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 are generating 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 are being 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:

• First rivers in the sky, now whiplash (Otago Daily Times, 2022)
• Snow’s response to climate change the focus of new project (Newshub 6pm Current Affairs, 2021)
• Glacier melt most recorded (Otago Daily Times, 2021)
• Snow and our changing climate (RNZ Nights, 2021)
• Snow models. Water flows. (He Kitenga, 2021)