Environmental Engineering Reference
In-Depth Information
Dry air or nitrogen
orifice gas supply system
High-
pressure
orifice
line
Low-
pressure
orifice
line
Solenoid
valve
Precision
differential
pressure
measurement
system
Solenoid
valve
Water
level
Atmospheric
reference
ρ = γζ
2
r = gζ
1
1
2
Water
temperature
probe
z
1
z
2
Orifice line
mounting
block
Upper
orifice
d
is distance between orifice
tube elevations = 304.8 mm,
+/- 1.76
Lower
orifice
d
-4
×
10 mm
Fig. 1.16
Schematic of the Double Bubbler Pressure Differential instrument.
Adapted from Larsen
et al.
(2001).
interest, particularly during high discharges that
occur more or less concomitant with the largest SSC
levels. Additionally, diel and storm-related fl uctua-
tions in water temperatures must be accounted for
by using a continuously logging temperature sensor
(the daily range in water temperatures at the Río
Caguitas streamgage is as much as 10 °C). The high
relative humidity characteristic of this humid-tropi-
cal site can also complicate the use of the Double
Bubbler because of the sensitivity of the narrow-
diameter bubbler gas lines to moisture, unless the gas
lines are equipped with dryer tubes. This test of the
Double Bubbler instrument showed the need for tem-
perature compensation, and possibly the need to
deploy the instrument at a site where weight densities
of higher fl ows might be substantially larger than
those measured at the Río Caguitas streamgage
during the Double Bubbler tests.
In 2004, the Puerto Rico Double Bubbler system
was transferred to the USGS streamgage on the Paria
River at Lees Ferry, Arizona, USA, and augmented
with a continuous water-temperature sensor. SSCs
near 10
3
g/L have been measured during storm runoff
at this streamgage. Deployment of the Double
