Five sites were sampled on the Gairdner River; they are shown on the map above. Photographs are available for each site:
The temperature of the water at the sites ranged from 14.79 to 19.61°C.
Salinity decreased down the river from above seawater at 50.2ppt at the most upstream site (GAI04) down to 17.3ppt at the lowest site GAI01. Nyerilup Creek site was 30.45ppt which is just below seawater at about 35ppt. The site on Calyerup Creek was much fresher with a salinity of 7.83ppt.
The acidity ranged from just below neutral at pH 6.6 in the main channel to pH 8.98 which is more basic at the site of Nyerilup Creek.
For total phosphorus, sites GAI02 and GAI05 had the highest levels with 210 µg/L and 98 µg/L respectively. The remaining three sites had lower levels between 20 and 34 µg/L. Total nitrogen concentrations reduced as the sites went downstream. The highest level was recorded at site GAI05 with 2500 µg/L. The lowest concentration was recorded at the lowest site GAI01 at 990 µg/L.