Hydrological alterations from water infrastructure development in the Mekong floodplains

The Mekong floodplains, which encompasses the region from Kratie Township in Central Cambodia to the Vietnamese East Sea, is a region of globally renown agricultural productivity and biodiversity. The construction of 135 dams across the Mekong basin and the development of delta‐based flood prevention systems have caused public concern given possible threats on the stability of agricultural and ecological systems in the floodplains. Mekong dams store water upstream and regulate flow seasonality, while in situ flood prevention systems re‐distribute water retention capacity in the floodplains. The main aim of this paper is to evaluate possible impacts of the recent development of both hydropower dams and flood prevention systems on hydrological regimes in the Mekong floodplains. An analysis of measured daily and hourly water level data for key stations in the Mekong floodplains from Kratie to the river mouth in Vietnam was conducted. Hydropower dam information was obtained from the hydropower database managed by the Mekong River Commission, and the MODIS satellite imagery was used to detect changes in flooding extent related to the operation of flood prevention systems in the Vietnam Mekong Delta. Results indicate that the upper part of the floodplains, the Cambodian floodplains, may buffer upstream dam impacts to the Vietnam Mekong Delta. Flood prevention up to date has had the greatest effect on the natural hydrological regime of the Mekong floodplains, evidenced by a significant increase of water level rise and fall rates in the upper delta and causing water levels in the middle delta to increase. The development of flood prevention systems has also effected spatial distribution of flooding as indicated via a time series analysis of satellite imagery. While this development leads to increase localized agricultural productivity, our historical data analysis indicates that development of one region detrimentally affects other regions within the delta, which could increase the risk of future conflicts among regions, economic sectors and the ecological value of these important floodplains. Copyright © 2016 John Wiley & Sons, Ltd.     

水库对河流水温影响的评价指标

水库对其下游河道水温影响是目前水电工程环境影响评价的重要内容之一。在分析水库干扰后的河流水温波动特征的基础上,构建了水库对其下游河道水温影响的评价指标:基线偏离指标、相位偏移指标和极值变幅指标。对各指标含义进行界定并建立其函数表达式,提出水库对河流水温影响的指标评价方法。选取黄河上游已开发梯级水库为例,应用提出的指标评价了该梯级水库对河流水温的时空影响。研究表明:对于不同调节类型的水库,指标能够敏感地辨析水库对河流水温季节性波动、水温滞迟和均化作用等影响;也可判别其对水温影响的主要特征。此外,针对受影响河段的不同位置分析各指标的波动趋势,可揭示梯级水库对其下游河道水温累积影响的变化程度。提出的指标具有通用性,可为其它流域开展水库水温影响研究提供科学参考。     

澜沧江—湄公河流域跨界含水层研究

跨界含水层由位于不同国家的含水层组成,是地下水资源系统的重要组成部分。妥善管理并公平合理地利用跨界含水层,对促进可持续发展及国家之间的睦邻友好关系有着重要意义。通过分析澜沧江—湄公河流域水文地质条件,划定流域的跨界含水层系统,并对地下水资源与环境问题进行探索,提出跨界含水层综合评价指标体系,结合澜沧江—湄公河流域4个跨界含水层相关的指标进行了综合评价。本次研究,对管理澜沧江—湄公河流域跨界含水层,建设和谐的东南亚国际环境有着重要意义。     

基于卡方变换的中分辨率遥感影像土地覆盖变化对象识别方法

该文旨在探讨中分辨率遥感影像的土地覆盖变化对象识别方法。首先基于植被-不透水层-土壤(VIS)模型,参考OIF指数的信息量进行对象特征指标选取,基于过分割和欠分割指数确定最优分割尺度,对两期SPOT影像进行多时相分割,然后利用卡方变换方法自动选择阈值,进行植被、不透水层、土壤和水体4种土地覆盖类型之间的变化对象识别。精度评价表明,随着对象特征指标包含信息量的不断增加,检测结果的总精度不断提高,其中对影像所有特征指标进行主成分分析并选择前3个主成分作为特征指标组合对土地覆盖变化对象进行识别的总精度最高,为93.9%,Kappa系数为0.824,证明了该方法的有效性。     

A Conceptual Framework for Enhancing the Utility of Rainfall Hazard Forecasts for Agriculture in Marginal Environments

Semi-arid and dry sub-humid areas (especially in the tropics) are characterized by high inter-annual and intra-seasonal rainfall variability. Agriculture, which employs the bulk of the rapidly increasing populations, is largely rain-fed, low-input based and highly resource dependent. Recent spates of drought have, therefore, exacerbated the now-too-familiar specter of famine and starvation in these areas with glaring examples being the recurring episodes in sub-Saharan Africa since the great Sahel drought of 1969–1973. A great need for accurate and timely hazard forecast products in aid of agriculture thus exists.Several schemes are currently employed by various agencies around the globe in this direction. There does remain, however, a gap between product provision and user expectations. This paper examines this gap suggesting a five-point framework within which it can be addressed as an action agenda for the climate science community. The paper posits that changes are possible to existing methodologies (related to three of these points), which, within the context of current science, can greatly enhance the utility of forecast products for agriculture in marginal areas. The remaining two points have, however, been identified as requiring additional applied research and necessary pointers for addressing these issues are provided. First is the need for appropriate impact-related indicators for intra-seasonal and interannual rainfall variability that are easy to compute, amenable to forecasting and follow closely the experiences of farmers in marginal areas. The second is a consideration of appropriate forecast information formatting and communication medium that guarantee effective feedback between forecast producers and users. Specific examples of the status quo and of work currently underway are cited from southern Africa – a region currently attracting international attention as a result of recent droughts and the threat of famine.     

