Chapter 3 ________________________________________________________________ Installation
VAISALA ________________________________________________________________________ 51
The QMT107 probes are pressed into pre-formed holes, but they can
also be placed into excavated holes that are then filled. On hard or
rocky ground, a pilot hole is pre-formed with an auger rod.
Soil Moisture
The soil water content measured by the ML2x sensor within one small
locality can be affected by:
- Variations in soil density and composition
- Stones close to the rods
- Roots (either nearby or pierced by the rods)
- Earth worm holes or mole holes
- Subsoil drainage
- Small scale variability in transpiration and evaporation losses.
It is important to take the degree of variability of these parameters into
account when deciding on the number of probes to be used at any
particular location. If the soil is known to be very heterogeneous, it
will be necessary to take measurements from at least three closely-
spaced locations.
Water Level
Place the QMV101 and QMV102 sensors according to the following
examples. Refer to Figure 33 on page 52.
Example 1: Average water level is 25 meters and maximum annual
change is 50 cm. Suitable sensor is with range of 75 cm and
installation place is 24,6 meter from ground level.
Example 2: In dry season the riverbed is dry and in rain season the
ultimate water level is 7 meters. Suitable sensor would be with 10-
meter range. If interested values start after water level is greater than 3
meters, it is possible to use 5-meter version and install it to 3 meters
from ground.
