Julie Padowski

Global analysis of urban surface water supply vulnerability

This study presents a global analysis of urban water supply vulnerability in 71 surface-water supplied cities, with populations exceeding 750 000 and lacking source water diversity. Vulnerability represents the failure of an urban supply-basin to simultaneously meet demands from human, environmental and agricultural users. We assess a baseline (2010) condition and a future scenario (2040) that considers increased demand from urban population growth and projected agricultural demand. We do not account for climate change, which can potentially exacerbate or reduce urban supply vulnerability. In 2010, 35% of large cities are vulnerable as they compete with agricultural users. By 2040, without additional measures 45% of cities are vulnerable due to increased agricultural and urban demands. Of the vulnerable cities in 2040, the majority are river-supplied with mean flows so low (1200 liters per person per day, l/p/d) that the cities experience ‘chronic water scarcity’ (1370 l/p/d). Reservoirs supply the majority of cities facing individual future threats, revealing that constructed storage potentially provides tenuous water security. In 2040, of the 32 vulnerable cities, 14 would reduce their vulnerability via reallocating water by reducing environmental flows, and 16 would similarly benefit by transferring water from irrigated agriculture. Approximately half remain vulnerable under either potential remedy.

Assessment of human–natural system characteristics influencing global freshwater supply vulnerability

Global freshwater vulnerability is a product of environmental and human dimensions, however, it is rarely assessed as such. Our approach identifies freshwater vulnerability using four broad categories: endowment, demand, infrastructure, and institutions, to capture impacts on natural and managed water systems within the coupled human–hydrologic environment. These categories are represented by 19 different endogenous and exogenous characteristics affecting water supply vulnerability. By evaluating 119 lower per capita income countries (<

Estimating watershed degradation over the last century and its impact on water-treatment costs for the world's large cities.

10 725), we find that every nation experiences some form of vulnerability. Institutional vulnerability is experienced most commonly, occurring in 44 nations, and 23 countries suffer deficiencies in all four categories. Of these highly vulnerable countries, Jordan is the most vulnerable, reporting the greatest number of characteristics (5 of 19) at critical vulnerability levels, with Yemen and Djibouti nearly as vulnerable. Surprising similarities in vulnerability were also found among geographically disparate nations such as Vietnam, Sri Lanka, and Guatemala. Determining shared patterns of freshwater vulnerability provides insights into why water supply vulnerabilities are manifested in human–water systems at the national scale.

Corrigendum: Global analysis of urban surface water supply vulnerability (2014 Environ. Res. Lett. 9 104004)

Significance Urban water-treatment costs depend on the water quality at the city’s source, which in turn depends on the land use in the source watersheds. Here, we show that globally urban source watershed degradation is widespread, with 9 in 10 cities losing significant amounts of natural land cover in their source watersheds to agriculture and development. This watershed degradation has impacted the cost of water treatment for about one in three large cities globally, increasing those costs by about half. This increase in cost matters because increases in water-treatment costs are paid for by those living in cities, so watershed degradation has had a real quantitative cost to hundreds of millions of urbanites. Urban water systems are impacted by land use within their source watersheds, as it affects raw water quality and thus the costs of water treatment. However, global estimates of the effect of land cover change on urban water-treatment costs have been hampered by a lack of global information on urban source watersheds. Here, we use a unique map of the urban source watersheds for 309 large cities (population > 750,000), combined with long-term data on anthropogenic land-use change in their source watersheds and data on water-treatment costs. We show that anthropogenic activity is highly correlated with sediment and nutrient pollution levels, which is in turn highly correlated with treatment costs. Over our study period (1900–2005), median population density has increased by a factor of 5.4 in urban source watersheds, whereas ranching and cropland use have increased by a factor of 3.4 and 2.0, respectively. Nearly all (90%) of urban source watersheds have had some level of watershed degradation, with the average pollutant yield of urban source watersheds increasing by 40% for sediment, 47% for phosphorus, and 119% for nitrogen. We estimate the degradation of watersheds over our study period has impacted treatment costs for 29% of cities globally, with operation and maintenance costs for impacted cities increasing on average by 53 ± 5% and replacement capital costs increasing by 44 ± 14%. We discuss why this widespread degradation might be occurring, and strategies cities have used to slow natural land cover loss.

Effect of Passive Surface Water Flux Meter Design on Water and Solute Mass Flux Estimates

Salem, Oregon was inadvertently included in the analysis, but it does not meet the study threshold population of 750 000 people. This reduces the number of cities in this study from 71 to 70. Changes to figure 1, and tables 1, 2 and 3 as well as the text are shown below. The changes do not affect the overall results or conclusions.

Incorporating Social System Dynamics in the Columbia River Basin: Food-Energy-Water Resilience and Sustainability Modeling in the Yakima River Basin

Standard methods for determining pollutant loads in streams typically require the collection of separate instantaneous measurements of water velocities and solute concentrations at discrete points in space and time. A recently developed device, the passive surface water flux meter (PSFM), has been introduced as an alternate method for the measurement of time-integrated surface water flux (velocity) and solute mass flux. This paper extends PSFM development by evaluating and comparing two PSFM designs in laboratory flumes, as well as reporting on initial steady-state field testing. The shape of the PSFM body determines the velocity with which water passes through the device, and different designs may thus be preferred for different applications. Experiments compared the accuracy of flux measurement by the previously introduced hydrofoil-shaped PSFM and nitrate-sorbing cartridge with that of a newly designed cylindrical-shaped PSFM and phosphate-sorbing cartridges. Testing was performed in a laboratory flume...

Water on an urban planet: Urbanization and the reach of urban water infrastructure

In the face of climate change, achieving resilience of desirable aspects of food-energy-water (FEW) systems already strained by competing multi-scalar social objectives requires interdisciplinary approaches. This study is part of a larger effort exploring “Innovations in the Food-Energy-Water Nexus (INFEWS)” in the Columbia River Basin (CRB) through coordinated modeling and simulated management scenarios. Here, we focus on a case study and conceptual mapping of the Yakima River Basin (YRB), a sub-basin of the CRB. Previous research on FEW system management and resilience includes some attention to social dynamics (e.g., economic and governance systems); however, more attention to social drivers and outcomes is needed. Our goals are to identify several underutilized ways to incorporate social science perspectives into FEW nexus research and to explore how this interdisciplinary endeavor alters how we assess innovations and resilience in FEW systems. First, we investigate insights on FEW nexus resilience from the social sciences. Next, we delineate strategies for further incorporation of social considerations into FEW nexus research, including the use of social science perspectives and frameworks such as socio-ecological resilience and community capitals. Then, we examine a case study of the YRB, focusing on the historical development of the FEW nexus and innovations. We find that a resilience focus applied to the FEW nexus can inadvertently emphasize a status quo imposed by those already in power. Incorporating perspectives from the social sciences, which highlight issues related to inequality, power, and social justice, can address these shortcomings and inform future innovations. Finally, we use causal loop diagrams to explore the role of the social in the FEW nexus, and we suggest ways to incorporate social aspects into an existing stock and flow object-oriented modeling system. This project represents a starting point for a continued research agenda that incorporates social dynamics into FEW system resilience modeling and management in the CRB.