Seven years of snow cover monitoring with MODIS to model catchment discharge in New Zealand

MODIS/TERRA was used to monitor the snowpack dynamics in the Waitaki catchment, New Zealand, from 2000 to 2007. Daily meteorological data (i.e., temperature and precipitation) and frequent observations of the snowpack were used with the Snowmelt Runoff Model (SRM) to simulate the daily discharge of the Ohau, Pukaki, and Tekapo catchments. The results obtained over these seven years brought considerable improvements in terms of modelling performances compared to previous efforts conducted in the region. It shed new light about the relative contribution of snowmelt to the discharge. The simulations also suggest that the severe drought of 2005 was largely mitigated by ice melt from glaciers in the Pukaki basin. A contribution of glacier melt much larger than normal is believed to have sustained the discharge to within 17% of the mean annual flow, although the precipitation was reduced by 34%.