Monitoring Program Objectives
patterns should be evaluated to determine if individual bays, or subbasins of
significantly different mean depth, are hydrodynamically distinct. Based on the
location pollutant influx and areas of use or critical habitat conditions, the
minimum number of stations, with one at the deepest part of the
interest, should be chosen.
Basin mixing and variable type should be evaluated prior to determining sampling
depth. For unstratified lakes (lakes with a uniform temperature from surface to
sediments), a surface (one may be enough), mid-depth, and near-bottom samples
may be appropriate. An alternative protocol is to take an integrated sample from
just above the bottom to the surface. For stratified lakes, one surface sample, one
in the metalimnion, one at the mid-depth of the hypolimnion, and one near the
bottom of the sediments may be required (Wedepohl et al. 1990).
Level I can be used for evaluating current conditions, problem documentation,
frequent violations in standards, trend detection in some cases, or measuring large
impacts. Many state agency monitoring programs address level I objectives.
Trend detection for level I can be performed when background variability is low
and the level of treatment, pollutant control, and restoration accomplishments are
high. The watershed should be relatively small (e.g., less than approximately
30,000 acres) and all or nearly all of the critical area pollutant sources must be
treated for a sustained period. Level II monitoring, which is more detailed to
quantify and explain greater variability, should be used otherwise. If the objective
is to determine an impact or a cause-and-effect relationship, then level II
monitoring is needed.
Level I trend detection employs the use of relatively inexpensive methods, such
as measuring Secchi depth, grab samplin, for chemical concentrations, and
measuring simple habitat variables. On the other hand, these measurements reflect
a complex of factors that may be difficult to interpret. It is helpful to measure
appropriate explanatory variables to account other sources of variability.
The following subsections describe variables common to level I monitoring of or
biology, habitat, and chemical/physical characteristics of a water resource.
Biological monitoring provides the most direct measure of use attainment related
toaquaticlife. Organisms respond toanaggregateofstressfactors, includingthose
not monitored by chemical or habitat protocols. Chemical monitoring and
bioassay alone may fail to directly assess pollutant-induced degradation or partial
restoration of biota. In addition, the public may understand the
of biological monitoring more easily than other methods (Zaroban 1988).
However, biological monitoring may be relatively field-intensive and it requires
a trained staff, with knowledge of local biota and their habitat, in order to obtain
high information content and to maintain quality control. Sampling bias can make
protocols subject to errors. The effects of fish stocking or other management
activities may confound analysis of treatment effect and natural regeneration.
Many techniques are available for biological data analysis but some require
modification to considerregional and seasonal variability, including life cycle and
behavioral aspects (Zaroban 1988).