Modelling snow and catchment processes

Understanding the seasonal snow contribution to streamflow in our largest catchments in New Zealand

The snow that falls in mountain regions in New Zealand is a major source of freshwater, but we still struggle to reliably estimate the amount of snow stored in our high alpine regions, how much water can be expected downstream and when it will be released. Mountain rivers in both the North and South Islands of New Zealand feed our largest hydro-electric power schemes, and provide critical water for irrigation, especially during drought. 

One of the most important tools currently available to resolve how climate controls streamflow in New Zealand is the New Zealand Water Model (NZWaM). It provides a sophisticated modelling framework to predict how much freshwater is available, where it has come from, and how quickly it moves through catchments in New Zealand. However, running a national hydrological model is not without its challenges, especially in New Zealand where there is so much diversity in local climate. One of the key challenges is understanding how snow accumulation makes a crucial contribution to many of our largest catchments.

We will engage with local authorities and iwi to determine the specific needs of communities that utilise water flows. This information will be used to target key sites and guide our efforts to generate detailed information about seasonal snow cover in our mountains using the latest generation of satellite imagery. These unique data sets obtained from observations from space and advanced numerical modelling of the redistribution of snow will be used to help reduce the uncertainty of modelling seasonal snow using the New Zealand Water Model. 

This will lead to an improved understanding of the climate processes governing the contribution of seasonal snow to the water cycle at both a catchment and national scale in New Zealand.

This project in the media:

• 17 June 2021: Newshub 6pm Current Affairs – Snow’s response to climate change the focus of new project 
• 18 June 2021: Otago Daily Times – Glacier melt most recorded
• 22 June 2021: RNZ Nights – Snow and our changing climate