Getting to the bottom of glacier lake – KU research boat on its first mission

Until now, Haas and his colleagues have mostly been on the glacier on foot. At regular intervals, they use a laser scanner and drone imagery to examine mountain slopes that are becoming unstable as the glacier's ice recedes. A radar device mounted on a sled is used to measure the thickness of the ice, which is rapidly decreasing due to high temperatures – the length of the Gepatschferner glacier recently decreased by just over 50 meters per year; no other glacier in the Alps is melting so quickly. In addition to exploring the glacier on foot, Florian Haas also regularly travels by helicopter. A laser scanner is mounted to the helicopter to also enable measurements of the terrain surface from the air.

The meltwater leaves the ice surface at its lower end at what is called the glacier gate. In the process, the stream also takes rocks and sediments with it and carries the material down the valley. "For our research on the landscape changes in the mountain massif and in the valley, it is also an important question how much gravel and finer sediments are carried away by the meltwater", explains Florian Haas. But, as the geographer points out, it was difficult to determine that directly on the glacial stream. A better opportunity is offered in the valley Kaunertal: There, below the glacier, is a water reservoir that was created about 60 years ago by building a dam to produce electricity for the region via a power plant. At the time of its construction, the dam was the tenth highest dam in the world, with a length of 600 meters and a height of over 150 meters, and the water depth of the lake is more than 100 meters in some places.

"Based on data and photographs, we know the terrain profile from the time before the construction of the Gepatsch reservoir and, following a new survey of the lake bed that is now being carried out, we can calculate the quantities of gravel and sediment that the glacial stream has transported into the lake since the water reservoir was commissioned and where the material has been deposited", explains Florian Haas. From this, an average annual sediment load can be calculated and also forecast into the future. He said this was not only an important missing piece for the SEHAG project, but also a useful finding for the reservoir's operating company.

In uniform paths – similar to a farmer with a tractor in the field – the KU research boat travels across the entire lake surface. On the screen, Florian Haas can read the information on water depth and can see on a map display which area of the seabed the echo sounder has covered. The technology could also be used for other research projects and locations; for example, surveys are planned in rivers close to barrages. "With this new equipment, we can work on issues related to, for example, the morphology, properties and changes in submerged parts of the Earth's surface." Thus, the KU research boat, which was previously used as a fireboat and was acquired second-hand, will be also used in other research projects.