mature, then return to freshwater to spawn and
die.

2\. Catadromous fish, like eels, spawn in the ocean, the larvae migrate
to freshwater to mature, and then return to the ocean to spawn.

C. Species distribution is affected by factors such as

-   substrate,

-   temperature,

-   dissolved oxygen concentrations,

-   habitat availability,

-   current speed, and

-   feeding requirements, as well as,

-   evolution and population isolation since the Tertiary Era and
    modern-day species introductions.

D. **Macroinvertebrates** (large aquatic insects, worms, leeches and
water mites) are common in many streams.

1\. Their larvae are important material processors and are often grouped
by feeding behavior:

-   grazers,

-   shredders,

-   filterers, and

-   predators.

2\. The river continuum theory describes how the relative abundance of
each feeding group changes from upstream to downstream

3\. (PP13) Macroinvertebrates live on the substrate (bed) of the river
and are important food for other species, such as fish.

4\. They also play a role in shredding CPOM, which facilitates its
breakdown into base nutrients.

5\. They have also been used as indicators of stream condition in what
is called the Benthic Index of Biological Indicators (B-IBI)

6\. Many species drift (detach from the substrate and get transported
downstream) on a diurnal cycle. This can serve as a form of colonization
of areas that may have been depleted due to floods or drought.

E. The **hyporheic zone** contains a variety of species, mostly
invertebrates. Some species appear to be unique to the hyporheic zone
while others are also found either in surface water or ground water.

1\. The hyporheic environment is more stable than the substrate of a
flowing river. It consists of the spaces between inorganic particles in
the hyporheic zone and is seldom disturbed except by very large, rare
flood events.

2\. They hyporheic zone also has a diverse microbial population which
facilitates nutrient transformations.

F. Aquatic plants consist of **algae**, **lichens**, and
**macrophytes**. They are often grouped by the methods in which they
attach themselves to the ground.

1\. Algae are the most significant contributors to primary production in
most streams.

2\. In addition to contributing to autochthonous production, macrophytes
also provide surfaces for the attachment of algae and microbes and other
fauna such as snails, as well as providing calm areas for fish to rest.

G. Other fauna found in or along rivers include mammals, birds,
crustacea, reptiles, and amphibia.

1\. Species richness varies along a transect, from the valley wall to
the center of the river. Review illustrations included in PP.21. (PP21,
How Species are distributed...)

Homework:

Notes: Either the instructor or the class as a whole or each individual
should select a river of interest for this assignment. For best results
river should be one for which there is ample information. Two good
places to start are the American Rivers web site
<http://www.amrivers.org/doc_repository/MostEndangeredRivers2003.pdf>)
and the US Environmental Agency Office of Water, Oceans and Wetlands web
page and specifically the 'surf your watershed' page.

Students will gather information on a river of interest. Students should
determine water use in the river basin and the source of the water
resource. Student will also be asked to identify which species live (or
used) to live in various habitats from the river to the edge of the
floodplain. They should evaluate which of the major concepts has the
most explanatory power for their river. Students should prepare brief
talking points about a taxa of interest and its status, the relevance of
various theoretical concepts for their river and water use and
distribution in their river. A class discussion of this homework will
take place at the beginning of the next class meeting.

**Objective 10.5 Discuss stream and river ecology within the context
case study floodplains.**

**Remarks:**

A.  Teams should be given time to discuss how stream and river
    ecological principles impact their case study floodplains**.**

**References**

Angelier, E. 2003. *Ecology of Streams and Rivers.* Science Publishers,
Enfield, NH.

Gerritsen, J., and M.T. Barbour. 2000. "Apples, oranges and ecoregions:
on determining pattern in aquatic assemblages." *J. of the North
American Benthological Society* 19(3):487-496.

Giller, P.S. and B. Mamqvist. 1998. *The Biology of Streams and Rivers*.
Oxford University Press, Oxford.

Heinrich, S., N. Bond, R. Garvine, G. Kineke, and S. Lohrenz. 2000.
*Coastal Ocean Processes CoOp: Transport and Transformation Processes
over Continental Shelves with Substantial Freshwater Inflow.* University
of Maryland Center for Environmental Science Technical Report TS 237-00.

Hutson, Susan S., Nancy L. Barber, Joan F. Kenny, Kristin S. Linsey,
Deborah S. Lumia, and Molly A. Maupin. 2000. "Estimated Use of Water in
the United States in 2000**."** *USGS Circular 1268**.*** Abstract is in
water_use_USGS.doc file.

Jones, J.B., and P.J. Mulholland (eds.). 2000. *Streams and Ground
Waters.* Academic Press, Sand Diego, CA.

Junk et al. 1989. "The flood pulse concept in river-floodplain system."
*Can. Spec. Pub. of Fisheries and Aquatic Sciences.* 106:110-127.

Middleton, B. (ed.). 2002. *Flood Pulsing in Wetlands: Restoring the
Natural Hydrological Balance.* John Wiley & Sons, Inc., New York.

Montgomery, D.R. 1999. "Process domains and the river continuum." *J. of
the Am. Water Resources Assoc.* 36:397-410.

Poole, G. 2002. "Fluvial landscape ecology: addressing uniqueness within
the river discontinuum." *Freshwater Biology* 47:641-660

Rabalais, N. N**.**, R. E. Turner, D. Justic, Q. Dortch, W. J. Wiseman,
Jr. and B. K. Sen Gupta. 1996. Nutrient changes in the Mississippi River
and system responses on the adjacent continental shelf. *Estuaries*
19(2B): 386-407.

Robinson, C.T., K Tockner, and J.V. Ward. 2002. "The fauna of dynamic
riverine landscapes." *Freshwater Biology* 47:661-677.

Stanford, et al. 1988. "Serial discontinuity in a large river system."
*Verhandlungen der Internationalen Vereinigung fur Theoretische und
Angewandte Limnologie*. 23: 114-118.

Stanford and Ward. 1993. "An ecosystem perspective of alluvial rivers:
connectivity and the hyporheic corridor." *J. of the North American
Benthological Society*. 12:48-60

Stanford and Ward. 2001. "Revisting the serial discontinuity concept."
*Regulated Rivers: Research and Managemen*t 17:303-310.

Tockner et al. 2000. "An extension of the flood pulse concept."
*Hydrological Processes.* 14:2861-2883.

Turner, R.E. and N. N. Rabalais. 1991. Changes in Mississippi River
water quality this century and implications for coastal food webs.
*BioScience* 41(3): 140-147.

Vannote, et al. 1980. "The river continuum concept." *Can. J. Fisheries
and Aq. Sciences* 37:130-137.

Ward, J.V. 1989. "The four-dimensional nature of lotic ecosystems**."**
*J. of the N.A. Benthological Society*. 8:2-8.

Ward, J.V. 2001. "Biodiversity: Towards a unifying theme for river
ecology." *Freshwater Biology* 46:807-819.

Ward and Stanford. 1995. "The serial discontinuity concept: extending
the model to floodplain rivers." *Regulated Rivers: Research and
Management*. 10:159-168.

Ward, J.V., K. Tockner, and D.B. Arscott, and C. Claret. 2002. "Riverine
landscape diversity." *Freshwater Biology* 47:517-539.

Ward, J.V., K. Tockner, and F. Schiemer. 1999. "Biodiversity of
floodplain river ecosystems: Ecotones and connectivity." *Regulated
Rivers: Research and Management* 15:125-139.

Wissmar, R.C., and P.A. Bisson (eds.). *Strategies for Restoring River
Ecosystems: Sources of Variability and Uncertainty in Natural and
Managed Systems.* 2003. American Fisheries Society, Bethesda, MD.