Monitoring Program Design
Subwatershed
Monitoring a subwatershed by taking samples close to pollutant sources and
treatment can be useful for observing the aggregate effect of implementation on
offieldsorseveral farms. Subwatershed monitoring networks measure the
aggregate effects of treatment and nontreatment runoff as it enters an upgradient
tributary or the receiving water body. Subwatershed monitoring can also be used
for targeting critical areas.
Paired subwatersheds are often monitored when tightly controlled experimental
conditions are desired. A pre-implementation hydrologic calibration monitoring
survey
to three years may be required. Each watershed is monitored in order
to develop a precipitation-runoff model to estimate its relationship with hydro-
logic response and pollutant export.
Watershed
Monitoring at the watershed scale is appropriate for assessing total project area
pollutant load using a single station. Depending on station arrangement, both
subwatershed and watershed outlet studies are very useful for water and pollutant
budget determinations. Monitoring at the watershed outlet is the least sensitive of
the spatial scales for detecting treatment effect. Sensitivity of the monitoring
program decreases with increased basin area and decreased treatment extent or
both. In addition, nontreatment effects such as hydrologic variability and
nonhomogeneous land use increase MDC.
Monitoring comparable treatment and control sites is an important feature in a
monitoring design. Monitoring a control site provides the data to separate the
Reference Sites
impact of treatment from the variability shared by systems. One option is to
monitor
stream stations in similarly paired watersheds--one in which there
is a management action and the other, without. Likewise, a survey of treated and
reference lakes may be used to show treatment effects. Implementation can be at
the same time or staggered through time to track and account for factors (e.g.,
climate) that affect all lakes at once.
Monitoring comparable
Using one or more reference sites can account for biological or habitat variability,
treatment and control sites
therefore reducing the time needed to detect improvement and providing stronger
is an important spatial
statistical evidence of cause-effect. Disadvantages include expense and the
difficultyoffindingareferencesimilarinmost featuresexcept forimplementation
feature in a monitoring
and the need for coordinated monitoring in both systems.
design.
The reference site should be part of an ecosystem with the best attainable habitat
and biological components (Plafkin et al. 1989). Reference system conditions
should be similar to the treated area in almost every respect except for the
reference and the treatment system should be in
ecoregion
and their watersheds should have similar geography, soils, and land use. Best
professional judgment should be used to determine if the ecosystem to be treated
has the potential to achieve the quality of the reference ecosystem.
Streams and Rivers
For monitoring streams or rivers, a paired or an upstream-downstream configu-
ration of a network or a control and treatment station should be considered. Both
streams should have similar land use, be of
order, have similar hydrologic
regime, and be close enough to have approximately the same rainfall.
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