Wellstead Estuary

	Wellstead Estuary at a glance
	Estuary area:		2.5 square killometres
	Average annual rainfall:		600-700 millimetres
	Lower estuary volume:		2.4M cubic metres
	Estuary length:		13 kilometres
	Annual flow from Bremer River:		2.7M cubic metres
	Data selection
	Stories of the Bremer River and Wellstead Estuary (450K PDF file)

      

The inlet is relatively shallow, less then one metre deep, with high evaporation. Salinity varies from one third to about twice that of sea water, making it an unfavourable environment for most marine animals and plants. Marine fish and invertebrates enter when the bar opens, but most do not survive long in the high salinity and there can be catastrophic mortality of the fauna, although this is infrequent.

Observed surface temperatures range from 12 °Celsius in winter to 25 °C. in summer. There will often be a temperature gradient along the length of the estuary with warmer water in the shallow basin and colder water in the riverine reaches. When the water is stratified, surface and deep water temperatures may differ by several degrees.

Surface water is generally well oxygenated, but when the water is stagnant or stratification is prolonged, there will be some degree of deoxygenation in water below the halocline.

Wellstead Estuary appears not be to eutrophic, probably because of the abundant growth of sea grass Ruppia, and other water weeds that utilise excessive nutrients in the system. The limited data suggests that nutrient levels are low, and there is no evidence of pollutants entering the estuary, but runoff from the town roads following rain may contribute undesirable amounts of oil to the stagnant estuary.

The Wellstead Estuary is reported to have been closed for as long as twenty years between 1860 and 1880 (it was closed for seven years in the 1970s), and will only open after heavy rain. The length of time the bar stays open varies once it has been breached. It usually stays open for several months, but it may remain so for years. The combination of a small catchment area and the closed bar causes the lagoon water to become stagnant.

There is a small permanent population, with seasonal influx of visitors to holiday homes and caravan parks.

Further information:

Estuaries and Coastal Lagoons of South Western Australia: Beaufort Inlet and Gordon Inlet. Environmental Protection Authority, Perth, Western Australia: Estuarine Studies Series Number 4 November 1988.

South Coast Regional Land and Water Care Strategy: The Fitzgerald-Biosphere Sub-region. Prepared by the South Coast Regional Assessment Panel and the South Coast Regional Initiative Planning Team March 1997.

Estuaries and Coastal Lagoons of South Western Australia: Wellstead Estuary . Environmental Protection Authority, Perth, Western Australia Estuarine Studies Series Number 4 November 1988 Number 1 June 1987.