Monitoring Program Objectives
value if the response in the receiving water is expected to be slow and improve-
ments are not likely to occur for many years. For instance, measuring the
effectiveness of animal waste control on one tributary of a large lake with several
important tributaries (such as Lake Champlain) may require monitoring phospho-
rus loads, since in-lake monitoring is unlikely to measure the change in the mean
state measures of the lake.
phosphorus concentration or
A pollutant budget may be a useful decision tool to determine variables and
frequency of monitoring and expected information from load monitoring. The
budget accounts for a mass-balance of a pollutant and water input by source,
including ground water and atmospheric deposition, all output, and changes in
storage. The budget may show the magnitude and relative importance of con-
trolled and uncontrolled sources (atmospheric deposition, resuspension from
sediments, streambank erosion point sources, septic tanks).
Minimum Detectable
The most defensible measure of land treatment project performance is a
Change and Making
designed and well-implemented monitoring program that examines statistically
the relationship between the project's pollution control activities and a change in
Program Decisions
water quality. Planning an adequate monitoring program considers extent of
treatment, relative magnitude of sources, system variability, and the minimum
detectablechange(MDC) (Spooneret al. 1987a) needed in a
quality variable
to document a statistically significant change.
An analysis of historical data to determine the MDC may serve to estimate the
amount of time needed (number of years or seasons) to show a significant trend.
For a monitoring program underway, the variability and trends observed may be
calculated at regular intervals to determine if the sampling program can realisti-
cally meet thequantitative objectives for trend detection and when to proceed with
sampling or when to stop.
Variable Selection
Monitoring for each objective requires a different approach. Monitoring to
evaluate current conditions should focus on critical variables related to designated
water body use and those variables expected to respond to management activities.
For violations of standards, the choice of variable is specified by the standard. To
assess ecological integrity, monitor a set of variables that show how an ecosystem
compares to a control or one that has a composition, structure, and function
essentially unimpaired by human activities (Karret al. 1986). For trend detection,
the response variable and explanatory variable must be carefully selected to show
treatment effect and account for changes in system variability.
Variability and
Sources of variability include climate, weather, watershed characteristics, and
Explanatory Variables
human activities. Variability may be in daily, seasonal, year-to-year patterns, or
have some random component. Measuring and accounting for sources in variabil-
ity increases monitoring sensitivity and reduces the MDC.
Explanatory variables such as those in Table 3.2 can account for the influence of
climate, hydrology, land use, and other factors. Land treatment variables are also
important as explanatory variables. The appropriate explanatory variable or set of
variables is directly related to the primary variable/pollutant of concern. Incorpo-
ration of explanatory variables into the study increases the analyst's ability to
isolate true water quality trends due to land treatment. For example, antecedent
precipitation, stream discharge, or water table depth may be used to quantify the
3.3
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