WfHC - cover page (not to be used with pre-printed report ... - CSIRO

Figure 92. Oblique air photos of Horseshoe Lagoon looking East.
4.3 Water quality
Section 4.1 discussed human and animal activity and distribution, and Section 4.2 focused
on processes affecting water volume and sediment load in key lagoons. Both of these issues
are potentially significant to station water quality in general, and to water quality in those key
lagoons in particular. Information in Section 2.2.5 and elsewhere suggests that water quality
is impacted by a range of factors including:
Increased sediment loads in water caused by landscape processes (erosion, fire,
grazing, etc.)
Turbidity caused by animal activity directly in or adjacent to water (including large
terrestrial animals like pigs and cattle, as well as naturally occurring turbidity caused
by aquatics);
Larger dead animals in or adjacent to the water (either naturally occurring or
deliberately shot);
Sediment or chemical inputs from human activities (most significant for the
homestead, cattle yards, roads close to lagoon banks or inlet or outlet channels, etc.);
Oriners cattlemen referred to Oriners Lagoon water being „milky‟ in the past, particularly in
the late dry season (but that floodwater ran clear in the wet). Clearly there is a natural
sediment load in the system, but seasonal increases in this load do not render lagoon water
undrinkable (or pose immediate risks to aquatic species). This „milky‟ appearance late in the
dry season is likely a result of the suspension of small clay particles (colloidal clays with
electric charge) that do not readily settle out. This is largely a natural phenomenon, but could
be enhanced by excess clay sediment delivered to the lagoon from land-use impacts. More
significant water quality risks to the major lagoons lie from inputs by humans and larger
animals. More frequent and extended residence at Oriners increases the need for adequate
water quality, but also increases the chance that the immediate risks to quality can be better
managed. A model for water quality will not be produced here, but it remains a relevant issue
in a synthesis focused on the implications of greater human residence and on the volume
and status of key permanent lagoons.
Working Knowledge at Oriners Station, Cape York
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