assumptions (especially for predictive exercises) and the various means (transformations, etc.) that may
be employed later in the analyses.
18.104.22.168 The Practical Reality
In practice, studies and datasets rarely meet all of the demands set by statistical design. This
does not mean that the data is without value but that its value depends more on sound analysis. Even
where a study has been meticulously designed to meet all needed criteria, circumstances (an extreme
storm event, for example) can quickly cause previous assumptions not to be met. (It is surprising how
common 100- and 500-year events seem to be). For the purpose of data analysis, a safe assumption is
that no particular design has been met.
Assessment methods are also well documented. There are two sources for these and they
include theoretical references such as Thomann and Mueller (1987), Stauffer (1981), Reckhow (1979),
or numerous EPA references such as The Lake and Reservoir Restoration Guidance Manual (Olem
and Flock, eds. 1990). The other source of documentation of assessment methods include the actual
lake assessments. These are instructive for their diversity of problems and methods, the creative
solutions discovered, and their diversity of detail and success.
The simplest lake assessment situation is a small lake which is not morphometrically complex
and which has a central deeper region. For the purposes of assessment of loading, there would only be
one well-defined inflow and one well-defined outflow. There are a large number of lakes that
approximately fit this description, few of which ever need intensive assessment efforts.
The more complex cases seem to demand the greatest assessment resources. These would be
larger, deeper reservoirs with complex morphometries, numerous inflows from varying sources, greatly
variable in-lake conditions depending on spatial location, and outflows complicated by seasonally
changing inflows, power demands, and fisheries habitat needs. If periodic reversal of outflows was
added to this list, several pumped-storage reservoirs would fit the description.
Common and recent lake issues have included; eutrophication, acid rain, fisheries habitat,
release quality, municipal water supply (quality and quantity), industrial use, non-point sources of
pollutants, and others. If these were applied to the most complex lake examples, the methods of
assessment would be very numerous. However, some would be common to all issues because they are
either easy to do or they are fundamental to nearly all issues. The limnological basics which lend
understanding to physical energy exchanges, water movements, and simple chemical processes related
to temperature, dissolved oxygen, and the carbon system relate to most of those fundamental methods.
The practical reality is that we tend to sample as much as is feasible, usually limited by
resources. Such sampling is often performed in a non-random manner, often biased by location and
timing (we rarely sample lakes at night or during storms). Under these circumstances making the best