洞庭盆地近现代非均匀沉降变化分析

结合历史文物资料、遥感数据、实测1∶50 000地形图,利用GIS的数据处理和空间分析方法,对洞庭盆地的非均匀沉降问题进行了分析,得到了各个时间段内洞庭盆地的沉降速率图,通过对各速率图的统计分析,得出非均匀沉降的时空变化规律,这对于掌握洞庭盆地的变化趋势和土地利用等方面具有重要的理论意义。     

北极海冰快速减少期间加拿大海盆上层海洋夏季淡水含量变化

北极海冰近年来快速减少,北冰洋淡水含量也出现了急剧变化。加拿大海盆作为北冰洋淡水的主要存储区域,研究其淡水含量变化对于认识北冰洋淡水收支有重要意义。本文根据2003年、2008年中国北极考察以及2004年至2007年的加拿大考察数据进行计算,发现除2006年以外,夏季加拿大海盆淡水含量在此期间每年增加1m以上厚度。增加主要发生在冬季白令海水以上的上层海水中,而在此之下,淡水含量维持在3m左右,没有显著年际差异。在2006年,加拿大海盆西部上层淡水含量略微减少,但东部和北部海域淡水含量仍略有增加。与2003年相比,2008年加拿大海盆中心海区淡水含量增加量最高可达7m。分析表明,近年来的海冰减退对加拿大海盆上层淡水含量的增加起着重要作用,北极涛动(AO)正负相位变化也是控制其淡水含量变化的一个重要因素。而降水、径流以及白令海峡入流水的变化对加拿大海盆淡水含量变化影响较小。     

近50年来淮河流域极端降水的时空变化及统计特征(英文)

Based on the daily precipitation data of 27 meteorological stations from 1960 to 2009 in the Huaihe River Basin, spatio-temporal trend and statistical distribution of extreme precipitation events in this area are analyzed. Annual maximum series (AM) and peak over threshold series (POT) are selected to simulate the probability distribution of extreme precipitation. The results show that positive trend of annual maximum precipitation is detected at most of used stations, only a small number of stations are found to depict a negative trend during the past five decades, and none of the positive or negative trend is significant. The maximum precipitation event almost occurred in the flooding period during the 1960s and 1970s. By the L-moments method, the parameters of three extreme distributions, i.e., Generalized extreme value distribution (GEV), Generalized Pareto distribution (GP) and Gamma distribution are estimated. From the results of goodness of fit test and Kolmogorov-Smirnov (K-S) test, AM series can be better fitted by GEV model and POT series can be better fitted by GP model. By the comparison of the precipitation amounts under different return levels, it can be found that the values obtained from POT series are a little larger than the values from AM series, and they can better simulate the observed values in the Huaihe River Basin.     

塔里木河流域人口-经济分布不均衡特征分析

 不均衡性是人口与经济分布最基本的属性,不均衡性过大影响区域经济的协调发展。文章利用地理联系率、Pearson相关系数、基尼系数和崔王指数分析了塔里木河流域人口-经济分布不均衡的时间特征;采用重心模型和人均GDP空间分异特征探讨了人口-经济分布不均衡的空间格局。结果表明：（1）改革开放以来,塔河流域的人口、经济分布匹配程度不断减弱,不均衡特征逐渐显著,区域经济差异已超出警戒线的范围。（2）在空间格局上,经济重心显著向东北方向集中,人口重心基本不变;人口、经济重心转移使和田、喀什、克孜勒苏柯尔克孜自治州三地州逐渐成为贫困人口集聚区,巴音郭楞蒙古自治州的库尔勒市成为经济极化中心。依据增长极理论,塔河流域经济极化中心较单一,增长体系不完善,未来需培育新的极化中心。     

流域侵蚀产沙人类活动影响指数研究——以长江上游为例

流域产沙是土壤侵蚀的重要反映, 受降雨等自然要素和人类活动的共同作用。采用退 耦理论的思想和差分方法推导出流域侵蚀产沙人类活动影响指数的简易估算方法, 并对长江 上游的金沙江、乌江、嘉陵江、岷江分别计算人类活动总体贡献率。结果表明, 各流域人类 活动对侵蚀产沙变化的贡献率达72%～97%,总体上属于抑制侵蚀的正向活动。长江上游输 沙量呈阶段梯级变化, 根据流域侵蚀产沙人类活动影响指数的距平累积变化的突变特征将 1955～2009年划分为5个阶段并分析了每个阶段人类活动的主要特点及其对侵蚀产沙的影响。 其中, 20世纪80年代中期以前河流输沙量较大, 主要与“一五”、“大炼钢铁”、“三线建设”、 农村改革前期不稳定因素等密切相关, 而70年代河流输沙量较小是受当时大搞农田基本建设 和采取“挑沙面土”、“边沟背沟”等传统水土保持措施的影响, 80年代中期后河流输沙量明 显减少, 主要受社会经济稳定有序发展、水保工程的实施及大兴水库建设等影响。     

