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Spatio-temporal patterns of hydrological processes and their responses to human activities in the Poyang Lake basin,China

Abstract

Poyang Lake is the largest freshwater lake in China, and plays a major role in flood mitigation, restoration and conservation of the ecological environment in the middle Yangtze River basin. Sediment load and streamflow variations in Poyang Lake basin are important for the scouring and deposition changes of this lake. However, these hydrological processes are heavily influenced by human activities, such as construction of water reservoirs, and land-use/land cover changes. By thorough analysis of long series of sediment and streamflow obtained from five major hydrological stations, we systematically investigated the spatial and temporal patterns of these hydrological processes and the hydrological responses to human activities using the Mann-Kendall trend test, the double cumulative mass curve and the linear regression method. The results show: (1) no significant change in streamflow followed by an increasing tendency after the 1990s that turns to be decreasing about 2000; and (2) a sharp increase of sediment load during the late 1960s and 1970s triggered by extensive deforestation (during the “Cultural Revolution” in China) followed by a tendency to decrease after the early 1980s. Construction of water reservoirs has greatly reduced the sediment load of the Poyang Lake basin, and this is particularly the case in the Ganjiang River, where the sediment load changes may be attributed to the trapping effects of the Wan'an Reservoir, the largest water reservoir within the Poyang Lake basin. There is no evidence to corroborate the influence of water reservoirs on the streamflow variations. It seems that the streamflow variations are subject mainly to precipitation changes, but this requires further analysis. The current study may be of scientific and practical benefit in the conservation and restoration of Poyang Lake, as a kind of wetland, and also in flood mitigation in the middle Yangtze River basin that is under the influence of human activities.

Citation Zhang, Q., Sun, P., Jiang, T. & Chen, X.-H. (2011) Spatio-temporal patterns of hydrological processes and their hydrological responses to human activities in the Poyang Lake basin, China. Hydrol. Sci. J. 56(2), 305–318.     

The Influence of Weathering on the Engineering Properties of Dunites

Weathering processes cause important changes in the engineering properties of rocks. In this study, dunites in the Bursa region in western Turkey were investigated and the changes in engineering properties due to weathering were evaluated. The studies were initiated with field observations including measurement of the characteristics of discontinuities such as spacing, aperture, fill material, roughness, and Schmidt hammer rebound value. Subsequently, laboratory studies were conducted in two stages. The first stage comprised mineralogical, petrographic, and chemical analyses. The second stage included physicomechanical tests to determine specific gravity, unit weights, water absorption, effective porosity, uniaxial compressive strength, P-wave velocity, and slake-durability index. According to these evaluations, the changes in engineering properties were determined to be mostly related to serpentinization at every stage of weathering. The most suitable parameters for characterizing the degree of weathering of the studied dunites are loss-on-ignition values, specific gravity, unit weight, water absorption, and effective porosity.     

综合处理办法在城市复杂地段桥桩施工中的应用

在北京市德内大街桥桩施工过程中,不仅遇到交通拥堵．场地狭小．地上地下障碍物等多种不利条件．而且在拟施工的桩位处遇到大量原有河道的加固材料,物品种类之多、数量之大、埋深之厚,实属罕见,施工条件极差、施工难度极高,施工单位最终通过采取多种办法、措施解决了这些难题,圆满的完成了桥桩施工任务。本人认为在旧城复杂地段施工时,综合处理措施具有很大发展空间,值得深入研究发展,在旧城改造的类似工程中具有一定借鉴作用。     

