Rapporten - Søren Højmark Rasmussen

English summary
The municipality of Aalborg plans a groundwater extraction from Volsted Plantage. The
purpose is to supply the citizens of the municipality with 1.000.000 m 3 drinking water
pr. yr. The object of this paper is to estimate the influence this extraction will have on
Hølbækken, a nearby brook. Hølbækken is classified as a salmon habitat. This means
that the median of the annual minimum flow in the brook can only be affected
minimally.
The project area was interpreted by making a conceptual model, in which the geology,
hydrology and hydrogeology of the project area was investigated. On the basis of the
conceptual model a numerical groundwater model was developed. The groundwater
model was generated using GMS 5.1. Two different geological interpretations of the
model area and two different placements of the extraction wells in Volsted Plantage
were simulated using the model. The different calculations and placements produced
similar results. The calculations showed a 20 % decline of the water flow in Hølbækken
when 1.000.000 m 3 /yr was extracted. The water flow declined by 10 % when 500.000
m 3 /yr was extracted. This paper concludes that the planned extraction of 1.000.000
m 3 /yr influences the water flow in Hølbækken by more than the accepted according to
the salmon habitat classification.