Derwent Estuary Ambient Water Quality monitoring program.

Updated: 2024-03-26

Since 2003, ambient water quality monitoring has been carried out on a monthly basis at up to 28 sites throughout the Derwent estuary by Norske Skog Boyer, Nyrstar Hobart and the State Government (EPA/Derwent Estuary Program-DEP). Monitoring is carried out by three different boat-based sampling parties, but is co-ordinated to occur on the same day each month. At each site, in-situ field measurements are taken using calibrated sensors for temperature, salinity, pH, dissolved oxygen and turbidity. Water clarity is also measured using a secchi disk. Surface and bottom water samples are collected for analysis of true color, total suspended solids(TSS), total and dissolved nutrients, organic carbon and zinc. At most sites, depth integrated samples are also collected for chlorophyll a using a plastic tube. In the middle and outer estuary , surface samples are collected by hand, while bottom samples are collected using a Niskin bottle. Pumps are used in the upper estuary site to fill up the bottles. All water samples are analysed at Analytical Service Tasmania, a National Association of Testing Authorities-accredited laboratory. A complete description of the program is available in the "State of the Derwent Estuary 2009" report as well as on the DEP website (links below).