New tools to assess how seasonal snow contributes to streamflow in Aotearoa New Zealand

Summary of key findings

The snow that falls in the mountain regions of New Zealand is a major source of freshwater. The
seasonal snowpack that develops is unique as it acts as a natural reservoir of water in winter, which
is later released over spring and summer. Mountain rivers feed our largest hydro-electric power
schemes and provide critical water for irrigation, especially during drought. Given how vital water
resources are to New Zealand’s economic and social wellbeing, including their importance to Māori
and their communi􀆟es, it is imperative that we have the right tools to accurately assess the
contribution of seasonal snow to the water cycle.
To meet this need, this research has taken advantage of state-of-the-art observations of snow
obtained from satellites, as well as developing a new modelling framework to assess how much
snow is redistributed once it has fallen, to improve how the New Zealand Water Model handles
changes in streamflow in alpine catchments in New Zealand. The New Zealand Water Model is
currently the primary hydrological modelling tool being used to resolve how weather and climate
control streamflow at both the catchment and national scale.