This section includes a restricted range of assessments of lakes. Risk assessment, for example,
is not addressed. Instead, this section addresses more general questions of assessment of problems,
assessment of results, and assessment of solutions.
In practice, there are simple but important statements of the problems for lake assessment.
What tools should be used? What methods should be used? The tools can be hardware or computer
programs and our choices are well-known and familiar. The methods, however, are varied and greatly
dependent on the particular application. Methods employ the tools to interpret or investigate ideas or
observations and methods are therefore also dependent on the underlying theory, if any, for the
Where the problems are simple, ?do nutrient concentrations exceed regulatory standards?" the
process may also be simple. But even for simple questions, the answer in complex aquatic systems
may involve attention to many details and many technical decisions.
The sources of complexity in lake assessment usually come from two categories of variation of
lake characteristics. Temporal variation is the first and this requires repetitive observation for
assessment. Spatial variation is the other category and this requires multiple observations in space.
They are not incompatible and can combine to require elaborate, expensive assessment efforts.
Temporal complexity is obvious. There are common, universally-recognized periodic
processes in aquatic systems. Primary among these is the diel (24 hour) period associated with the
earth's rotation. This is superimposed on the annual or seasonal cycle. Biota can have even more
novel cycles with larval forms growing continuously for months followed by sudden, brief, synchronous
emergences in adult form for mating and egg laying. Obviously the way we choose to observe such
different events must be different and designed to optimize the clarity of our observations while
minimizing our effort. This is true for all environments, not just for lakes and reservoirs.
Spatial complexity occurs in three dimensions, all of which are commonly sampled in reservoirs.
Reservoirs often have very complex shapes. As a result of this factor, there may be wide ranges of
conditions in a reservoir and our ability to describe or assess them depends on our skill of observation.
Do we emphasize tributary embayments or deeper waters where chemical processes may be more
complex? How do we fairly represent all of the various locations? Again, the way we choose to
observe must optimize the clarity of our observations while minimizing the depletion of our resources.
The answer to these inevitable questions which determine our assessment success are both
theoretical and practical. In this chapter are presented both views with emphasis on the practical view.


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