Canadian Water Quality Guidelines
for the Protection of Aquatic Life
PHOSPHORUS: CANADIAN GUIDANCE FRAMEWORK
FOR THE MANAGEMENT OF FRESHWATER SYSTEMS
5
the baseline is not observed, then there is considered a
low risk of adverse effects, and only monitoring is
required for these sites. If the increase from the baseline
is greater than 50%, the risk of observable effects is
considered to be high, and further assessment is
recommended.
Recommended Assessment Tools
The recommended assessment options currently in use in
Canada, the US, and other parts of the world are
presented in detail in Environment Canada (2004). In
summary, the tools fall into the following three
categories:
i. A water quality index can be used as a surrogate for
phosphorus as it can provide a single value that
identifies the current state of the ecosystem,
including the percent change from the
reference/baseline condition (e.g., Johnes et al.
1994).
ii. Multivariate methods can also assist in comparing
current conditions to baseline conditions, and the
degree of impairment can be identified both spatially
and temporally (Reynoldson and Day 1998; Kilgour
et al. 1998; OMOE 1999).
iii. Predictive models can be applied for the management
of phosphorus. For example, Lakeshore Capacity
(Dillon and Rigler 1975) and paleoecology based
phosphorus reconstruction (Dixit et al. 1999) models
have been successfully used to estimate baseline
phosphorus concentrations and to assess the
magnitude and the rate of change.
These assessment tools should be viewed with the caveat
that many of them were developed for specific water
types or for specific areas with underlying topographic
and geological assumptions. Although many of these
methods can be adapted to the specific user’s
situation/need, care must be taken in selecting an
approach that is both technically feasible and realistic to
the user’s needs. Furthermore, the application of any
assessment tool in defining phosphorus concentration
may not be exclusive, and it may be necessary to adapt a
combination of approaches.
Management Decisions
Once the potential increases in phosphorus concentrations
have been assessed, the results are compared to the
original goals (i.e., reference or baseline conditions) set at
the beginning of the framework. The degree of change is
then assessed on a management level, and the question
raised, “are these changes acceptable?”.
Management decisions are a critical step in the
framework that links back to the objectives and outcomes
of the program via monitoring. Management of
phosphorus should include both short-term management
strategies and options, which primarily focus on
operational activities; and long-term management
strategies, which focus on nutrient reduction, flow
management, education, monitoring, and research.
References
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