Many of the state's aquifers are already stressed because of
high rates of water extraction and increasing salinity. Water
table aquifers are particularly susceptible to these pressures
waters, although leaky wells are also a potentially significant
pathway for pollution of deeper confined aquifers.
Elevated nitrogen
(mainly in the form of nitrate)
concentrations have been detected in all of the EPA groundwater
monitoring programs across the state. Further work is required
to determine whether this pollution is localised to a well or
represents broader influences. Elevated nitrate in groundwater
may restrict its use for drinking. This is because nitrate can
be toxic at the concentrations detected in some wells. Nitrate
may also adversely affect groundwater ecosystems or surface water
ecosystems that are fed by groundwater.
Heavy metal concentrations above national guidelines for ecosystem
protection have been found in several of the state's key aquifers.
However, it is most likely that these metals are naturally occurring
because of local geology and are therefore unlikely to be a threat
to ecosystem health.
A review of EPA groundwater monitoring programs in the Willunga
and Northern Adelaide Plains (NAP), Barossa Valley and Eyre Peninsula
aquifers indicated that water quality in all aquifers has been
influenced by nutrient pollution. As yet however, no trends have
been identified.
The pollution of aquifers with very high ammonia, nitrate and
nitrite concentrations compromises irrigation, drinking water
supply and ecosystem values. The detection of high nitrogen concentrations
in the confined Northern Adelaide Plains aquifers, together with
the detection of pesticides in other regions, indicates potential
seepage down poorly constructed or maintained wells. Further investigations
are required to assess whether the impacts are localised to the
monitored wells or representative of broader pollution problems.
Introduction
