Stewart, R.J., W.M. Wollheim, A. Miara, C.J. Vörösmarty, B. Fekete, R.B. Lammers, and B. Rosenzweig, 2013: “Horizontal cooling towers: riverine ecosystem services and the fate of thermoelectric heat in the contemporary Northeast US.” Environmental Research Letters, v. 8, paper no. 025010, doi: 10.1088/1748-9326/8/2/025010.
The electricity sector is dependent on rivers to provide ecosystem services that help regulate excess heat, either through provision of water for evaporative cooling or by conveying, diluting and attenuating waste heat inputs. Reliance on these ecosystem services alters flow and temperature regimes, which impact fish habitat and other aquatic ecosystem services. We demonstrate the contemporary (2000–2010) dependence of the electricity sector on riverine ecosystem services and associated aquatic impacts in the Northeast US, a region with a high density of thermoelectric power plants. We quantify these dynamics using a spatially distributed hydrology and water temperature model (the framework for aquatic modeling in the Earth system), coupled with the thermoelectric power and thermal pollution model. We find that 28.4% of thermoelectric heat production is transferred to rivers, whereas 25.9% is directed to vertical cooling towers. Regionally, only 11.3% of heat transferred to rivers is dissipated to the atmosphere and the rest is delivered to coasts, in part due to the distribution of power plants within the river system. Impacts to the flow regime are minimal, while impacts to the thermal regime include increased river lengths of unsuitable habitats for fish with maximum thermal tolerances of 24.0, 29.0, and 34.0 ° C in segments downstream of plants by 0.6%, 9.8%, and 53.9%, respectively. Our analysis highlights the interactions among electricity production, cooling technologies, aquatic impacts, and ecosystem services, and can be used to assess the full costs and tradeoffs of electricity production at regional scales.
A video abstract is also available at the link above.
Open Access
Meldrum, J., S. Nettles-Anderson, G. Heath, and J. Macknick, 2013: “Life cycle water use for electricity generation: a review and harmonization of literature estimates.” Environmental Research Letters, v. 8, paper no. 015031, doi: 10.1088/1748-9326/8/1/015031.
This article provides consolidated estimates of water withdrawal and water consumption for the full life cycle of selected electricity generating technologies, which includes component manufacturing, fuel acquisition, processing, and transport, and power plant operation and decommissioning. Estimates were gathered through a broad search of publicly available sources, screened for quality and relevance, and harmonized for methodological differences. Published estimates vary substantially, due in part to differences in production pathways, in defined boundaries, and in performance parameters. Despite limitations to available data, we find that: water used for cooling of thermoelectric power plants dominates the life cycle water use in most cases; the coal, natural gas, and nuclear fuel cycles require substantial water per megawatt-hour in most cases; and, a substantial proportion of life cycle water use per megawatt-hour is required for the manufacturing and construction of concentrating solar, geothermal, photovoltaic, and wind power facilities. On the basis of the best available evidence for the evaluated technologies, total life cycle water use appears lowest for electricity generated by photovoltaics and wind, and highest for thermoelectric generation technologies. This report provides the foundation for conducting water use impact assessments of the power sector while also identifying gaps in data that could guide future research.
Open Access
Pederson, G.T., J.L. Betancourt, and G.J. McCabe, 2013: “Regional patterns and proximal causes of the recent snowpack decline in the Rocky Mountains, U.S.” Geophysical Research Letters, v. 40, doi: 10.1002/grl.50424.
We used a first-order, monthly snow model and observations to disentangle seasonal influences on 20th century,regional snowpack anomalies in the Rocky Mountains of western North America, where interannual variations in cool-season (November–March) temperatures are broadly synchronous, but precipitation is typically antiphased north to south and uncorrelated with temperature. Over the previous eight centuries, regional snowpack variability exhibits strong, decadally persistent north-south (N-S) antiphasing of snowpack anomalies. Contrary to the normal regional antiphasing, two intervals of spatially synchronized snow deficits were identified. Snow deficits shown during the 1930s were synchronized north-south by low cool-season precipitation, with spring warming (February–March) since the 1980s driving the majority of the recent synchronous snow declines, especially across the low to middle elevations. Spring warming strongly influenced low snowpacks in the north after 1958, but not in the south until after 1980. The post-1980, synchronous snow decline reduced snow cover at low to middle elevations by ~20% and partly explains earlier and reduced streamflow and both longer and more active fire seasons. Climatologies of Rocky Mountain snowpack are shown to be seasonally and regionally complex, with Pacific decadal variability positively reinforcing the anthropogenic warming trend.
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Hagemann, S., C. Chen, D.B. Clark, S. Folwell, S.N. Gosling, I. Haddeland, N. Hanasaki, J. Heinke, F. Ludwig, F. Voss, and A.J. Wiltshire, 2013: “Climate change impact on available water resources obtained using multiple global climate and hydrology models.” Earth System Dynamics, v. 4, pp. 129-144, doi: 10.5194/esd-4-129-2013.
