Hydrology, sediment transport and water resources of Ammassalik Island, SE Greenland

A review and a synthesis of results from previous investigations are presented. New studies and results from the Mittivakkat Glacier catchment are used in an attempt to upscale results to other catchments on Ammassalik Island, SE Greenland. A snow-evolution modelling system. SnowModel, together with the hydrological model: NAM were used to simulate the water balance components for periods when direct measurements were not possible. The total annual precipitation (TAP) was 1,500 mm w.eq. y(-1) (1999-2006) for the whole Mittivakkat Glacier catchment, and 984 mm w.eq. y(-1) (1961-1990) uncorrected at the meteorological station in Tasiilaq (Ammassalik). The solid precipitation was 67.85% of the annual precipitation. Evapotranspiration was 250 mm w.eq. y(-1) sublimation during winter time was found to be 200 mm w.eq. y(-1) or 12% of the annual precipitation. The Mittivakkat Glacier has a negative mass balance in 9 out of 11 years (1995-2006); the average annual net loss was 700 mm w.eq. y(-1). This is the dominant change in storage in the area. Runoff from the Mittivakkat catchment was 1,970 mm w.eq. y(-1), the highl values are due to the negative mass balance of the glacier. Catchments without glaciers will have runoff values of approximately 1,200-1,400 mm w.eq. y(-1). Excess runoff due to the negative net balance from glaciers on the island is approximately 81* 10(6) m(3) or 120 mm w.eq. y(-1) from the whole island. The annual sediment yield from the Mittivakkat Glacier catchment is about 1,000 l km(-2) y(-1). Bed load is approximately 20% and suspended load is approximately 80% of the total sediment load. The dissolved load or yield is equivalent to 50 l km(-2) y(-1). Catchments without glaciers or with a large percentage of lakes will have sediment yields of around 10-50 l km(-2) y(-1) depending on surface material and slope. It is shown that the Mittivakkat Glacier is delivering approximately 30% of the total estimated sediment delivery from Ammassalik Island. Water supply for drinking purpose is plentiful. The water supply for the current hydro power production plant is sufficient to cover the present consumption, although about 10% of the flow stems from negative glacier net balance and flows could therefore change in the future.