Defining A Healthy Watershed

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Defining A Healthy Watershed
Dr. Karl Wood, Director Water Resources Research
Institute Dr. Terrell Baker, Riparian
Ecologist New Mexico State University Las Cruces,
NM
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Websters Definition of Health
1. Physical and mental well-being 2.
Soundness 3. Freedom from defect, pain, or
disease 4. Normality of mental and physical
functions
How does this definition apply to watersheds?
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What are some other terms or phrases used to
describe watersheds?
Brittle and Non-Brittle
Functioning and Non-Functioning
Proper Functioning Condition
Impaired
At Risk
Stable
Sustainable
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Some Related Definitions
Rangeland Health (Natural Research Council
1994) The degree to which the integrity of the
soil and ecological processes of rangeland
ecosystems are maintained
Forest Health (U.S. Forest Service) A condition
wherein a forest has the capacity across the
landscape for renewal, for recovery from a wide
range of disturbances, and for retention of
ecological resiliency, while meeting current and
future needs of people for desired levels of
values, uses, products, and services
Watershed Health (Jones et al. 2002) A state in
which resource management activities sustain
human needs and uses of the watershed while
ensuring that ecological function is maintained
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Why this vision of everything being black or
white, and why are these definitions bothersome?
1. They convey that everything is either
right or wrong. 2. They infer that nature
gives values to society. 3. They also infer
that societys values are mutual across all
lands, both public and private
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Most people have an intuitive idea of what
constitutes a healthy watershed at least, they
believe they can recognize an unhealthy one
when they see it.
Using health to describe watersheds is
probably inappropriate.
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Watershed Conditions Fall Along A Continuum!
How can we express that continuum?
Ecosystem Succession or the Sere is a good
start!
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Concept of the Sere
Example developed in North America by H.C. Cowles
and F.E. Clements about 100 years ago
Climax
Conifers
Deciduous trees
Shrubs
Perennial grasses and forbs
Climate
Annuals
Mosses
Lichens
Bare Rock
Soil depth and richness
Time
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Conifer invasion of a meadow
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Early ponderosa pine savanna
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Ponderosa pine thicket today
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Insects and disease spread in a crowded forest
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Concept of the Sere
Climax
Shrubs
Perennial grasses and forbs
Climate
Annuals
Mosses
Lichens
Bare Rock
Soil depth and richness
Time
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Concept of the Sere
Perennial grasses and forbs
Climax
Climate
Annuals
Mosses
Lichens
Bare Rock
Soil depth and richness
Time
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Concept of the Sere
Climate
Lichens
Climax
Bare Rock
Soil depth and richness
Time
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Would A Society Ever Want To Maintain Bare
Rock Or a Very Low Seral Stage In Its Watereshed?
Example San Angelo, Texas
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General Comments On Ecosystem Succession

• Movement towards climax is called succession

• Movement away from climax is called
  retrogression (e.g. Desertification)

• The kinds of animals different in each seral
  stage.

• The climax seral stage usually does not
  represent the greatest species diversity of
  plants and animals.

• Subclimax seral stages may be maintained by
  continuous or discontinuous perturbations such
  as fire, grazing, hurricanes, etc.

• Multiple equilibrium communities and complex
  successional pathways may be possible within a
  sere.

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Explanations of ecosystem succession have been
modified and expanded by
Gleason 1926 recognized individual species
differences Tansley 1935 proposed more than one
climax for a site Watt 1947 - identified the
importance of patches and disturbance
cycles Egler 1954 noted that species did not
always invade but were present and increased
Pickett 1976 recognized importance of natural
selection and disturbance Connell and Slatyer
1977 proposed facilitation, tolerance, and
inhibition Grime 1979 proposed ruderal,
competitive, and stress-tolerant stages Huston
and Smith 1987 demonstrate 5 successional
patterns sequential succession, divergence,
total suppression, convergence, and
pseudo- cyclic replacement Shugart 1984 claimed
mechanistic rather than deterministic
processes Westoby 1989 explained
state-and-transition models or thresholds Oliver
and Larson 1990 allowed for chaotic or
non-equilibrium cycles
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To manage the watershed, managers need to know
1. What is the potential or climax seral stage
of the watershed?
2. What is the present seral stage of the
watershed?

• Is it all the same or are there different
  seral stages in different parts of the watershed?

3. Are there several acceptable seral stages
and a preferred seral stage of the watershed
and/or its parts?
4. Can the preferred seral stage be achieved
with the present technology, time, legal,
political, and economic constraints?
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Concept of the Sere
Conifers
Most choices are here!
Deciduous trees
Shrubs
Perennial grasses and forbs
Climate
Annuals
Mosses
Lichens
Bare Rock
Soil depth and richness
Time
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If the prime objective is wood products, we may
continue to overgraze, letting in the woodland
and sacrificing watershed values.
If on the other hand the prime objective is
watersheds, we should restore grass, which all
the evidence indicates is a better watershed
cover than either brush or woodland. Aldo
Leopold
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Steps for Watershed Management
Preliminary Assessment and Surveillance
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Preliminary Assessments and Surveillance
Nothing in nature is isolated. Nothing
is without reference to something else. Nothing
achieves meaning apart from that which neighbors
it. Johann Wolfgang von Goethe
There is something fascinating about studies of
science. One gets such wholesale returns of
conjecture out of such trifling investment of
fact. Mark Twain
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Steps for Watershed Management
Preliminary Assessment and Surveillance
Goal Setting
Prioritization and Targeting
Watershed Planning develop document with
roles and implementation strategy
Implementation
Performance evaluation
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For any given response variable such as
Erosion, Runoff, Evaporation, Stream
Temperature, Sediment Load, Arsenic Content,
Plant Growth, Insect Populations, etc.
Questions should be asked
1. What are the natural levels with variations
between hours, days, months, and years?
2. What are maximum potential levels?
3. What are the tolerable levels to sustain the
preferred seral stage?
4. What are the desirable levels?

• Are the desirable levels achievable with present
  technology, time, legal, political, and economic
  constraints?

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Conclusions
Nature abhors a void
Nature abhors topographical prominence
Nature abhors a crowd
Natural changes are often dynamic and
catastrophic with unpleasant consequences for
humans
Human changes of nature may be dynamic and
catastrophic, or static, controlled, predictable,
and beneficial to humans, wildlife, and watersheds
Human influence is most probable for avoiding
catastrophes and assuring ecological, social, and
economic stability.
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Conclusions
A Healthy Watershed preferred seral state is
attained
Sustainability preferred seral stage is
maintained against the processes of succession
and retrogression, including invasions,
especially by exotics
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God bless America!
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Thank you!