In-Situ Win-Situ 2000 Operators Manual - Manual (Page 43)

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DETERMINING DENSITY
The density of water in a well can be determined using an accurate tape
measure and a pressure transducer. A change in pressure is recorded
between two points as the transducer is lowered into the water and the
corresponding change in depth is recorded using the measuring tape.
Density is then calculated using a simple formula. This method is valid
if the pressure and depth measurements are accurate and the water
within the well is homogeneous throughout the entire depth of the well.
Note: Density can also be measured using a hydrometer if it is possible
to withdraw a water sample from the well. We recommend an accuracy
of ±0.0005
Procedure
There are two possible methods for measuring the change in water
depth. Choose the method that is the most convenient and accurate.
• Attach the tape measure to the transducer cable using an adhesive
(e.g., duct tape). The tape measure can be attached to the
transducer itself or to a segment of the cable that will be adjacent to
the top of the well casing. Read the cable positions directly from the
measuring tape. The measuring device must have a resolution of at
least 1 mm or 1/16 in.
• Alternatively, mark the positions of the cable with a felt tip pen. The
distance between marks is then determined with a tape measure
after the corresponding cable segment is removed from the well.
1. Lower the transducer into the well until it is submerged under about
one meter of water.
2. Secure the transducer at a fixed depth using the cable at the top of
the well casing. Wait an hour or so for the system to equilibrate.
3. Take an electronic pressure reading, manually, from the transducer
and record this measurement in PSI. This is measurement P
1
.
4. Read the tape measure relative to some fixed reference point (e.g.,
top of well casing) or mark the position on the cable with a felt tip
pen. This is measurement L
1
.
5. Lower the transducer at least three meters deeper into the water
and repeat steps 3 and 4. These are measurements P
2
and L
2
.
6. Density (
ρ
) in g/cm 3 is calculated using the following:
g x (L
2
- L
1
)
(P
2
– P
1
) x 6.894757
ρ
=
APPENDIX