Quantifying water use in New Zealand's dairy food system: A baseline for future sustainability

Abstract

CONTEXT

In New Zealand, the dairy sector is a critical food system, contributing substantially to the nation's economy and supplying about 3 % of the world's dairy products. Despite this, a detailed assessment of water use across the sector has yet to be completed.

OBJECTIVE

This study addresses this gap by systematically quantifying blue (consumptive) and green (effective rainfall) water use in New Zealand's dairy sector up to primary processing.

METHODS

Using a regionally-specific approach, publicly available data were collected to calculate consented and actual water use for irrigation on dairy farms, and processing facilities nationwide. On-farm water use for stock drinking and milking sheds was calculated using region-specific values for irrigated and non-irrigated farms combined with the latest stock numbers. High-resolution climate data and land use data were combined to calculate green water use.

RESULTS AND CONCLUSIONS

In total, the dairy sector is responsible for approximately 20 % (2.46 billion m³ per year) of total consumptive (blue) water use in the country, over 90 % of which is driven by irrigation, and 80 % is sourced from surface water. Effective rainfall represents almost 80 % of total water use in the system (9.63 billion m³). Water use varies substantially across core dairy regions with consumptive water intensities ranging from 7.5 L/ha of dairy land in Canterbury to 0.15 L/ha in Waikato, despite both regions contributing majorly to the dairy sector.

SIGNIFICANCE

Understanding current water consumption and anticipating climate-induced changes are crucial for addressing the water supply-demand imbalance in New Zealand's dairy industry and ensuring the continued resilience of the food system. This work provides the most recent detailed estimate of the water quantity account, providing a platform for further analysis of the water dependence for the primary sector, comparison with other dairy-intensive countries, and more precise estimates for global studies on the water use of food systems and trade.