3/16/04

**Publication List Related to**

**Hydrological Instrumentation**

Publications and abstracts are listed in reverse chronological order. A
limited number of reprints are available, and can be requested by
referring to the NAEW number. Use your browser's "find" feature to
search for words of interest. For more information, please contact:

> James V. Bonta
>
> Research Hydraulic Engineer
>
> N. Appalachian Experimental Watershed
>
> PO Box 488
>
> Coshocton, Ohio 43812
>
> USA
>
> email: <bonta@coshocton.ars.usda.gov>
>
> phone: 740-545-6349
>
> fax: 740-545-5125

Bonta, J.V. and F.B. Pierson. 2003. Design, measurement, and sampling
with drop-box weirs. Applied Engineering in Agriculture 19(6):689-700.
**(NAEW #389)**

Abstract

Rangelands, surface mines, construction sites, unprotected and long
slopes, gullies, eroding stream channels, and erosion plots will yield
large sediment loads under high intensity rainfalls. Conventional
flow-measuring devices can easily become clogged with sediment and
debris during a major runoff event, resulting in the loss of runoff and
sediment records. Flow measurements can also be inaccurate using
conventional flow-measuring devices in steep channels. The drop-box weir
(DBW) was developed to overcome many of the problems encountered in
sediment-laden flow measurement. The weir creates turbulence in a box
that entrains and passes sediment through the weir. It is not a
well-known device, and it has not been widely used. Yet it is only one
of two devices suitable for obtaining flow records with large sediment
concentrations. It has utility for a range of watershed sizes from small
erosion plots to large watersheds. Information on what is known about
the design and operation of the DBW, and of sediment sampling approaches
using the DBW, was compiled. Weir sizing, rating-curve development, and
sampling strategies were presented to facilitate its use and to identify
its limitations. There are four known configurations of the DBW: the
original weir with upper weir lips; a modification of the DBW for
erosion plots (removal of upper weir lips); a modification of the DBW
for small watersheds in steep and skewed channels (removal of upper weir
lips and use of baffle); and a Korean version of the weir (larger chute
opening to minimize blockage of trash -- suitable for large and small
watersheds). For each of the four configurations, rating tables and
weir-sizing guidelines were summarized. Low-flow rating curves must be
developed from field data for individual weirs, but laboratory curves
can be used for larger flow rates. Curve-fitting procedures are outlined
specifically for determining rating-curve equations where field data are
obtained. Water samplers designed specifically for use with DBWs are
described. Other design considerations are discussed for practical use
of DBWs including measurement of stage, maintenance, and sediment traps.
Research needs for hydraulic modeling and sediment sampling are
presented.

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Malone, R.W., J.V. Bonta, and D. Lightell. 2003. A low-cost composite
water sampler for drip and stream flow. Applied Engineering in
Agriculture 19(1):59-61. **(NAEW #381)**

Abstract

The collection of flow-proportional samples when flow rates range from
slow drip flow to slow stream flow is important in hydrology. A rotating
slot sampler was modified for this purpose and its field and lab
performance were monitored. The major design criteria include: function
for flow rates between 0.5 and 200 mL/min (0.008 and 3.2 gal/h);
minimize sampler-fraction variance between trials; allow total flow
volume estimate from sampler-fraction volume; compact in size; useful in
remote conditions; low-cost; low-maintenance; and easily constructed
from readily obtainable materials. The designed sampler collected
approximately 2.0% of total flow (sampler-fraction) with a
sampler-fraction coefficient of variation between trials of less than
5%. The sampler allows total flow to be estimated and flow-proportional
samples to be collected.

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Bonta, J.V. 2002. Modification and performance of the Coshocton wheel
with the modified drop-box weir. Journal of Soil and Water Conservation
57(6):364-373. **(NAEW #379)**

