Runoff Samplers
USDA Coshocton-Type Runoff Sampler
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The Coshocton-type runoff sampler is constructed to form a
single unit with the small H flume. Three basic models, N-1, N-2
and N-3, have been designed for use with the 0.5, 1.0, and 1.5
foot (15.2, 30.5, and 45.7 cm) H flumes. Models N-1 and N-2 have
been used extensively in the field. A typical field installation
is shown.
Sampler size and capacity for a given experiment are determined
by the capacity of the H flume required to measure peak runoff
rates. Slightly oversized flumes and samplers are recommended
because the sampling error increases significantly at discharges
above 80 percent of flume capacity. For small plot studies the
maximum runoff rate is assumed to equal the maximum expected
5-minute rainfall rate. Sample storage capacity is provided for
the aliquot sample from the maximum 48 hour runoff event.
Water discharge from the H flume falls on the water wheel,
which is inclined slightly from the horizontal, and causes the
wheel to rotate. An elevated sampling slot mounted on the wheel
extracts an aliquot sample as the slot traverses the flow jet with
each revolution of the wheel. The sample is routed through the
base of the wheel to a sample storage tank.
407-001 N-1
Coshocton Sampler 60 lbs.
407-002 N-2
Coshocton Sampler 75 lbs.
407-003 N-3
Coshocton Sampler 90 lbs.
Gerloch Trough Runoff Sampler
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In the study of sediment yield with different kinds of land
use, Gerloch troughs of various designs have been used. Gerloch
troughs capture surface runoff and channel the slurry into a
sealed bucket that is used to document sediment yields from
unbounded plots. These have been used extensively by the USGS in
Puerto Rico with excellent results. The trough is an aluminum
channel 20" long with a 3/4" hose connection for collection in a 5
gallon utility bucket. The top of the trough has a galvanized
sheet metal rain cover. Installation consists of digging an area
the width and length of the trough, creating a slight slope in the
direction of the runoff hole. Insert the trough, anchoring the
2-inch lip in the soil. Backfill the area under the trough; then
connect a clear nylon hose to the trough's hose barb.
Place the bucket far enough downhill to prevent backup into the
drain line. If a large amount of precipitation is anticipated, an
additional drainhole can be installed above the first drainhole
with runoff into a 2- or 5- gallon bucket.
407-050 Gerloch
Sampler 8 lbs.
407-051 3/4" PVC
Hose - 10 ft. 0.4 lb.
507-187 5 Gallon
Utility Bucket 0.5 lb.
