 Global warming is expected to significantly affect the runoff regime of mountainous catchments. Simple methods for calculating future glacier change in hydrological models are required in order to reliably assess economic impacts of changes in the water cycle over the next decades. We propose a simple parameterization for calculating the change in glacier surface elevation and area which is mass conserving. This article was authored by M. Huss, G. Javit, D. Farinati, and others.