Assessing Water Footprint and Associated Water Scarcity Indicators: A Case Study of Concrete Manufacture

Water scarcity is a growing issue of concern across the globe. In recent times, a complex suite of water footprint impact assessment tools and concepts have supplemented traditional management approaches. A water footprint is a measure of humanity’s appropriation of fresh water in volumes of water consumed and/or polluted. There are several methods proposed in the literature to both quantify water use and assess its environmental impacts at defined spatial scales. In New Zealand, case studies in the water footprinting space are sparse, and are for the majority focused on the agricultural industry.

This research focuses on the building and construction sector in New Zealand, and takes a case study approach. The water footprints of 1 m3 ready mix concrete manufactured at 27 concrete batching plants throughout New Zealand were calculated and characterised by locally calculated characterisation factors to assess the environmental impact of water use for 1 m3 ready mix concrete at the catchment scale. The water footprint impact assessment methods of Hoekstra et al. (2011) and Boulay et al. (2016) are presented, calculating the WSblue and AMD characterisation factors, respectively.

The average volumetric blue water footprint of the 27 ready mix batching plants was quantified at 0.18 m3 (180 litres) of water per m3 of concrete, and ranged from 0.15 (150 litres) to 0.29 m3 (290 litres) of freshwater per m3 of concrete. In terms of their environmental impact, the water footprints of the Ashburton and Manawatu catchments post-characterisation, were found to have the greatest impact, based on the methods of Hoekstra et al. (2011) and Boulay et al. (2016), respectively.

The overarching goal of this research was to investigate how adaptable these globally developed methods are at the finer resolution in New Zealand. It is the aim that the findings from this research might aid water demand management strategies of New Zealand businesses. Furthermore, in recognition of the spatial complexity of water use, there is the potential for the development of a rating or marketing tool concerning the comparative water footprints of New Zealand products.