基于模型试验的海洋核动力平台定位系统解脱作业关键指标分析

海洋核动力平台定位系统采用软刚臂单点系泊方式,属于多铰连接的单点系泊装置。定位系统在长期海上运营过程中,会面临结构维护、改造、更换等作业,解脱作业的安全性是定位系统乃至核动力平台安全的重要组成。借鉴国内外海洋石油平台解脱作业的成功案例,首先给出了核动力平台定位系统解脱作业的流程,并结合解脱作业故障树的风险传递路径给出关键风险指标;然后基于相似理论搭建了定位系统1∶9缩尺比模型试验平台,真实模拟了定位系统全流程解脱作业,验证了定位系统解脱作业的可行性与有效性;基于实时测量数据分析提升缆绳在限位状态与解脱作业时的张力响应、法兰解脱时系泊腿下部万向节振动响应、系泊刚臂下放姿态等关键指标。研究结果表明物理试验模拟方法可以准确表征解脱作业过程的关键节点,并为量化作业指标、优化作业流程提供数据支持,同时相关试验分析方法可以为其他海洋装备的解脱、安装等提供参考。     

云南省兰坪县凤岩山铅锌铜多金属矿地质特征及成因探讨

凤岩山铅锌铜多金属矿位于兰坪断陷盆地中部,具有良好的成矿条件和找矿前景。文章通过对矿区地质背景条件、地质特征、地球化学异常特征、矿体特征、矿石特征的分析,推断矿床成因为后期热卤水为主改造叠加形成,属沉积一改造层控型矿床。     

Effects of different organic residues on rice yield and soil quality

Calcaric regosols are a valuable land resource, distributed widely across western China. Soil quality has deteriorated considerably in recent years owing to the blind pursuit of economic benefits. A 2-year field experiment was carried out to evaluate the effects of using spent mushroom compost, leguminous plant (Vicia sepium L.) compost, and a combination of the two (at a 1:1 and 2:1 ratio), on rice yield and soil quality in a suburb of China. Vicia sepium L. composted with spent mushroom compost at a 1:1 ratio produced the highest grain and stover yield, grain and stover phosphorus concentration, and phosphorus uptake of rice; they were 56.5%, 93.2%, 89.3%, 198.6% and 22.2% greater than control soil, respectively. The 2:1 ratio (Vicia sepium L.: spent mushroom compost) produced the highest grain N concentration, stover N concentration, and N uptake; they were 31.6%, 31.4%, and 40.7% higher than control, respectively. Soil physical, chemical, and environmental properties were improved with the application of Vicia sepium L. composted with spent mushroom compost at a 2:1 ratio. In particular, soil water-stable aggregates, organic carbon, particulate organic carbon, total nitrogen, available potassium, and cation exchange capacity increased, whereas bulk density, pH, and phytoavailable heavy metals decreased. This organic treatment is beneficial to improve soil quality indicators, and contribute to soil restoration.     

Structure and dynamics of demersal fish assemblages over three decades (1985–2012) of increasing fishing pressure in Guinea

In a context of growing fishing pressures and recommendations for an ecosystem approach to fisheries, there is a need to monitor changes in fish communities over time. In this study, we analysed data from scientific trawl surveys carried out on the continental shelf off Guinea between 1985 and 2012. We performed factorial analyses and calculated biodiversity indices to characterise the changes in the structure and composition of fish communities that occurred over the 28-year period in this area, particularly given intensive fishing activities. We show that, over the study period, fish communities on the Guinean shelf were structured primarily according to spatial factors, with temporal changes being less pronounced than expected. However, a temporal analysis of biodiversity indices and species dominance showed that the intensification of fishing had significant effects on the general ecological features of the fish assemblages under study. There was a decrease in fish density and in mean trophic level. In addition, there were changes in species dominance, whereby large, slow-growing species with high commercial value were gradually replaced by smaller, fast-growing species of lesser commercial interest. These results from field observations are in line with some conclusions from previous modelling studies in the same geographical area, and provide further support for the hypothesis of a progressive ‘ecosystem effect of fishing’ occurring in Guinean waters.     

基于PSR框架的土地质量指标体系研究进展与展望

基于"压力-状态-响应(Press-State-Response,PSR)"模式的土地质量指标体系是国际土地科学研究的热点问题。我国经济的快速增长和土地退化的严峻形势要求建立能够衡量土地质量变化的指标体系。介绍了基于PSR框架的土地质量指标体系的来源、基本概念、评价框架和研究计划。介绍了国际土地质量指标研究计划中提出的养分平衡、产量差额、农业土地利用强度与利用多样性、土地覆被、土壤质量、土地退化、农业生物多样性、水质量、林地质量、牧草地质量、土地污染等11项土地质量指标。在总结、分析国内外土地质量指标体系研究的最新进展和研究不足基础上,提出未来我国有关部门在土地质量方面的研究趋势与建议。