河南栾川地区铅锌矿床地质和硫同位素地球化学

河南栾川地区是我国著名斑岩钼矿集区,近年铅锌矿勘查取得重要进展,但对铅锌矿成因认识分歧颇多。研究表明,栾川地区铅锌矿产在燕山期斑岩钼矿床外围,矿区地层为中元古界官道口群和新元古界栾川群碳酸盐岩-碎屑岩沉积变质建造,地层中侵入有晋宁期辉长岩、正长岩和燕山期酸性斑岩,铅锌矿呈脉状或透镜状,发育3种类型:受燕山期斑岩与元古界钙质地层接触带控制的夕卡岩型铅锌矿、受北西西向层间断裂构造控制的脉状铅锌矿和受北东或近南北向张-张扭性断裂控制的脉状铅锌矿。铅锌矿石中硫化物δ~(34)S_(V-CDT)为近零的正值(骆驼山0.37‰～4.20‰、赤土店-0.32‰～8.30‰、百炉沟-1.20‰～10.90‰、冷水北沟0.70‰～12.10‰),岩浆来源硫特征明显;夕卡岩型铅锌硫化物的δ~(34)S_(V-CDT)与本地斑岩型钼矿石中硫化物的δ~(34)S_(V-CDT)(1.24‰～3.30‰)极为相近,脉状铅锌硫化物的δ~(34)S_(V-CDT)与斑岩型钼矿石中硫化物重合,但有地层中硫(δ~(34)S_(V-CDT)为12.43‰～18.63‰)的影响。总体上δ~(34)S_(黄铁矿)>δ~(34)S_(闪锌矿)>δ~(34)S_(方铅矿),指示矿石中主要硫化物矿物硫同位素分馏基本达到平衡,赤土店铅锌矿石中共生方铅矿与闪锌矿的硫同位素温度计指示硫化物矿物沉淀温度较高(388.29℃)。河南栾川地区铅锌矿主体应为受燕山期构造-岩浆作用控制的中高温热液铅锌矿床。     

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2008—2022年上海大莲湖湿地营养盐时空分布特征、水质评价及来源解析

为了解大莲湖湿地区域水体营养盐的时空分布特征及污染来源,本文系统汇整了2008—2022年大莲湖湿地的水质数据,于2021—2022年丰水期和枯水期针对6种不同土地利用类型进行水样采集分析,也于2021年平水期进行各指标的24 h昼夜监测分析。年际研究结果表明,2008—2022年期间大莲湖湖区总氮(TN)浓度基本处于《地表水环境质量标准》(GB3838—2002)Ⅳ～Ⅴ类水质标准,在2009年枯水期达到最大值(2.97 mg/L);湖区氨氮浓度近年来满足Ⅲ类水质标准;总磷浓度在2021年的丰水期达到最大值0.79 mg/L,超过Ⅴ类水标准限值0.4 mg/L。湖区水质较生态修复之前有所好转,但营养盐浓度依旧处于较高水平。整体趋势与淀山湖的营养盐浓度基本一致,说明上游淀山湖入湖来水可能是造成大莲湖营养盐增高的原因之一。季节性研究结果显示,水体各类指标存在一定季节性差异,枯水期略劣于丰水期。不排除入湖河流带来的污染对大莲湖湿地区域产生影响,丰枯水期鱼塘和荷花塘水体营养盐和有机物质超标现象突出,尤其是鱼塘点位TN浓度是Ⅴ类水标准限值2.0 mg/L的2～4倍。24 h昼夜监测结果发现,大部...     

秦巴山区重晶石与毒重石矿床成矿特征研究

秦巴山区按地质成矿特征可划分大巴山、平利、南秦岭三个区。重晶石与毒重石矿床分三条成矿带 :南带为毒重石矿带、北带与中带为重晶石矿带 ,成矿具有多期作用 ,含火山喷发、大陆边缘沉积、裂谷与脉体成矿叠加。本区找矿前景是乐观的。     

2012年8月中旬四川大暴雨的数值模拟及地形影响试验

利用WRF模式对2012年8月17~18日四川出现的一次大暴雨过程进行模式模拟和诊断分析,并通过对地形敏感性试验讨论川西高原至川东过渡带陡峭地形对此次暴雨的影响。结果表明,WRF基本成功模拟出2012年8月中旬四川中部大暴雨过程,对环流形式预报与实况较为一致。此次过程水汽来源台风低压及副高外围携带的水汽。川中云团发展阶段对应四川中部多个站出现强降水,该对流云团发展是引发本次降水的重要因素,而对流层中低层高温高湿环境对对流云团发展提供有力的环境。地形敏感性试验表明,陡峭地形高度与降水强度呈正比,通过影响陡峭地形周边物理量特征场分布从而影响暴雨区降水强度;相对湿度的影响小于温度对降水强度的影响作用。