Maximising the benefits of desalinated seawater supply networks for agricultural sustainability (Funded by the QUEX Institute)

Globally, water stress is driving the replacement or augmentation of traditional freshwater supplies with desalinated seawater supplies. The unlimited supply of water provided by the sea, the relatively high population living in coastal regions, and prospects of cleaner and cheaper energy to drive the supply system are among the factors driving this trend. North Chile is perhaps the best example, with around 20 desalination plants recently constructed or in the pipeline. Globally, major cities, traditionally with abundant freshwater supplies, such as Sydney, Melbourne and London have invested in seawater supply to as a security against global climate change and population growth.

However, the contribution of seawater supplies to wider sustainability dimensions is poorly understood. One important dimension is small‐medium scale irrigated agriculture, since this traditional industry is central to many societies globally and contributes considerably to local and regional food security, yet it often lacks climate resilience. Irrigated crops rarely have the economic value that would permit unsubsidised purchase of seawater. This holds even under the most optimistic projections of costs and revenues. Nevertheless, water sharing schemes may be possible that provide sustainability benefits for agricultural and all other water users.

Research is needed to improve understanding of: the infrastructure and operational rules that would maximise value from an integrated and shared water supply system; the resilience to climate and other variabilities and uncertainties; and the trade‐offs necessary between the system’s multiple objectives. At present, although generic water supply cost‐benefit frameworks and models exist, none have been adapted and applied to exploring the role of seawater supplies in small‐to‐medium scale sustainable agriculture.

This proposed project will initially use the case study of the Atacama desert in Chile to explore the future role of integrated seawater and freshwater supply networks in arid regions. The project will focus on understanding the system, model development, optimisation and scenario analysis, working as part of a team of hydrologists, engineers, economists and social scientists investigating broader questions around arid region seawater supply. This case study is chosen as the one for which we already have rich data sets and where the described problems are of high importance.

The second case study area will be a semi‐arid region in north‐east of Brazil, where there is a great potential for solar‐energy powered desalination plants, which will bring a further sustainability dimension to this project.