Subject: Watershed Management #4
From: [email-masked] (Paul Cass)
Date: Mon, 28 Feb 1994 17:13:01 GMT
Newsgroups: sci.bio.ecology

The following article is part of a watershed seminar held at Oregon
State University in Spring, 1993.  The summary was written by Penny Cass and
approved by the speaker.  This article is part of a publication that can
be ordered from the Oregon Water Resources Research Institute, OSU,
Strand Ag Hall 210, Corvallis, OR 97331-2208 (503) 737-4023.  The
article may be reprinted without permission for educational purposes.  If
used, Please send 2 copies of your publication to OWRRI.

ASSESSMENT OF WATERSHED HEALTH
Robert Hughes, Aquatic Ecologist, Mantech, Corvallis, Oregon

Europeans use the term "catchment" to describe drainage basins; to
them a "watershed" is the drainage divide.  Hughes prefers the word
"catchment" because it is more universal and captures the image of
holding, storing, or "catching" water, rather than merely "shedding" it.
Water bodies reflect their catchments; relatively clean water seeps
through the catchment and emerges carrying the signature of the
landscape it has passed through.  The health of much of the landscape is
deteriorating and water bodies are reflecting this change.  Stemming the
degradation involves monitoring and assessing regional patterns and
establishing a network of aquatic preserves.

Catchment Development and Character
All around us we see evidence of past landscape sculpturing by water
(Leopold et al., 1964).  Tectonic forces yield the raw material that water
uses to create the hills and hummocks and landscape patterns. 
Worldwide, water has shaped much of the earth's topography.

Precipitation leaching through and eroding the soils and rocks
determines the quality and character of the land and it also determines
the quality and character of the water.  Differences in the character of
the water and land influence the organisms that survive in a particular
region.

Six major landscape features determine the character of water bodies. 
Climate, topography, surficial geology, soil, vegetation, and land use are
the landscape determinants of water body health.  These six
characteristics influence a water body's flow regime, habitat structure,
food sources, migration barriers, and water quality.
Just as landscape character determines water quality, the water can be
used to determine the health of the surrounding land.  Catchment health
is reflected in water turbidity, color, alkalinity, and hardness, and in the
chloride, nitrogen, and phosphorus content.  Water chemistry illustrates
catchment health the way a blood sample portrays the health of a
human patient.

Urban, pasture, and forest land uses all affect regional water chemistry,
but studies have shown that cities have the largest affect on water
quality at a site.  The condition of a riparian area, the floodplain along a
river channel, also influences water quality.  Riparian areas support
vegetation and food sources, regulate water temperature and channel
morphology, provide places of concealment for fish and water organisms,
and provide a land use buffer that traps pollutants and sediments.  Over
70 percent of a catchment's wildlife depend on riparian areas for
habitat.

Demonstrating Regional Patterns
Water bodies demonstrate regional patterns on large scales, like biomes,
and on smaller scales.  Ecoregions have been mapped for the United
States based on the differing character of regional landscapes and water
bodies (Figure 1).

Oregon can be divided hierarchically into 8 to 40 ecoregions, each with
different topography, vegetation, climate, and water.  Research has
shown that distinct ecoregions have different fish assemblages.  Diverse
fish groups are supported by the special character of an ecoregion and
are affected by the variety of land uses within the region.  Separate
water basins are related to neighboring basins by common ecoregion
characteristics.  Ecoregion analysis looks at the community of
catchments rather than the individual populations of a single catchment. 
Figure 2 shows how fish assemblages can reflect an Ecoregion within a
basin rather than being similar throughout the entire catchment.

Understanding the distinct character of each ecoregion is useful in
assessing and managing ecosystem health.  Using ecoregions, researchers
can determine the natural conditions, such as cold or warm water,
without measuring each stream, and assess what deviations are occurring
by locating water bodies that have changed from predominant regional
patterns.  Regional patterns suggest that most of Oregon's streams were
once appropriate habitats for salmonids at some times of the year.

