It could be argued that nowhere has the impact of dams on rivers been more important than in China, where since 1950 almost half of the world's large dams (higher than 15 meters) have been built ]Fuggle and Smith, 2000]. China's Yangtze River (Changjiang)—the largest river in south Asia (1.8 million square kilometers) and whose basin is home to more than 400 million inhabitants—alone has more than 50,000 dams within its watershed, including the world's largest, the Three Gorges Dam (TGD) (Figure 1a ). Water and sediment began being impounded behind the TGD in June 2003, and two years after impoundment, river sediment discharge downstream (at Datong Station) had decreased by nearly half of its 2002 load (Figure 1c). However, the decrease in Yangtze sediment load did not begin with TGD impoundment. Rather, the sediment load at Datong has declined continually since 1987 despite a slight increase in river discharge (Figure 1c ). The change in pre‐TGD loads atYichang, just downstream from the TGD, has been even more extreme, decreasing by approximately 300 million tons in 1986–2002, before declining another 130 million tons after 2002 (Figure 1b). All of this suggests that collective changes on the Yangtze upstream (above Yichang) have been more important in decreasing the river's sediment load than the TGD.

a b s t r a c tA large volume of fracturing fluid is pumped into a well to stimulate shale formation. The water is imbibed into the reservoir during this procedure. The effect of the imbibed water on gas recovery is still in debate. In this work, we study the spontaneous imbibition of water into marine shale samples from the Sichuan Basin and continental shale samples from Erdos Basin to explore the fluid imbibition characteristics and permeability change during water imbibition.Comparison of imbibition experiments shows that shale has stronger water imbibition and diffusion capacity than relatively higher permeability sandstone. Once the imbibition stops, water in shale has stronger ability to diffuse into deeper matrix, the water content in the main flow path decreases.Experiments in this study show that marine shale has stronger water imbibition capacity than continental shale. The permeability of continental shale decreases significantly with increasing imbibition water volume; however, the permeability of marine shale decreases at first and increases after a certain imbibition time. The induced fracture is obvious in the marine shale. SEM analysis shows that the relationship between the clay mineral and organic matter of continental shale is much more complex than that of marine shale, which may be the key factor restricting the water imbibition because the flow path is trapped by swelled clay minerals.Through this study, we concluded that whether gas recovery benefits from water imbibition depends on three aspects: 1) the diffusion ability of liquid into matrix; 2) the new cracks introduced by imbibed water; and 3) the formation sensibility. This study is useful for optimizing fracture fluids and determining the best flow-back method.

A strategy that informs on countries' potential losses due to lack of climate action may facilitate global climate governance. Here, we quantify a distribution of mitigation effort whereby each country is economically better off than under current climate pledges. This effort-sharing optimizing approach applied to a 1.5°C and 2°C global warming threshold suggests self-preservation emissions trajectories to inform NDCs enhancement and longterm strategies. Results show that following the current emissions reduction efforts, the whole world would experience a washout of benefit, amounting to almost 126.68-616.12 trillion dollars until 2100 compared to 1.5°C or well below 2°C commensurate action. If countries are even unable to implement their current NDCs, the whole world would lose more benefit, almost 149.78-791.98 trillion dollars until 2100. On the contrary, all countries will be able to have a significant positive cumulative net income before 2100 if they follow the selfpreservation strategy.

Policies under consideration within the Climate Convention would impose CO2 controls on only a subset of nations. A model of economic growth and emissions, coupled to an analysis of the climate system, is used to explore the consequences of a sample proposal of this type. The results show how economic burdens are likely to be distributed among nations, how carbon "leakage" may counteract the reductions attained, and how policy costs may be influenced by emissions trading. We explore the sensitivity of results to uncertainty in key underlying assumptions, including the influence on economic impacts and on the policy contribution to long-term climate goals.

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More and more complex scientific workflows are now executed on computational grids. In addition to the challenges of managing and scheduling these workflows, additional reliability challenges arise because of the unreliable nature of large-scale grid infrastructure. Fault tolerance mechanisms like over-provisioning and checkpoint-recovery are used in current grid application management systems to address these reliability challenges. In this work, we propose new approaches that combine these fault tolerance techniques with existing workflow scheduling algorithms. We present a study on the effectiveness of the combined approaches by analyzing their impact on the reliability of workflow execution, workflow performance and resource usage under different reliability models, failure prediction accuracies and workflow application types.