The water supply to Longyearbyen:
Hydrology and hydrochemistry in Endalen
Endalen is delivering water to Isdammen - Longyearbyen’s only winter water source. Endalen is a snow, icemelt and rainwater-fed watershed with a moderate mining influence.
Glacial waters creating Endalselva are important for buffering and diluting contaminants from various mining outlets in the valley. However, as in Gruvedalen, the contamination is most pronounced at the end of summer when the glacier ablation is low and therefore unable to dilute inputs from the area influenced by mining activity.
Water quality is also influenced by the end of summer rainfalls that, when heavy, deliver contaminants form hillslopes.
Lastly, water quality issues were also associated with suspended sediment concentrations.
Suspended sediment transport in Endalen
The monitoring program in Endalen was designed to help reveal the sedimentation characteristics of Isdammen.
Automatic pump samplers installed for the duration of the summer collected water and sediment samples three times a day, while turbidity sensors were monitoring sediment transport every hour.
The results show a high sediment yield and a sediment transfer system that operates like in other small cold-based glacier basins.
There is no sediment delivery from beneath the glacier as a result of their cold-based temperature structure. Therefore the high concentrations are triggered by high water discharge and heavy rainfalls.
Other processes of sediment delivery are ground thaw and moraine mass movements responding to summer warming.
Since the glaciers in the valley were almost certainly more active at the turn of the 20th Century than they are now, the present day sediment transfer system is probably still adjusting to the changes that have occurred after 1900s.
Although high concentrations of suspended sediment are recorded in Endalen during high flows and heavy rainfalls, their concentration drops markedly between the valley and Isdammen inflow.
The storage of sediment in the Isdammen delta was found to be important and equivalent to 20% of the sediment influx to Isdammen during 2012-2013.
Lastly, during high rainfall and/or high discharge events, sediments are returned into circulation from the delta through resuspension causing high concentration of them in the lake.