Effects of drawdown scenario on retrogressive lateral erosion in a reservoir

The drawdown of reservoirs behind dams is an important management strategy (e.g., for removal of aging infrastructure, flushing of sediment), and an opportunity to study erosional processes. A numerical model was developed to examine retrogressive bank erosion across reservoir drawdown scenarios and to evaluate factors controlling the rate, volume, and mechanisms of lateral erosion. Modeled processes included dynamic drawdown of groundwater, sequential slope failures via limit equilibrium analysis, and retrogression considering stress interaction between failing blocks. Field measurements were coupled with Staged, Slow, and Rapid drawdown scenarios. Results highlight the importance of including retrogression as an avenue for lateral erosion, as sequential block failures were found to occur in all scenarios except Slow drawdown. This result indicates that bank stability models without some means of characterizing the evolution of slope failure during drawdown are likely underestimating bank failure rates and volumes. In contrast, dynamic groundwater was not found to be a dominant control for any drawdown scenario. Model results also demonstrate that the drawdown increment is a first-order control on slope instability via the development of drained or undrained conditions. A majority of failures occurred under undrained conditions. To maximize slope stability, using slow drawdown to activate internal friction under drained conditions is essential. The design of the drawdown rate created a tradeoff between the amount of impact created and when the impact is produced. The study also articulated the need for coupling models and field observations for rapidly changing systems.     

Comparison of Machine Learning Models Performance on Simulating Reservoir Outflow: A Case Study of Two Reservoirs in Illinois,U.S.A.

Reservoir outflow is an important variable for understanding hydrological processes and water resource management. Natural streamflow variation, in addition to the streamflow regulation provided by dams and reservoirs, can make streamflow difficult to understand and predict. This makes them a challenge to accurately simulate hydrologic processes at a daily scale. In this study, three Machine Learning (ML) algorithms, Random Forest (RF), Support Vector Machine (SVM), and Artificial Neural Network (ANN), were examined and compared to model reservoir outflow. Past, current, and future hydrologic and meteorological data were used as model inputs, and the outflow of next day was used as prediction. Simulation results demonstrated that all three models can reasonably simulate reservoir outflow. For Carlyle Lake, the coefficient of determination and Nash–Sutcliffe efficiency were each close to one for the three models. The coefficient of determination, relative mean bias, and root mean square error indicated that the SVM performed better than the RF and ANN, but the SVM output displayed a larger relative mean bias than that from RF and ANN. For Lake Shelbyville, the ANN model performed better than RF and SVM when considering the coefficient of determination, Nash–Sutcliffe efficiency, relative mean bias, and root mean square error. The study results demonstrate that the three ML algorithms (RF, SVM, and ANN) are all promising tools for simulating reservoir outflow. Both the accuracy and efficacy of the three ML algorithms are considered to support practitioners in planning reservoir management.     

Status and circulation characteristics of soil water in dryland field of southeast Shanxi Province

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尾矿库地震液化机理及抗震评估指标体系研究

2008年"5.12"汶川大地震中,四川、陕西和甘肃三省尾矿库均受到不同程度的破坏和影响。本文针对四川汶川地震造成灾区尾矿库排洪系统失效,坝基沉降,坝体滑坡、垮塌、开裂等现状,对尾矿库地震溃坝机理进行了分析,研究了地震作用机理和地震液化的影响因素;在此基础上,建立起用于评估尾矿库抗震能力和地震溃坝可能性的指标体系,指标体系考虑了地震强度、防洪、抗滑、抗渗透和安全管理五个方面,能够较为全面的分析和评估尾矿库在抗震方面的基本特性,并通过研究给出了各个指标的分级方法。该体系的建立为尾矿库抗震能力评估、避免特殊工况下尾矿库溃坝事故的发生具有一定应用价值,可为尾矿库运行期的安全管理提供依据。     

Water quantity and quality dynamics of the THC — Tuyamuyun Hydroengineering Complex — And implications for reservoir operation

