This paper examines the water budget and surface energy balance of a Svalbard glacier (midre Lovénbreen) over a 6 year period (1997-2002). Fresh-water yields are found to lie between 1.1 and 1.5 m a−1 and reflect variable amounts of glacier ice ablation (0.27 ± 0.15 m a−1) and more consistent amounts of snowmelt and summer precipitation (0.40 ± 0.10 and 0.49 ± 0.12 m respectively). Between 24% and 36% of the annual runoff is thought to pass through a subglacial drainage system. Although the site is heavily influenced by stable maritime air masses during the summer, surface melting is achieved largely by net shortwave radiation fluxes (74-100% of ablation). Water budget analysis shows that the annual runoff yields may be strongly influenced by water storage within the glacial system. Storage can occur over the winter period and force the early development of the subglacial drainage system during the following summer. Thus annual water fluxes from this glacier cannot be estimated from glacial mass-balance data alone and there is a need to assess the implications of overwinter storage for our understanding of glacial dynamics, annual fluvial process rates and mixing processes in Svalbard's fjords.