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# Calculating the energy potential

In order to be able to assess the size of a hydroelectric power potential, you must have knowledge of the runoff of water from the lakes that collects melt and rain water from surrounding mountains and the inland ice sheet.

Asiaq - Greenland Survey - operates hydrological measuring stations on many of the most important hydroelectric power potentials in Greenland and measures, among other things, rainfall and water levels. Based on data from the measuring stations, it was calculated how much water runs through the lakes during a year.

• The lake's surface area was measured and the water depth was studied with sonar, so you can calculate how much water the lake holds. At the same time, a place was sought with as deep water as possible for the location of the intake to the tunnel to direct water to the hydroelectric power plant through.
• The possibility of damming the lake (raising the possible water level) is a very important factor to increase the lake’s maximum amount of water and thus increase the capacity.

Dams also increase the water drop. Thus, achieving a better energy utilisation of the amount of water in the lake.

The above studies are prior to any construction of hydroelectric plants, and it is important to be aware of the possible fluctuations in rainfall and meltwater from year to year. If the weather is cold and rainfall is poor one year, this can result in a hydroelectric power plant running on reduced power in order not to empty the reservoir lake for water during the winter. This risk can be counteracted by ensuring that the best reservoir lakes have sufficient capacity to withstand an extended period of low flow.

A hydroelectric power plant extracts the energy out of water movement by allowing fast flowing water to drive a turbine. The turbine produces electricity that can be sent over long distances to places where the electricity can be utilised. The amount of power produced is adjusted by increasing or decreasing the water to the turbines.

To ensure that the predictions on future of water levels in the power plant lakes is as accurate as possible, it is important to have data from many years of measurements when calculating the power potential and planning the construction work. The measurements made today may therefore prove to be an important contribution to decisions on hydroelectric power plants in 20 years. For individual lakes, among others, Tasersiaq, Greenland Survey has hydrological data that stretches back to the mid-1970s.