Background In the Aral Sea basin, safe water resources are scarce and steadily becoming scarcer. Particularly high quality water is going to become a rare good. The object of the study was the Tuyamuyun Hydroengineering Complex (THC), a complex of artificial water reservoirs located in the lower Amu Darya River, which provides water for irrigation, industry, and drinking for the lower Amu Darya region. The focus was on operation of one of its four reservoirs, the Kaparas, which is mainly used for drinking water supply. The objective includes the investigation of impacts of conventional operation schemes on the reservoir water quality for improving drinking water quality (salinity). Basic operation rules for Kaparas, which can be considered as representative for conventional dam operation under dry year conditions, had to be identified and improved operation schemes derived. Methods Existing data archives were analysed, and further data were acquired from field surveys, data processing and modelling studies. Historical data were identified, which are appropriate to determine representative schemes for the conventional operation. For the simulation of time-dependent and depth-dependent changes of reservoir salinisation, the reservoir water quality model Lac was used and linked with the THC model. Results and Discussion Modelling results for the simulation of temperature dynamics and density stratification showed a sufficient congruence with the measured temperature profiles. The conformity of measured and calculated salt concentration is basically ensured. The reservoir, which fill with higher saline water at the end of the summer, aggravates the entrainment of high saline water in the entire water column. Conclusions The current conventional operation regime mainly leads to filling the Kaparas reservoir with high saline water during the winter months. Even in the event of starting with comparable low salinity levels, the simulation demonstrates the rapid deterioration of the reservoir water quality. Under dry year conditions, the WHO standards for drinking water will be exceeded by 30% after two years, so that the impact of dry years in the context of water stress becomes visible. Recommendations and Outlook Processed data and results are now available to identify enhanced reservoir operation strategies for salinity reduction by changing the period of reservoir filling and release, as well as to initiate a detailed analysis of how water deficits in dry years may be reduced by improved operation regimes. Using adapted and enhanced operation rules for THC reservoirs, the local population within the lower Aral Sea basin might be supplied with more potable water of higher quality in future.     

Effect of typhoon with extreme precipitation on mountain reservoir drinking water treatment: a case study in Ningbo,China

Due to frequent drinking water pollution accidents in the past decade, it is common that mountain reservoirs were used as the source of drinking water in China. However, some coastal areas frequently suffer from typhoon with extreme precipitation, which results in the water quality deterioration of the reservoirs. The influence of typhoons with extreme precipitation on Jiaokou reservoir and the emergency treatment process of Maojiaping water treatment plant in the past three typical typhoons with extreme precipitation from the year of 2012–2015 were studied. It was found that the degradation of water quality, such as the increase of turbidity and bacteria index, may not merely appear during the events, but last for several days. Changing the dosage of water purification agent, such as coagulant and disinfectant at right time and place may be an efficient emergency water treatment process. Based on the analysis of water quality variation rule during and after the events, it was also found that emergency treatment can be fully prepared before the arrival of a typhoon with extreme precipitation. And in order to better respond to the typhoon with extreme precipitation, several suggestions are also proposed in this paper as follows: establishing vegetated buffers at right place, such as macrophanerophytes, shrub or herbage, increasing investments in infrastructure management, merging or cancelling the small-scale water treatment plants, preparing adequate water purification agent before the typhoon comes, etc.     

Taking advantage of storm and waste water retention basins as part of water use minimization in industrial sites

A methodology for water use minimization has been developed by the Clean Technology Network of Bahia over a 10 year period in joint cooperative programs with the chemical, petrochemical and copper metallurgy industries located in the largest Industrial Complex in Latin America, in Camaçari, Bahia, Brazil. The methodology comprises a set of tools including reconciled aqueous stream balances, database of aqueous streams; large scale training leading to the identification of water minimization alternatives in the processes, water reuse optimization approaches; geographical information systems as well as, consideration of the region's hydro and hydro-geological characteristics. The results of a study carried out to assess the possibility of using storm and wastewaters for industrial use is presented in this paper. The inorganic system is composed by three water reservoirs (basins) receiving stormwater contaminated with inorganic effluents, and occasionally with organics. These basins have been operated to control water flow inputs according to the capacity of the pumping outlet systems before their discharge to a submarine outfall. A mass balance was performed with historical updated data to assess water availability from the basins based on the daily volume variation and flow rate of inorganic effluent from 2001 to 2007. The study identified the possibility of recovering about 1140 m³/h of the overall 5400 m³/h consumed by the Industrial Complex at the moment. Organizational changes in the present effluent disposal and stormwater harvest systems will be required in order to maximize water recovery for industrial use.     

