Grant M. Kopec

An integrated representation of the services provided by global water resources.

Water is essential not only to maintain the livelihoods of human beings but also to sustain ecosystems. Over the last few decades several global assessments have reviewed current and future uses of water, and have offered potential solutions to a possible water crisis. However, these have tended to focus on water supply rather than on the range of demands for all water services (including those of ecosystems). In this paper, a holistic global view of water resources and the services they provide is presented, using Sankey diagrams as a visualisation tool. These diagrams provide a valuable addition to the spatial maps of other global assessments, as they track the sources, uses, services and sinks of water resources. They facilitate comparison of different water services, and highlight trade-offs amongst them. For example, they reveal how increasing the supply of water resources to one service (crop production) can generate a reduction in provision of other water services (e.g., to ecosystem maintenance). The potential impacts of efficiency improvements in the use of water are also highlighted; for example, reduction in soil evaporation from crop production through better farming practices, or the results of improved treatment and re-use of return flows leading to reduction of delivery to final sinks. This paper also outlines the measures needed to ensure sustainable water resource use and supply for multiple competing services in the future, and emphasises that integrated management of land and water resources is essential to achieve this goal.

Visualising a Stochastic Model of Californian Water Resources Using Sankey Diagrams

This paper describes a novel approach to the analysis of supply and demand of water in California. A stochastic model is developed to assess the future supply of and demand for water resources in California. The results are presented in the form of a Sankey diagram where present and stochastically-varying future fluxes of water in California and its sub-regions are traced from source to services by mapping the various transformations of water from when it is first made available for use, through its treatment, recycling and reuse, to its eventual loss in a variety of sinks. This helps to highlight the connections of water with energy and land resources, including the amount of energy used to pump and treat water, the amount of water used for energy production, and the land resources that create a water demand to produce crops for food. By mapping water in this way, policy-makers can more easily understand the competing uses of water, through the identification of the services it delivers (e.g. sanitation, food production, landscaping), the potential opportunities for improving the management of the resource and the connections with other resources which are often overlooked in a traditional sector-based management strategy. This paper focuses on a Sankey diagram for water, but the ultimate aim is the visualisation of linked resource futures through inter-connected Sankey diagrams for energy, land and water, tracking changes from the basic resources for all three, their transformations, and the final services they provide.

Balancing the Needs of All Services Provided by Global Water Resources

Global assessments of water use tend to focus on the supply side, where data on physical hydrology provide an apparently (but often questionable) secure underpinning. However, one difficulty with this approach is that it struggles to deal with the issues of multiple uses of water and of treatment and recycling. Another is that global analysis offers little guidance to water policy and management, which invariably and necessarily act at more local scales. An alternative approach is therefore to evaluate demand for the goods and services offered by water, to both human beings and to ecosystems, and then to map these demands back onto resource flows. This paper describes the sources (precipitation, surface water and groundwater) and the uses of water in delivering all of its services (including its provisioning of environmental services), and uses two Sankey diagrams to visualise this system. The results stress the need for an integrated assessment of all water sources and services, simultaneously considering human and ecosystem needs, and highlighting the need to improve human water-use efficiency and productivity rather than lazily invading further the needs of ecosystems on whose additional services humans rely.