Assessing Deteriorating Health
What is a healthy watershed?  For many ecologists, health is often
synonymous with biological integrity, which means "the ability to support
and maintain a balanced, integrated, adaptive community of organisms
having a composition, diversity, and functional organization comparable
to that of the natural habitats of the region" (Frey, 1975; Karr &
Dudley, 1981).  Figure 3 illustrates the variety of components involved in
biological diversity.

Examples of deteriorating health exist on all scales of diversity ~
genetic, species, assemblages, fauna, ecosystem, or landscape (Hughes
and Noss, 1992).  Genetically, at least 23 percent of anadromous Pacific
salmonids are at risk; nearly half of the troubled stocks are in Oregon. 
On a species level, 63 percent of California fishes are extinct or at risk. 
Assemblages of fish in the Great Lakes are deteriorating as evidenced
by the 82 percent drop in the commercial catch of native salmonids. At
the fauna level, 20 percent of the world's fishes are extinct or at risk. 
To illustrate the decline in ecosystem integrity, only 2 percent of U.S.
streams are worthy of a wild and scenic status.

Establishing Aquatic Preserves
A network of aquatic preserves would help protect ecosystem variety,
save endangered species, and provide scientific reference sites.  Because
terrestrial preserves fail to adequately protect aquatic organisms,
establishing these new preserves would facilitate better ecosystem
management.  Protected from multiple stresses, these research
catchments would provide information on the biological criteria that the
state is required to produce in order to meet new water quality
regulations.

Protecting a number of different species and a number of different
stocks requires creating preserves in each ecoregion and in each basin. 
A committee of thirteen biologists in Oregon developed a proposed
network of preserves, which was reviewed by 80 aquatic biologists. 
Much of the critical habitat is on public land and there is some overlap
with existing or proposed reserves for terrestrial species.  However,
current reserves and resource management ptactices underprotect
aquatic species.

Creating a Monitoring Program
Discovering problems after species are already at risk illustrates an
inadequate monitoring program.  For 40 years, Oregon measured
returning salmon at particular index sites.  Because the sites were
located on the best streams in the Coast Range, extrapolated statewide
fish totals overestimated fish counts.  These inflated numbers were
subsequently used to set harvest limits.  Fish catches may have been
established at about five times the level that more accurate assessments
would have allowed.  

These monitoring problems can be addressed by using more rigorous
statistical processes when establishing sample sites.  Pilot programs in
Oregon use randomly generated sites in a variety of basins monitored on
a rotating basis. 

Sedimentary diatoms, the algal "skeletons" in the bottoms of lakes, can
illustrate the historical changes within a water body.  Diatom
disturbance indexes tend to correlate with the human impacts within a
catchment.  Plotting the character of disturbance can paint an ecosystem
picture of regional landscape health.  Use of multiple metrics on
multiple fish assemblages increases the power of management agencies
to assess the status and trends of aquatic ecosystems and their
catchments.

Protecting water quality and terrestrial and aquatic populations require
an understanding of the different landscape features that can affect a
catchment.  Focusing on single species preservation ignores the essential
connection between species and their habitat, while ecosystem
management focuses on habitat in efforts to protect multiple species. 
By characterizing the physical and chemical processes within ecoregions,
managers can compare the current health of a catchment with the
natural condition of the region.  Establishing aquatic preserves and
creating monitoring programs allows managers to protect existing
healthy population, to aid in the restoration of declining populations,
and to verify assumptions made in management plans.

References:

Hughes, R.M. and R.F. Noss. 1992. Biological Diversity and Biological
Integrity:  Current Concerns for Lakes and Streams.  Fisheries 17:11-19.

Leopold, L.B., M.G. Wolman and J.P. Miller. 1964. Fluvial Processes in
Geomorphology. W.H. Freeman Co. San Francisco.

Noss, R.F. 1990. Indicators for Monitoring Biodiversity: A hierarchical
Approach.  Conservation Biology 4:355-364.

Omernik, J.M. 1987. Ecoregions of the Conterminous United States. 
Annals of the Association of American Geographers 77:118-125.

Omernik, J.M. and G.E. Griffith. 1991. Ecological Regions Versus
Hydrologic Unites: Frameworks for Managing Water Quality. Journal of
Soil and Water Conservation 48:334-340.