A water quality survey was undertaken in December 2008 at two locations on the Western Australian Kimberley coast that were shortlisted as potential sites for the construction of an LNG processing precinct. Water samples were collected and processed to determine total suspended solids (TSS), chlorophyll a, b and c, ammonia, total phosphorous (P), total nitrogen (N), nitrate plus nitrite (NO3+NO2) and orthophosphate concentrations at selected sites across both study areas. The sampling program was designed to obtain a water quality snapshot of the early wet season.
Results indicate that chlorophyll a and c concentrations and total phosphorus concentrations were consistently higher in bottom waters at both sites, but highest at James Price Point. TSS concentrations in surface waters were found to be higher at James Price Point than at Perpendicular Head and total nitrogen concentrations were similar across all sites and depths.
As a result of this survey it was found that the default guideline trigger values from ANZECC & ARMCANZ (2000) for Australian tropical marine waters may not be relevant to the Kimberley region for chlorophyll a and total nitrogen concentrations, at least during the early wet season. In these situations the approach recommended in ANZECC & ARMCANZ (2000) is to derive site specific guideline trigger values using local reference sites or baseline data. However, fully characterising these waters would require a significant allocation of resources.
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