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The Municipality of King's investigation into lake carrying capacity in 1993
ultimately lead to the implementation of a mathematical model for predicting fluctuations
in trophic state within the Gaspereau watershed. In combination with monitoring
efforts, this model offers a means by which development can proceed without significantly
impacting Kings County water quality.
What is a Model?
A model is simply a mathematical representation of a process or a system. In the
case of the Kings Countymodel, trophic status is represented as a function of lake
morphology, water flow dynamicsor hydrology, local climate, and the characteristics
of shoreline development. This means that the lake and its surroundings are represented
by a series of equations that can predict desired outputs (amount of phosphorous,
chlorophyll a) when certain inputs are known (amount of water, number of lake users).
Models are: 1) an approximation of reality 2) a reflection of our understanding of watershed systems.
They are designed to be a planning tool and the answers they provide are dependent
on how we apply them. The quality of their output is no better than the quality
of our understanding of the system.
Modeling Versus Monitoring
Both modeling and monitoring are useful in attempting to ascertain a lake's
response to phosphorous loading from development . Monitoring is more accurate in
terms of determining present conditions but is also more expensive and time consuming.
It is this reality that makes volunteer monitoring programs, such as that in Kings
County so important, as they provide a cost-effective alternative by which residents
can help protect the water quality of their lakes.
One shortcoming of intermittent monitoring however, relates to the fact that lakes
exhibit high variability in terms of algal response and nutrient concentrations
on both an annual and seasonal basis. Thus, the results may not be representative
of a long term average or mean. Monitoring limits the interpretation of data to
current conditions with no prediction for the future.
This is where the strength of modeling comes into play. The predictive abilities
of models is what persuaded Council to adopt one based on lake carrying capacities,
as well as implement a volunteer lake monitoring program for model verification.
In this manner, planning advisory committees can make informed decisions regarding
future development while maintaining water quality as a high priority.
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