This is the view looking north from the lake, up towards the Dobson Valley. The valley profile has the classic 'U' shape created by glacial erosion, and the flat valley floor is blanketed by sediments brought down by rivers, especially during floods when the water flows with high energy.
Here you can see the lake inlet. You can see the delta created as the sediments fill the lake.
Lake Ohau has been receiving a high level of scientific interest over the last few years, by scientists from GNS Science in collaboration with others from Victoria and Otago Universities.
|Gavin Dunbar of VUW preparing equipment|
A number of limnological (lake) measurements are being made to help understand the way water currents, water temperatures and water clarity vary seasonally in different parts of the lake. This is important because it allows for understanding of the factors that influence the deposition of mud on the lake floor.
In this photo Heidi Roop (GNS Science PhD student) is helping pull a sediment trap out of the water at the end of the lake nearest to the outflow. At the bottom of the trap there is a bottle of sediments that have accumulated over the last 4 months.
The 1 litre bottle is removed and replaced with an empty one. The bottle is quite full because it contains concentrated sediment that has fallen into the wide mouth of the trap. Careful recording is one of the most important parts of any scientific data collection.
Marcus Vandergoes and Heidi Roop prepare to lower a gravity corer into the lake to sample a small core of the top layers of sediment. As the corer penetrates about 25cm into the lake floor, the mud enters the plastic tube. A cap then seals the top end of the tube so that the mud is held in place by a vacuum as the corer is pulled back up to the boat.