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Glaciers are a critical freshwater resource of river recharge in arid areas around the world. In recent decades, glaciers have shown evidence of retreat due to climate change, and the accelerated ablation of glaciers and associated impacts on water resources have received widespread attention. Glacier variations result from climate change, so they can serve as an indicator of climate change. Considering the climatic differences in different elevation ranges, it is worthwhile to explore whether different responses exist between glacier area and air temperature in each elevation zone. In this study, we selected a typical arid inland river basin (Sugan Lake Basin) in the western Qilian Mountains of Northwest China to analyze the glacier variations and their response to climate change. The glacier area data from 1989 to 2016 were delineated using Landsat Thematic Mapper (TM), Enhanced TM+ (ETM+) and Operational Land Imager (OLI) images. We compared the relationships between glacier area and air temperature at seven meteorological stations in the glacier-covered areas and in the Sugan Lake Basin, and further analyzed the relationship between glacier area and mean air temperature of the glacier surfaces in July–August in the elevation range of 4700–5500 m a.s.l. by the linear regression method and correlation analysis. In addition, based on the linear regression relationship established between glacier area and air temperature in each elevation zone, we predicted glacier areas under future climate scenarios during the periods of 2046–2065 and 2081−2100. The results indicate that the glaciers experienced a remarkable shrinkage from 1989 to 2016 with a shrinkage rate of −1.61 km2/a (−0.5%/a), and the rising temperature is the decisive factor dominating glacial retreat; there is a significant negative linear correlation between glacier area and mean air temperature of the glacier surfaces in July–August in each elevation zone from 1989 to 2016. The variations in glaciers are far less sensitive to changes in precipitation than to changes in air temperature. Due to the influence of climate and topographic conditions, the distribution of glacier area and the rate of glacier ablation first increased and then decreased in different elevation zones. The trend in glacier shrinkage will continue because air temperature will continue to increase in the future, and the result of glacier retreat in each elevation zone will be slightly slower than that in the entire study area. Quantitative glacier research can more accurately reflect the response of glacier variations to climate change, and the regression relationship can be used to predict the areas of glaciers under future climate scenarios. These conclusions can offer effective references for assessing glacier variations and their response to climate change in arid inland river basins in Northwest China as well as other similar regions in the world.

The particle filter‐based data assimilation method is an effective tool to adjust model states based on observations. In this study, we proposed a modified particle filter‐based data assimilation method with a local weighting procedure (MPFDA‐LW) for a high‐precision two‐dimensional hydrodynamic model (HydroM2D) in dam‐break flood simulation. Moreover, a particle filter‐based data assimilation method with a global weighting procedure (PFDA‐GW) for the HydroM2D model was also investigated. The MPFDA‐LW and the PFDA‐GW for the HydroM2D model, respectively, adopted spatially nonuniform and uniform Manning's roughness coefficients. The MPFDA‐LW considering spatial‐temporal variability of Manning's roughness coefficient could significantly improve the performances of the HydroM2D model in simulating water stages at all gauges simultaneously, whereas the PFDA‐GW considering temporal variability of Manning's roughness coefficient could only slightly improve the performances of the HydroM2D model in simulating water stages at a few gauges. The MPFDA‐LW is more suitable for improving the performance of 2‐D hydrodynamic models in flood inundation simulation than the PFDA‐GW. We proposed a data assimilation framework for a high‐precision 2‐D hydrodynamic model (HydroM2D) based on a modified PF methodThe PF‐based data assimilation (PFDA) method for the HydroM2D model considered the spatial‐temporal variability of Manning's roughness coefficientThe PF‐based data assimilation could simultaneously improve the performances of the HydroM2D in simulating water stages at all gauges

Abstract: The distant downstream proportional integral (PI) feedback control was applied to the W-M lateral canal of the Maricopa Stanfield Irrigation and Drainage District located in central Arizona, U.S.A. Proper configuration of those controls for the canal can be challenging. Towards this end, an integrated approach to the design of an automatic control system for the canal was proposed. This approach presented herein is not only a systematical review of previous work, but also represents a further advance of the previous simulation study by Tsinghua University (Shang et al, 2011) on relating the canal control algorithm to local PI controls for the real canal. To evaluate the control system potential, performance of the control algorithm that was obtained through implanting predicative module into linear quadratic regulator (LQR) was analyzed with singular value bode. Additional “manufactured” tests were conducted to compare with the control system that is currently in use. The results indicated that the developed control system rather than the system in current use had considerable potential to closely match discharge at the downstream check structures with those ordered by water users while maintaining the water level throughout the length of the canal.

Abstract: The particular challenges of modeling control systems for the middle route of the south-to-north water transfer project are illustrated. Open channel dynamics are approximated by well-known Saint-Venant nonlinear partial differential equations. For better control purpose, the finite difference method is used to discretize the Saint-Venant equations to form the state space model of channel system. To avoid calculation divergence and improve control stability, balanced model reduction together with poles placement procedure is proposed to develop the control scheme. The entire process to obtain this scheme is described in this paper, important application issue is considered as well. Experimental results show the adopted techniques are properly used in the control scheme design, and the system is able to drive the discharge to the demanded set point or maintain it around a reasonable range even if comes across big withdrawals.

Abstract: The unsteady flow in the Middle Route South-to-North Water Transfer Channel was simulated numerically using an implicit solution procedure for the Saint Venant equations. An equivalent roughness was used to simulate the effect of many transfer structures on the water levels in the main channel. Various gate operating and control methods were analyzed to study the response to disturbances produced by varying the flow rates through the Tianjin outlet. The results show that when the inflow at the head changes in the same way as the sum of the flow rates through all the outlets, the transition time and the fluctuation of the water levels using the timed gate operation method are less than when using the simultaneous gate operation method, but the variations of the gate openings and flow rates through each control gate are much larger. The flow disturbances produced by the Tianjin outlet can be rectified within several channel sections and the transition time can be greatly shortened by allowing the water levels immediately upstream of the control gates to vary within proscribed ranges, rather than being held constant. [Copyright &y& Elsevier]

Abstract: The distributed system with high performance and stability is commonly adopted in large scale scientific and engineering computing. In this paper, we discuss a fault-tolerant mechanism under Linux circumstance to improve the fault-tolerant ability of the system, namely a scheme and frame to form the stable computing platform. In terms of the structure and function of the distributed system, active list and file invocation strategies are employed in the task management. System multilevel fault-tolerance can be achieved by repeated processes in a single node and task migration on multi-nodes. Manager node agent introduced in this paper administrates the nodes using the list, disposes of the tasks according to the nodes'' performance, and hence, to be able to make full use of the cluster resources. An evaluation method is proposed to appraise the performance. The analyzed results show the usefulness of the scheme proposed except for some additional overhead of memory consumption. [Copyright &y& Elsevier]

Abstract: This paper describes a parallel computing platform using the existing facilities for the digital watershed model. In this paper, distributed multi-layered structure is applied to the computer cluster system, and the MPI-2 is adopted as a mature parallel programming standard. An agent is introduced which makes it possible to be multi-level fault-tolerant in software development. The communication protocol based on checkpointing and rollback recovery mechanism can realize the transaction reprocessing. Compared with conventional platform, the new system is able to make better use of the computing resource. Experimental results show the speedup ratio of the platform is almost 4 times as that of the conventional one, which dem-onstrates the high efficiency and good performance of the new approach. [Copyright &y& Elsevier]