Orifice Discharge Monitoring; Artesian Monitoring - Solinst Levelogger Series User Manual

Levelogger User Guide - Software Version 3.2.3 or Higher

Orifice Discharge Monitoring

Discharge through orifices such as in a Hickenbottom perforated riser is a
common water detention and flow control approach. The Hickenbottom device
typically uses a series of circular holes drilled both around the circumference
and along the vertical length of a section of riser pipe connected via an elbow
joint to a lateral discharge pipe. Hickenbottom devices are commonly used to
detain stormwater in ponds, wetlands, ditches, swales or depressions at the
Hickenbottom riser to reduce downstream erosion and prolong the settling
period for suspended solids prior to discharge thereby improving water quality.
Hickenbottom devices enable the practitioner to derive discharge rate by head
measurement outside the structure. Discharge from a Hickenbottom structure
can be calculated as the iteration of individual single orifice discharge equations.
A typical orifice equation is derived from Bernoulli's equation and can be
written as follows for metric units:
Where:

Artesian Monitoring

Monitoring of artesian conditions in which the piezometric surface is above
ground surface or more particularly above the top of well casing elevation using
Leveloggers can be quite straight forward. Three artesian scenarios are
discussed: a) continuous artesian conditions where i) freezing is not a concern,
ii) or where freezing is a concern and b) intermittently artesian conditions.
Continuous artesian conditions infer that the piezometric surface never drops
below the level the ground surface or particularly the top of casing elevation and
the casing is sealed with a sealed wellhead. In this case, where freezing is not a
concern, the Levelogger need only be installed in the wellhead itself by means
of a large compression fitting as illustrated in Figure 10.7. Solinst can supply a
7/8" nylon compression fitting for this purpose. First, a 7/8" NPT hole is
tapped into the wellhead, then the base of the compression fitting is threaded
into the hole and the threads sealed. The collar and ferrule are slid on the
Levelogger just above the transducer measurement line (collar below ferrule),
the logger inserted in the base and the nut slide down over the body of the
logger. The nut is tightened and threads sealed to form a hydraulic seal against
the body of the Levelogger leaving the upper portion of the Levelogger and cap
exposed above the compression fitting. The user can communicate with the
logger simply by removing the logger cap and attaching the Optical reader.
Ensure that the logger and sealed wellhead are enclosed within an outer
protective well cap or enclosure.
Q = CA(2gh)
Q = Orifice discharge in m
C = The discharge coefficient (C c C v ≈ 0.647), where C c ,
the coefficient of contraction, for a sharp-edged
orifice is ≈ 0.66 and C v , the coefficient of velocity
through the orifice is ≈ 0.98.
2
A = Orifice area in m
g = Acceleration due to gravity (9.81 m/sec
h = Head in m of water above the orifice
0.5
3
/sec
2
)
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