Climate change is expected to alter the hydrological cycle resulting in large-scale impacts on water availability. However, future climate change impact assessments are highly uncertain. For the first time, multiple global climate (three) and hydrological models (eight) were used to systematically assess the hydrological response to climate change and project the future state of global water resources. This multi-model ensemble allows us to investigate how the hydrology models contribute to the uncertainty in projected hydrological changes compared to the climate models. Due to their systematic biases, GCM outputs cannot be used directly in hydrological impact studies, so a statistical bias correction has been applied. The results show a large spread in projected changes in water resources within the climate–hydrology modelling chain for some regions. They clearly demonstrate that climate models are not the only source of uncertainty for hydrological change, and that the spread resulting from the choice of the hydrology model is larger than the spread originating from the climate models over many areas. But there are also areas showing a robust change signal, such as at high latitudes and in some midlatitude regions, where the models agree on the sign of projected hydrological changes, indicative of higher confidence in this ensemble mean signal. In many catchments an increase of available water resources is expected but there are some severe decreases in Central and Southern Europe, the Middle East, the Mississippi River basin, southern Africa, southern China and south-eastern Australia.
Open Access
Jasechko, S., Z.D. Sharp, J.J. Gibson, S.J. Birks, Y. Yi, and P.J. Fawcett, 2013: “Terrestrial water fluxes dominated by transpiration.” Nature, v. 496, pp. 347-350, doi: 10.1038/nature11983.
Renewable fresh water over continents has input from precipitation and losses to the atmosphere through evaporation and transpiration. Global-scale estimates of transpiration from climate models are poorly constrained owing to large uncertainties in stomatal conductance and the lack of catchment-scale measurements required for model calibration, resulting in a range of predictions spanning 20 to 65 per cent of total terrestrial evapotranspiration (14,000 to 41,000 km3 per year). Here we use the distinct isotope effects of transpiration and evaporation to show that transpiration is by far the largest water flux from Earth’s continents, representing 80 to 90 per cent of terrestrial evapotranspiration. On the basis of our analysis of a global data set of large lakes and rivers, we conclude that transpiration recycles 62,000 ± 8,000 km3 of water per year to the atmosphere, using half of all solar energy absorbed by land surfaces in the process. We also calculate CO2 uptake by terrestrial vegetation by connecting transpiration losses to carbon assimilation using water-use efficiency ratios of plants, and show the global gross primary productivity to be 129 ± 32 gigatonnes of carbon per year, which agrees, within the uncertainty, with previous estimates. The dominance of transpiration water fluxes in continental evapotranspiration suggests that, from the point of view of water resource forecasting, climate model development should prioritize improvements in simulations of biological fluxes rather than physical (evaporation) fluxes.
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Jarvis, W.T., 2013: “Water scarcity: Moving beyond indexes to innovative institutions.” Ground Water, doi: 10.1111/gwat.12059.
Water scarcity is a media darling often times described as a trigger of conflict in arid regions, a by-product of human influences ranging from desertification to climate change, or a combination of natural- and human-induced changes in the water cycle. A multitude of indexes have been developed over the past 20 years to define water scarcity to map the “problem” and guide international donor investment. Few indexes include groundwater within the metrics of “scarcity.” Institutional communication contributes to the recognition of local or regional water scarcity. However, evaluations that neglect groundwater resources may incorrectly define conditions as scarce. In cases where there is a perception of scarcity, the incorporation of groundwater and related storage in aquifers, political willpower, new policy tools, and niche diplomacy often results in a revised status, either reducing or even eliminating the moniker locally. Imaginative conceptualization and innovative uses of aquifers are increasingly used to overcome water scarcity.
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Jasechko,S., Z.D. Sharp, J.J. Gibson, S.J. Birks, Y. Yi, and P.J. Fawcett, 2013: “Terrestrial water fluxes dominated by transpiration.” Nature, v. 496, pp. 347-350, doi: 10.1038/nature11983.
Renewable fresh water over continents has input from precipitation and losses to the atmosphere through evaporation and transpiration. Global-scale estimates of transpiration from climate models are poorly constrained owing to large uncertainties in stomatal conductance and the lack of catchment-scale measurements required for model calibration, resulting in a range of predictions spanning 20 to 65 per cent of total terrestrial evapotranspiration (14,000 to 41,000 km3 per year). Here we use the distinct isotope effects of transpiration and evaporation to show that transpiration is by far the largest water flux from Earth’s continents, representing 80 to 90 per cent of terrestrial evapotranspiration. On the basis of our analysis of a global data set of large lakes and rivers, we conclude that transpiration recycles 62,000 ± 8,000 km3 of water per year to the atmosphere, using half of all solar energy absorbed by land surfaces in the process. We also calculate CO2 uptake by terrestrial vegetation by connecting transpiration losses to carbon assimilation using water-use efficiency ratios of plants, and show the global gross primary productivity to be 129 ± 32 gigatonnes of carbon per year, which agrees, within the uncertainty, with previous estimates. The dominance of transpiration water fluxes in continental evapotranspiration suggests that, from the point of view of water resource forecasting, climate model development should prioritize improvements in simulations of biological fluxes rather than physical (evaporation) fluxes.
