Lake Wollumboola is the largest shallow saline lagoon in southern NSW. It is one of approximately 90 coastal lakes in NSW formed following the last Ice Age. During this time the melting of the ice caps caused the sea level to rise and flood coastal river valleys. In some of these flooded valleys, the wind and waves built up sand barriers forming coastal lakes and other wetlands.
The diverse habitats of Lake Wollumboola provide a significant over-wintering ground for migratory shorebirds and a drought refuge for waterbirds. More than 30 protected migratory bird species use the lake. It regularly houses more than 1% of the world's population of Black Swans. Other species including the endangered green and gold bell frog can be found along the lake shore. The lake also has special cultural significance for the Jerrinja Aboriginal people.
Lake Wollumboola is usually closed to the sea by a sand barrier that forms on the eastern shore of the lake. The lake level rises and falls in response to how much rain or runoff is collected in the catchment or lost through evaporation. After prolonged heavy rainfall, rising lake levels put pressure on the sand barrier. A natural opening of the lake occurs when the sand bar is breached by water, usually at high tide under storm conditions. Outrushing water forms a channel to the sea and the lake level will drop. Eventually wave action deposits enough sand in the entrance to close it again.
This cycle of opening and closing occurs naturally. It is also possible for a man-made channel to be created to open the lake to the sea artificially. In the past this has been performed illegally and incorrectly, notably in 2006 and 2011, causing the death of thousands of fish. However, if the lake is at risk of flooding inland and threatening people or significant assets, the authorities may perform a controlled opening of the lake to the sea.
To complete this Earthcache you must visit the area and perform some observations, read the available info and answer the following questions:
1. At WP1 (the published coordinates) there is an information shelter. There are also smaller information signs as you walk along the path to the observation platform. According to these signs, how long does it usually take for wave action to rebuild the sand barrier?
2. What would be a valid reason for the lake to be artificially opened to the sea by a man-made channel?
3. Standing on the observation platform at WP2 (S 34° 56.365 E 150° 46.521), look South-East towards the sea. If the lake is closed, you will see a solid strip of sand between the lake and the sea. If it is open, you will see a channel joining the two bodies of water. At the time of your visit, was the lake open or closed to the sea?
Please email your answers to me via my profile link. You may post your Found log immediately without waiting for my response. I may not contact you unless I feel your answers require clarification. If I don't receive correct answers within 7 days of your Found log being posted, I may delete your log. Please don't post answers to the questions above in your log.