Abstract

Water-chemistry, sediment, and runoff data from erosion plots and small
watersheds are often needed for erosion and water-quality studies where
sediment concentrations can be large. Data may also be needed under
conditions where approach channels are not appropriate for conventional
measuring devices, such as in steep and skewed channels. The performance
(sampler fraction) of the modified drop-box weir as the approach to the
Coshocton wheel proportional water sampler was evaluated to meet these
needs. Three splash-shield configurations on the sampling slot of the
Coshocton wheel were investigated to control splashing of water and
duplicate water sampling. Of the three shields, a dual-splash shield was
required to control water splashing below the sampling slot, and to
insure proportional sampling of large flows. The Coshocton wheel worked
well with the drop-box weir as the sampler approach uder steady and
unsteady flow conditions. The average proportional sampler fraction for
the dual-shield configuration under steady flows was 0.0127, and for
unsteady flows was 0.0120. This difference was not statistically
significant. Coshocton wheel rotational speed was regular and increased
with flow rate to about 35 rpm. After that, rotation became irregular
and the wheel stalled. No difference was found in a
maximum-depth-of-flow parameter needed for sizing a drop-box weir based
on sampler performance, compared with the parameter determined by
performance of the drop-box weir alone (i.e., the wheel sampled
proportionally at 100% of the design flow for the weir). This study
extends the utility of the combined drop-box weir and Coshocton wheel
system to steep and skewed channels.

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Bonta, J.V. and V.C. Goyal. 2001. Modified drop-box weir for monitoring
watershed flows under extreme approach channel conditions. Trans. Of the
ASAE 44(6):1581-1591. **(NAEW #370)**

Abstract

Flows under extreme weir approach conditions are difficult to accurately
measure, and occur when there are rapid flows, steep channels, skewed
flows in sinuous channels, and flows laden with sediment.  Building on
previous studies, the drop-box weir was modified and evaluated for use
in steep and skewed stream channels found in small watersheds. 
Modifications to the modified drop-box weir (MDBW) included preventing
water from overtopping the back wall of the box (forcing all water to
enter the sides of the box), extending the vertical side walls at the V
section of weir to preclude water flow out of the weir-measuring section
at high flows, and use of a channel baffle for energy dissipation. 
Three energy-dissipation configurations upstream of the box and 20
upstream approach conditions were tested.  The approach-channel angles
ranged from 0o to 45o, and approach-channel slopes from 5% to 75%.  The
investigations showed that an upstream baffle yielded a stable rating
curve compared with two other energy-dissipation measures.  Statistical
analyses of the rating curve parameters of the MDBW for each of the 20
approach conditions were similar, leading to the conclusion that the
rating was independent of approach channel angle and slope at all flows
when an upstream baffle was used to dissipate flow energy.   The rating
curve was composed of five linear segments on a log-log grid with
relative gauge-height (R = gauge height/depth of V notch of weir)
boundaries at 0.058, 0.11, 0.27, and 0.49.  Data suggest that departures
in the low-flow rating (R#0.27) between weirs may be due to differences
in weir fabrication, and field rating using the results and procedures
of this study are recommended.  Changes in the slopes of these linear
rating segments were associated with observed flow conditions in the
weir.  A maximum R of 0.63 was recommended for sizing a MDBW, but a R =
0.78 could be used if monitoring equipment had sufficient water-depth
resolution.  The rating curve developed in this study was nearly
identical to those developed in another independent study in which flows
were directed at a 90o approach angle by gutters, and also with part of
the rating curve of the original drop-box weir.  This suggests the
rating of this study is applicable to extreme approach angles beyond the
45º angle tested in this study. Guidelines for weir sizing and
developing rating-curves for the MDBW are given.

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Bonta, J.V. and V.C. Goyal. 2000. Comparison of drip-flow/low-flow
measuring devices for infiltrometer runoff measurements. Trans. of the
ASAE 43(6):1489-1498. **(NAEW #358)**

Abstract

Runoff is generated on landscapes in a deterministic and random, but
unquantifiable manner, and measurements of the spatial variability of
infiltration and seepage under natural-precipitation conditions are
highly desirable.  Runoff from small natural-precipitation infiltrometer
plots (0.25 m2) under natural conditions can be merely drip flows, or
they can be larger flows when runoff is produced simultaneously from 
high-intensity rains and seepage.  A study of a drip-flow/low-flow
nozzle/rotor flow-measuring system that met design requirements for
runoff measurement is presented.  Comparison of different nozzle
configurations led to the selection of the rotor of a Price current
meter, in combination with a unique nozzle that incorporated a drip
diverter, an internal flow baffle, and drip-control silicone beads.  The
best nozzle/rotor combination yielded a rating curve with a resolution
less than design requirements, and worked well with flows as high as \~6
L min-1, greater than design requirements.  A combined function using
linear segments for low flows, and a 4th degree polynomial for high
flows, comprised the rating curve.  The average residual error about the
function was 0.113 L min-1.    Unsteady flow tests with the nozzle
showed that the rating curve and nozzle/rotor assembly worked well, with
the median error in volume of -21 ml for 12  synthesized "events."  The
device is a standalone measuring system that can be placed anywhere on
the landscape, and only electrical pulses, representing rotor-rotation
speed require measurement.  The nozzle/rotor system can be used for
other applications in which drip and low flows need to be measured, such
as for rain gauges, percolation flows from lysimeters, spring flows,
etc.

