Scientists at Plant & Food Research have calculated the water footprint of New Zealand’s hydroelectric power stations and found that, in most cases, the water footprint is only slightly positive or even negative. The research also showed that the dam and reservoirs associated with hydropower stations in high rainfall areas of the North Island do not adversely affect the amount of water available for use downstream.

Calculating production footprints provides consumers with a measure of the environmental impact of the plant and food products they buy. Fresh water is one of the most valuable resources globally, for drinking and irrigation, and consumers are increasingly demanding products made with economical water footprints. For producers, these water footprints provide a means to reduce costs by identifying areas in the production lifecycle where efficiency measures can be applied.

Research by PhD student Indika Herath in Dr Brent Clothier’s Systems Modelling Group at Plant & Food Research has measured the water footprint of hydropower generation at 17 hydroelectric stations across New Zealand as part of a research project to calculate the production footprints of New Zealand’s plant and food products. The research, published in the Journal of Cleaner Production, shows that the water footprint of hydroelectricity generated in New Zealand is lower than the international figure routinely used. In the North Island, hydroelectricity generation has a negative water footprint, with the presence of a reservoir not decreasing the amount of rainwater entering downstream river systems.

“Water is a necessity for life and the growing population is putting increasing pressure on this vital resource for human use, industry and agriculture,” said Dr Clothier. “It’s important that we reduce water use wherever possible and developing water footprints for each step of a production life-cycle is one way to help us accomplish this, allowing us to assess hot-spots of water use and economise where possible.

“Electricity is a key component of any food product’s environmental footprint, used in powering irrigation and other systems on the farm, through to packaging, processing and storage of finished goods. Whilst greenhouse gas emissions and the carbon footprint of hydroelectric power is smaller than that of most other fuel types, international evidence suggests that it has a larger water footprint. Our research shows that New Zealand hydroelectricity has a much lower water footprint than the global average. With more than 57% of New Zealand’s electricity generated through hydropower stations, this low water footprint for power generation reduces the water footprint of our products and reflects our brand image of ‘clean and green’.”