陕西入境旅游流外向扩散的数量化分析

在分析旅游流研究现状的基础上,以1999-2009年<中国旅游统计年鉴>、<入境游客抽样调查资料>为主要数据来源,以陕西入境旅游流外向扩散为研究对象,选取陕西入境旅游流外向扩散的15个典型旅游省市,借助SPSS、Excel等统计软件,从流量变化、流入指数等方面对陕西入境旅游流外向扩散进行数量化分析.结果表明,陕西入境旅游流主要流向上海、北京、重庆、四川和广西等经济发达地区或具有垄断性旅游资源的省市.研究结果为各省市入境旅游业区域联合发展,调整旅游产业结构提供依据.     

尾矿库在线监测系统中位移数据分析方法探讨

尾矿库的安全稳定在矿山安全生产和环境保护中具有十分重要的意义,国家已明确要求三等及三等以上尾矿库应安装在线监测系统。本文在总结我国尾矿库在线监测系统结构和建设情况基础上,分析了当前已建成系统中坝面位移或坝内位移处理方法的现状和存在的不足,并提出科学合理地分析位移数据是关系到尾矿库在线监测系统有效性和适用性的关键技术之一。在总结归纳尾矿库安全领域坝体变形和稳定安全评价方法的基础上,提出了尾矿库在线监测系统中坝面位移和坝内位移定量分析处理的新思路,指出尾矿坝变形过程的数值仿真是校核在线监测系统所得位移数据,进而有效地分析和预测尾矿坝变形趋势的重要手段之一。     

向家坝水库营养盐时空分布特征及滞留效应

向家坝建库后改变了河流原有的水动力、营养盐分布及输移条件.为研究向家坝水库营养盐分布特征及滞留效应,通过2015～2016年分季度水库水质监测结果,分析向家坝水库水体总氮(TN)、总磷(TP)和溶解性硅(SiO_3~(2-)-Si)营养盐时空分布特征、滞留量、滞留效率.研究发现,向家坝水库TN、TP和SiO_3~(2-)-Si营养盐质量浓度均值分别为0. 905、0. 034和7. 98mg·L~(-1).其中,TN质量浓度在城镇人口密集区偏大,分布主要受点源影响;磷营养盐以颗粒态磷为主,TP质量浓度在水库中自上而下沿程降低,SiO_3~(2-)-Si质量浓度分布在时空上差异较小.向家坝对TN、TP和SiO_3~(2-)-Si营养盐滞留量为2. 30×10~4、0. 146×10~4和-2. 4×10~4t·a~(-1).在不同季度,TN和SiO_3~(2-)-Si滞留量有正有负,而TP则始终表现为正滞留. TN、TP和SiO_3~(2-)-Si月平均滞留效率分别为17. 5%、32. 8%和-2. 14%.整体上实际滞留效率表现为丰水期高于枯水期,并且TP的滞留作用更为显著. TN滞留量主要受反硝化作用,以及外源负荷输入影响; SiO_3~(2-)-Si输送通量主要受径流量影响;水库运行周期以及磷的颗粒形态则是TP滞留的主要因素.向家坝水库对营养盐的滞留效应与TN和SiO_3~(2-)-Si质量浓度变化无明显相关性,而水库对TP的滞留效应使TP质量浓度在水库纵向上沿程减小,在各监测样点垂向水深上TP质量浓度则有增大的趋势.