BARWON RIVER ESTUARY 2016 and It Then Flows Through a System of Lakes to Meet the Ocean Between the Popular Coastal Townships of Barwon Heads and Ocean Grove
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The Barwon River Estuary is an environmentally significant and highly valued riverine estuary located in south-west Victoria. Its 19km length stretches from a tidal barrage installed in the year 1898 below the regional city of Geelong BARWON RIVER ESTUARY 2016 and it then flows through a system of lakes to meet the ocean between the popular coastal townships of Barwon Heads and Ocean Grove. The estuary is unique in the Date range: Corangamite region not only for its large size, but also 01/01/2016 – 31/12/2016 because its mouth is permanently open. The system of lakes incorporated in the estuary including Lake Connewarre, Reedy lake, Hospital Swamp and Murtnaghurt Lagoon. These wetlands form part of the Port Phillip Bay (Western Shoreline) and Bellarine Peninsula RAMSAR site. These lakes provide a wide range of aquatic The picturesque mouth of the Barwon River estuary from The habitats for native fish and birds. Bluff lookout. This brochure summarises 12 The estuary is a hotspot for recreation, popular for Type of Estuary: months of EstuaryWatch mouth swimming, fishing, canoeing, bird watching, game hunting, condition and physical and chemical Open Riverine picnicking, walking, motor and sail boating. data. Barwon River EstuaryWatch Location: -38.284329, volunteers monitor 3 mouth condition sites and 4 physical and 144.495908 chemical sites. In 2016 volunteers collected monitoring data for all 12 Nearest town: Barwon Heads months. Estuary length: 19.1km The Barwon River estuary is a permanently open estuary. The mouth condition River length: 156.6km photos and event photos taken in 2016 reveal a wide range of sand and tidal Threats to the Barwon River Estuary movements at the mouth of the estuary. The salinity results revealed site B1 Mouth state: – Threats linked to urban to be mostly sea water, by site B2 the water becomes more brackish, the most Permanently Open development such as stormwater upstream site B5 was mostly brackish with an occasional surface lens of run-off & degradation of native fresher water during times of higher river flow. Occasionally during summer, Description: The Barwon River is riparian and estuarine vegetation when river flows are low hypersaline conditions are present. No salinity the major river in the Bellarine stratification was evident in 2016. From June to early December salinity levels landscape zone. The Barwon River – Altered water regime were lower corresponding with increased river flows. During September high headwaters are in the Otway – Grazing pressures river flows flushed all salt water from the estuary. The dissolved oxygen levels Ranges and it flows over 150kms – Invasive fauna and flora throughout the estuary were maintained in the healthy range (median of all through the major regional EstuaryWatch volunteer training at Barwon Heads. sites and depths 89% saturation), the lowest level was recorded in the bottom township of Geelong. The estuary waters at site B5 (53% saturation). The water temperature ranged from 10°C commences downstream of a tidal in August to 22°C in March. barrage below Geelong and – Join the Barwon River EstuaryWatch Group EstuaryWatch records at the Barwon River estuary extend from 2007 and can finishes at the town of Barwon www.estuarywatch.org.au be viewed at www.estuarywatch.org.au Heads. – Join a local environment group such as Friends of the Bluff, Ocean Grove Coastcare or the Bellarine Catchment Network www.barwonbluff.com.au http://www.barwoncoast.com.au/ocean-grove- coastcare-inc – http://www.environmentbellarine.org.au/ – Share what you have learnt from this annual summary The Barwon River and Thompson Creek EstuaryWatch team. with a friend or family member. Corangamite Catchment Management Authority 64 Dennis St (PO Box 159) Colac Victoria 3250 (T) 03 5232 9100 (F) 03 5232 2759 Map of the Barwon River estuary, including the location of (E) [email protected] www.ccma.vic.gov.au EstuaryWatch sites. Sourced from Google Maps. For all four monitoring sessions chosen for the Estuary Snapshots, photo point photos and a longitudinal profile of the estuary from site B1 (At The Heads Jetty) to B5 (Taits Point) is displayed. The longitudinal profiles show the depth, salinity and percent saturation of dissolved oxygen (DO) at each monitoring site from the surface of the water column to the bottom. Not all sites were sampled on the same day (site B4 was generally sampled on the later date specified). Photos were also taken on different dates. Sampled Dates: 07-08/01/2016 Estuary mouth state: OPEN Photo Date: 29/01/2016 Sampled Date: 02-05/05/2016 Estuary mouth state: OPEN Photo Date: 04/05/2016 The Barwon river in flood on 18/09/2016. Turbid freshwater discharging through the river mouth at Barwon Heads. Photo courtesy of Steven Penman. On Friday September 16, the Barwon River discharge peaked at 17,098 million litres per day (recorded at the Sampled Date: 04/08/2016 Estuary mouth state: OPEN lower tidal barrage just upstream of the estuary). This Photo Date: 23/07/2016 high river flow was due to heavy rainfall in the Barwon catchment from September 9 – 14, rainfall over this period totalled 82mm, with rainfalls of 42mm on September 14 (recorded at Barwon Downs). The highly turbid river water originating from the north-western slopes of the Otways ranges takes several days to make its way to the estuary. These types of flows result in the flushing of all salt water from the estuary and restrict the tidal movement of sea water into the estuary. On Sampled Date: 01-03/12/2016 Estuary mouth state: OPEN discharging from the estuary mouth there is limited Photo Date: 01/12/2016 mixing of river water and sea water due density differences between sea water and fresh water. 18000 The daily discharge of river 16000 water in 2016 recorded at the 14000 lower tidal barrage upstream Southern Shortfin Eel, Anguilla australis 12000 of the Barwon River Southern Shortfin Eels pass through estuaries during several phases of their lifecycle. The adult eels 10000 EstuaryWatch site B6. spend up to 20 years in freshwater rivers, lakes and dams, before migrating to the sea to breed in the 8000 Coral Sea of north-east Australia. Following successful breeding the transparent leaf-like larvae are 6000 Data source: DELWP transported southwards via the East Australian Current, and grow into glass eels before migrating to 4000 Monitoring Station No. Discharge (Ml/day) estuaries in south-eastern Australia. Glass eels are often observed entering Victorian estuaries during 2000 233269 Barwon River U/S 0 lower barrage of Geelong their migration to freshwater, the young eels are able to climb barriers such as waterfalls and dam wetlands. walls. See more at: https://australianmuseum.net.au/southern-shortfin-eel-anguilla-australis Photo: A Southern Shortfin Eel, Anguilla australis, in the Morwell National Park, Victoria, 25 Oct 2015. Source: Matt Campbell / Bowerbird. License: CC BY Attribution .