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Bonta, J.V. 1999. Water sampler and flow measurement for runoff
containing large sediment particles. Trans. of the ASAE 42(1):107-114.
**(NAEW #344)**

Abstract

A flow-measuring and composite water-sampler system was needed for
sampling sediment-laden flows containing large rock particles from
strip-mine spoil erosion plots.  The median percentage of soil particle
sizes greater than 16 mm of the greater-than 2 mm fraction was 25%.  A
modified drop-box weir was used for measuring flows, and for providing a
well-mixed water and sediment flow that could be sampled.  A "diverter"
composite sampler was designed to divert the entire flow from a waste
position to a sample position, and precluded the need to subsample
(split) the sampled flows.   Indoor testing of the sampler showed the
sampler worked well with the modified drop-box weir.  Field evaluation
showed the sampler and drop-box weir worked well under natural rainfall
conditions. Recommendations for improvement in sampler and weir
operation are given. Use of the sampler for other applications is also
discussed.

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Bonta, J.V. 1998. Modified drop-box weir for monitoring flows from
erosion plots and small watersheds. Trans. of the ASAE 41(3):565-573.
**(NAEW #340)**

Abstract

Sediment-laden flow and chemical-constituent concentration data from
erosion plots and small watersheds are often needed for erosion and
water-quality impact evaluations and modeling.  The original drop-box
weir was modified to pass the design flow through the V-notch and box
sections of the weir.  Approach conditions consisted of gutters and
aprons that divert runoff water and sediment to the box at right
angles.  An evaluation of the effects of these approach conditions on
the original rating for the drop-box weir and the effects of not having
a false back wall for erosion-plot use was conducted.  A rating for low
flows was obtained.  The rating for the drop-box weir with the new
approach conditions was different from the original rating.  Three
rating equations were fit to the data simultaneously for the three flow
ranges.   Observations of weir performance suggested that the reason for
the three equations was related to the stepped side weirs.  This study
and other published studies led to the conclusion that the drop-box weir
should not be modified unless a new study of the effects of the changes
on the rating are evaluated.  The gage height for the design flow for
sizing the modified drop-box weir in small stream channels was
established. A decision table was developed for appropriate use of the
drop-box weir.

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Edwards, W.M., H.E. Frank, T.E. King, and D.R. Gallwitz. 1976. Runoff
sampling: Coshocton vane proportional sampler. ARS-NC-50. 9 pp. **(NAEW
#206)**

Abstract

This sampler collects a composited representative sample of runoff from
each storm event at sites where flow is measured by a broad-crested or
similar overfalling weir.  The sample can be used to determine average
concentrations and total transports of liquid and suspended solid
components of the runoff event.\
\
Proportionality is maintained by a revolving vane and movable outfall
that collect a consistent fraction of all runoff above a threshold or
base flow level.  Timer and double vane options provide for adequate
sample volume from large or small runoff events.  The sampler uses only
basic electrical and mechanical components and has performed well on
watershedsas large as 300 acres where the maximum design flow rate is
500 ft~3~/s.

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Bentz, W.W. and C.R. Amerman. 1968. A tipping bucket device for
measuring very low flows. Agric. Eng. 49(12):750-751. **(NAEW #153)**

Abstract

This paper describes the design and performance of a large tipping
bucket device that is used for measuring very small flow rates, such as
from spring flows.

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Parson, D.A. 1955. Coshocton-type runoff samplers. ARS-41-2. 15 pp.
**(NAEW #71)**

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Parsons, D.A. 1954. Coshocton-type runoff samplers, laboratory
investigations. SCS-TP-124. 16 pp. **(NAEW #65)**

Abstract

This paper documents the development of a modification of the original
Coshocton wheel sampler developed by W. Pomerene at Coshocton, Ohio. 
Principles of operation, performance data, fabrication information, and
installation guidelines are given.  This version of the Coshocton wheel
is used worldwide.

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