Chapter 2: Program Analysis
2.2.6 Wafer Quality Monitoring,
Lesson: Changes in land use, difficulties in
tracking BMP
and many
Evaluation, and
other factors may hinder documentation of
(continued)
the impact of BMP implementation on
water quality within a particular project
or watershed area.
Lesson:
variables (discharge,
seasons, upstream pollutant concentra-
The Michigan project has been unable
tions, precipitation) should be monitored
to document any real BMP
due to con-
to ensure accurate interpretation of moni-
founding factors such as
level of
toring results. Adjustment for hydrologic
the ef-
implementation, difficulty in
fects of the sub- basin areas that do not have
and meteorologic variables is important
large variations in sources and transport
when quantifying impacts of land
of sediment and nutrients over time, and accu-
or land use on regional water quality.
racy of estimates of BMP
area.
This procedure renders water quality val-
ues that are closer to those that would have
Example: In the Virginia
beneficial ef-
fects
implementation may not be
been measured had there been no change
apparent because the project began after
in climatic variables over time.
addition,
major point sources and some
sources
hydrologic and meteorologic explanatory
were removed. An improving trend was already
variables can be used to account for water
in effect in the estuaries. Manipulation of the
quality variability.
water supply lakes for water withdrawal and
storage of pumped ground water may have
confounded results.
Adjustments for precipitation in water
trend analysis were made by the Florida,
Idaho, and Pennsylvania projects.
Draining of Prairie Rose Lake (Iowa
project) and
of the fish popu-
lation may have obscured some water quality
Stream discharge measurements were
results. Water clarity was highest in 1982-83,
taken concurrently with water quality sampling
following draining of the lake and restocking of
and accounted for in the data analysis in the
Florida Idaho, Maryland, Michigan, Oregon,
the fishery. Since then water clarity has dete-
Pennsylvania, Utah, and Vermont projects
riorated to pre-RCWP levels. Reduction in sedi-
ment delivery due to adoption of
Example: In Oregon, fecal
reduction
practices may have improved water clarity, but
initially seemed to be
and staff believed
algal density has increased, apparently because
their water quality goal had been reached. How-
of greater light penetration Monitoring data are
ever, saline concentrations strongly
fecal
highly variable. Factors such as desorption of
After adjustment of data for salinity
nutrients
bottom sediment and ground
levels through covariate analysis,
water or runoff contributions of soluble nutrients
levels had
decreased by 40% and personnel
were not addressed. After correcting for both
realized more dairies needed
precipitation and
there is no sig-
nificant trend over time.
Idaho, Florida, and Utah effectively
utilized upstream pollutant concentrations to ad-
is strong evidence that two dairy
just concentrations downstream of land treat-
(in
closures in the Otter Creek
to account for incoming concentrations.
September 1980 and 1986) in the Florida (Tay-
lor Creek
Slough) project resulted in
total phosphorus concentrations in
a decrease
Otter Creek and at the main discharge to Lake
Lesson: When sediment is a major
Okeechobee
the project area (Station
ant, at least some
sampling should
191). These dairy shutdowns resulted in a
be performed during high runoff periods
masking effect for evaluating impacts of
to avoid seriously underestimating overall
implemented
this tributary.
sediment loading.
completion of CM&E activities
Idaho RCWP project
the
RCWP project recommended
be-
additional field site monitoring because of the
lieved that significant sediment movement oc-
large amount of data needed to explain variabil-
curs in the
and that they may have
ity attributable to variables other than differ-
underestimated sediment loading by only meas-
ences in BMP implementation.
uring suspended sediment in the water column
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