Metrics of water scarcity and stress have evolved over the last three decades from simple threshold indicators to holistic measures characterising human environments and freshwater sustainability. Metrics commonly estimate renewable freshwater resources using mean annual river runoff, which masks hydrological variability, and quantify subjectively socio-economic conditions characterising adaptive capacity. There is a marked absence of research evaluating whether these metrics of water scarcity are meaningful. We argue that measurement of water scarcity (1) be redefined physically in terms of the freshwater storage required to address imbalances in intra- and inter-annual fluxes of freshwater supply and demand; (2) abandons subjective quantifications of human environments and (3) be used to inform participatory decision-making processes that explore a wide range of options for addressing freshwater storage requirements beyond dams that include use of renewable groundwater, soil water and trading in virtual water. Further, we outline a conceptual framework redefining water scarcity in terms of freshwater storage.Electronic supplementary materialThe online version of this article (doi:10.1007/s13280-017-0912-z) contains supplementary material, which is available to authorized users.

Water and wastewater tariffs constitute a primary avenue for utilities to generate revenue towards covering the costs associated with water and wastewater service provisions. In the pursuit of achieving global access to safe and affordable water and sanitation, utilities and governments play an important role in regulating and setting combined tariffs, so that they are able to fund the necessary infrastructure while at the same time ensuring that tariffs do not impede on the ability of consumers to access these services. From a survey of 568 cities across 192 countries, this paper examines the main economic and financial drivers of change to regional urban water and wastewater tariffs from 2018 to 2019. Historically, the average global price for water and wastewater services increased from US$ 1.70/m3 in 2011 to US$ 2.16/m3 in 2019, equating to an annual rise in the mean global combined water tariff of ∼3.4%. The analysis indicates that for the studied regions, the financial and economic costs associated with recurring droughts, old infrastructure, subsidy cuts, increasing energy costs and a shift to alternative water resources such as desalination all contribute to changes in tariffs. Further research on the social and political drivers of change in tariffs is needed, in order to provide a holistic understanding of the balance required to be struck between the objectives of affordability and cost-recovery for achieving global access to water and sanitation.

Background: Substantial increases in plastic production have resulted in plastics proliferating of in the environment, with subsequent seabed plastic deposition and ingestion by marine fauna. There is an urgent need to monitor mismanaged plastic waste from household consumption. Household expenditure survey analysis has quantified mismanaged plastic waste generated from household packaged (bottled or bagged) water consumption, but not from consumption of other products. Methods: To evaluate whether household expenditure surveys can quantify mismanaged waste from other widely consumed commodities, we quantify mismanaged plastic waste from the domestic consumption of cooking oil alongside packaged water in urban Greater Accra, Ghana, and all cities nationally in Kenya using two household expenditure surveys. Results: Household survey-derived estimates indicate packaged water consumption generates considerably more plastic waste than oil packaging in Greater Accra, whereas oil packaging generates more plastic waste than packaged water in urban Kenya. Conclusion: By successfully transferring a survey analysis protocol from packaged water to cooking oil, we conclude that there is ample potential for expenditure surveys to be used internationally to quantify mismanaged plastic waste from households. However, uncertainties affecting mismanaged waste estimates need to be accounted for.

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