The Top End of the Northern Territory lies in the monsoonal zone and
receives rain during the November-April period. Initially, at the start of
the wet season, rain storms are localised, but, following the descent of the
monsoonal trough from below the equator, widespread rain occurs.
Overflow incidents at mine sites tend to arise midway through the annual
wet season when excess water accumulated in ponds begins to discharge
to the external environment. Remote-access monitoring may be undertaken at mine sites using
equipment to continuously measure water quality parameters with storage
of the information on a data logger. The data is then retrieved by visiting
the site and transferring it to a portable computer or by remotely
accessing the system using a telemetry system and transmission via
telephone, VHF/UHF or satellite. Such systems are readily available and
vary in cost depending on the sophistication of the data transfer system.
Available sensors for continuous monitoring include those for
conductivity, temperature, pH and other ion selective electrodes, eg
nitrate, and water level. Of these variables, conductivity is most useful
due to its inherent accuracy and stability of reading. Remote monitoring capability is able to provide: (i) more intensive
monitoring of key issues; (ii) more timely information; (iii) correct
perspective on the degree of environmental problem; and (iv) information
from remote locations, which would be difficult to monitor by more
conventional methods. Examples are given for applications of continuously logged
measurement of conductivity of waters discharging to drains and in
creeks at Pine Creek, Ranger, Nabarlek and Woodcutters mines in the
Northern Territory. These applications demonstrate the timeliness of the
continuous monitoring technique.