cleared or saved in plastic bags for
Net sedimentation rate in ponds
is measured using a thin, rigid plas-
tic plate of about 30 cm square that
is pushed gently into the pond bot-
tom until the plate surface is flush
with the pond bottom surface. The
corners of the plate are secured by
aluminum tent pegs (Fig. 11 and 12).
Sediment in suspension settles onto
this plate, but this sediment can also
be reworked and resuspended by
wind or other mechanisms, thereby
delineating a net rate. Plates become
covered by sediment and aquatic
vegetation in 1 to 2 weeks.
Initially, in 1992, a stake with a
I ermanent Pond
millimeter-graduated scale on its
D termittent Pond
face was inserted into the pond bot-
tom, and the height of the pond bot-
tom and the water column were mea-
sured to provide a second tally of
the net sedimentation rate (Fig. 11a).
However, surface waves and glare
Figure 10. Pond sedimentation stations.
commonly made this a difficult mea-
surement to obtain. In addition, aquatic vegeta-
We measured the quantity of accumulated sedi-
tion on the bed commonly covered the base of the
ment to the nearest 0.5 mm by inserting a gradu-
scale. For these reasons, only water levels are
ated scale into the sediments at three places. Af-
measured on these scales.
ter measurement, the sediment in the cup is
Figure 11. Sedimentation station in a pond site. A meter stake (a), cup sampler (b) and
plate sampler (c) are shown in position. The plate sampler is located between the two