The impact of urban groundwater upon surface water - eTheses ...

MONITORING NETWORKS AND METHODS
Difficulties were encountered in seating the meter to a suitable depth (10 cm) in coarse gravel
bed sediments, and high river flow induced errors in the seepage measurements as found by
other workers (Libelo et al 1994, Isiorho et al 1999). The seepage meter did not permit the
direct sampling of groundwater quality from depths below the groundwater and surface water
interface (10cm). Emphasis was therefore placed on the riverbed mini drivepoint piezometers
to be developed as the primary tool for the investigation.
4.9.2.1 Construction of a seepage meter
Seepage meters were constructed according to the basic design of Lee (1977) from 200 litre
oil drums cut in half around the circumference. A 12 mm diameter hole was drilled in the
top/base of the drum and a water tight cable gland installed (Figure 4.7). A 40 cm section of
LDPE tube was inserted into the cable gland and sealed in place. The seepage meter was then
driven to a depth of 10 cm within the river bed sediments. An attempt was made to remove all
air bubbles from the meter before attaching a plastic food bag filled with 100 ml of water and
no air. The bag was attached to the end of the LDPE tube with the aid of a rubber band. At the
end of the sampling period the bag was emptied into a measuring cylinder and the new
volume recorded.
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