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Busby, J.W., T.G. Smith, K.L. White, and S.M. Strange, 2013: “Climate change and insecurity: Mapping vulnerability in Africa.” International Security, v. 37, pp. 132-172, doi: 10.1162/ISEC_a_00116.
Many experts argue that climate change will exacerbate the severity and number of extreme weather events. Such climate-related hazards will be important security concerns and sources of vulnerability in the future regardless of whether they contribute to conflict. This will be particularly true where these hazards put large numbers of people at risk of death, requiring the diversion of either domestic or foreign military assets to provide humanitarian relief. Vulnerability to extreme weather, however, is only partially a function of physical exposure. Poor, marginalized communities that lack access to infrastructure and services, that have minimal education and poor health care, and that exist in countries with poor governance are likely to be among the most vulnerable. Given its dependence on rainfed agriculture and its low adaptive capacity, Africa is thought to be among the most vulnerable continents to climate change. That vulnerability, however, is not uniformly distributed. Indicators of vulnerability within Africa include the historic incidence of climate-related hazards, population density, household and community resilience, and governance and political violence. Among the places in Africa most vulnerable to the security consequences of climate change are parts of the Democratic Republic of the Congo, Guinea, Sierra Leone, Somalia, and South Sudan.
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Brown, T.C., R. Foti, and J.A. Ramirez, 2013: “Projected freshwater withdrawals in the United States under a changing climate.” Water Resources Research, v. 49, doi: 10.1002/wrcr.20076.
Relying on the U.S. Geological Survey water use data for the period 1960−2005, this paper summarizes past water use and then projects future water use based on the trends in water use efficiency and major drivers of water use. Water use efficiency has improved in most sectors. Over the past 45 years, withdrawals in industry and at thermoelectric plants have steadily dropped per unit of output. In addition, domestic and public withdrawals per capita, and irrigation withdrawals per unit area in most regions of the west, have recently begun to decrease. If these efficiency trends continue and trends in water use drivers proceed as expected, in the absence of additional climate change the desired withdrawals in the United States over the next 50 years are projected to stay within 3% of the 2005 level despite an expected 51% increase in population. However, including the effects of future climate change substantially increases this projection. The climate-based increase in the projected water use is attributable mainly to increases in agricultural and landscape irrigation in response to rising potential evapotranspiration, and to a much lesser extent to water use in electricity production in response to increased space cooling needs as temperatures rise. The increases in projected withdrawal vary greatly across the 98 basins examined, with some showing decreases and others showing very large increases, and are sensitive to the emission scenario and global climate model employed. The increases were also found to be larger if potential evapotranspiration is estimated using a temperature-based method as opposed to a physically based method accounting for energy, humidity, and wind speed.
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Meybeck, M., M. Kummu, and H.H. Dürr, 2013: “Global hydrobelts and hydroregions: improved reporting scale for water-related issues?” Hydrology and Earth System Science, v. 17, pp. 1093-1111, doi: 10.5194/hess-17-1093-2013.
Global-scale water issues such as its availability, water needs or stress, or management, are mapped at various resolutions and reported at many scales, mostly along political or continental boundaries. As such, they ignore the fundamental heterogeneity of hydroclimates and natural boundaries of river basins. Here we describe the continental landmasses at two levels: eight hydrobelts strictly limited by river basins, defined at a 30’ (0.5°) resolution, which are decomposed on continents as 26 hydroregions. The belts were defined and delineated, based primarily on the annual average temperature (T) and run-off (q), to maximise inter-belt differences and minimise intra-belt variability.
This new global puzzle defines homogeneous and near-contiguous entities with similar hydrological and thermal regimes, glacial and postglacial basin histories, endorheism distribution and sensitivity to climate variations. The mid-latitude, dry and subtropical belts have northern and southern analogues and a general symmetry can be observed for T and q between them. The boreal and equatorial belts are unique. Population density between belts and between the continents varies greatly, resulting in pronounced differences between the belts with analogues in both hemispheres.
Hydroregions (median size 4.7 M km2) are highly contrasted, with the average q ranging between 6 and 1393 mm yr−1 and the average T between −9.7 and +26.3 °C, and a population density ranging from 0.7 to 0.8 p km−2 for the North American boreal region and some Australian hydroregions to 280 p km−2 for some Asian hydroregions. The population/run-off ratio, normalised to a reference pristine region, is used to map and quantify the global population at risk of severe water quality degradation. Our initial tests suggest that hydrobelt and hydroregion divisions are often more appropriate than conventional continental or political divisions for the global analysis of river basins within the Earth system and of water resources.
Open Access