太湖流域重污染区土地利用变化对生态系统服务价值的影响

通过对太湖流域重污染区1999年、2007年遥感影像数据解译结果的分析,获取了太湖流域重污染区主要土地利用类型的信息,分析了8 a来研究区内土地利用与覆被变化趋势,对区域土地利用类型的生态系统服务价值进行评估。结果表明,1999~2007年,太湖流域重污染区内耕地面积从2 033.53 km2减少到1 401.04 km2,而林地、建设用地、园地、水域总体呈增加的趋势,其中减少的耕地主要转化为建设用地。1999~2007年太湖流域重污染区的生态系统服务价值呈减少趋势,土地利用变化使研究区生态资产减少了2.40亿元,除气体调节和原材料以外,各单项服务功能的价值量均呈现递减的趋势。     

基于SWAT模型的汉江流域径流模拟

应用SWAT(Soil and Water Assessment Tool)分布式水文模型对汉江流域1971-2000年30年逐月径流进行了模拟.结果表明:模型模拟精度高于评价标准(模拟效率Ens>0.5,相关系数r 2>0.6),SWAT模型适用于汉江流域的径流模拟;水量平衡各要素中,30年月、年平均蒸散发量、地表径流量、土壤对地下水补给量、土壤含水变化量、地下水侧流量分别占降水量的55.97%、25.88%、17.64%、0.26%、0.25%,蒸散发是该流域水量的主要输出项;各月30年平均降水量变化趋势与地表径流量变化趋势较一致,而与基流量变化趋势一致性较差;30年流域降水量年变化趋势与地表径流量、基流量的变化趋势较一致;30年月、年地表径流量对降水的响应程度高于基流.     

Pliocene–Quaternary fluvial and aeolian records in the Souss Basin, southwest Morocco: A geomorphological model

The Souss Basin in SW Morocco is filled by Pliocene–Quaternary fluvial, fluvio-lacustrine and aeolian sediments, representing an excellent archive of palaeohydrology, palaeoclimate and the effects of crustal deformation. In general these sediments indicate stream-dominated alluvial systems, influenced by fluctuations in climate (humidity/aridity). Lakes developed within the basin around the Pliocene–Pleistocene transition and persisted into the Early Pleistocene. During this early period, relatively humid conditions are indicated by the dominance of coarse-grained sedimentation in the upper reaches of fluvial systems, the existence of large lakes and the considerable sediment thicknesses in the centre of the basin. Uplift of the surrounding mountain ranges contributed to piedmont formation by providing large amounts of coarse-grained material that accumulated at the lowland margin. Climatic deterioration in the Middle Pleistocene was accompanied by progressively more irregular and disrupted fluvial regimes. These trends were evident in the Late Pleistocene and became clearer after the mid-Holocene, with aeolian activity becoming the dominant sedimentary agent. Differences between upstream and downstream depositional regimes became marked: while coarse-grained sedimentation has characterized the upper reaches of wadi catchments, fine-grained sedimentation has prevailed downstream. Hiatuses in sedimentation throughout the Pliocene and Quaternary are marked by palaeosol horizons interbedded within the sedimentary sequences, indicating alternate vegetated (stable) and unvegetated (unstable/active) phases (biostasy and ‘rhexistasy’).     

Limiting hydrochemical factors for sustainability of water resources: The Cisjordanian experience

In Cisjordan, surface- and groundwater flow are either towards the Jordan Valley-Dead Sea-Arava Valley (the Rift) or the Mediterranean Sea. Due to upstream exploitation by riparians to the Jordan River, the historical annual flow, which fluctuated between 250 and 1100 Mm³, has declined to a mere 100-200 Mm³. The remaining flow south of Lake Kinneret is highly polluted and heavily loaded with salts. Lake Kinneret (Sea of Galilee) is one of the major water resources in the area. Annually, between 200 and 700 Mm³ reach the Lake as surface and groundwater flow. The relatively high salinity of the Lake is caused by thermomineral water discharging from springs and seepages located onshore and on the bottom of the Lake. The main factors causing deterioration of the groundwater quality in the Rift are of geogenic character. These are different types of brines, whose outflow and penetration into freshwater aquifers was triggered by overpumpage. Contemporary encroachment of seawater caused by intensive water exploitation in the Coastal Plain is manageable and reversible. However, due to lack of hydrogeological evidence, no such statement can be made about the circulation of seawater beneath the Coastal Plain and into the deep-seated Yarkon-Taninim aquifer or the upflow of brines in the Rift.The flow regimes of the different brine bodies could not be elucidated. Whether each such brine-body flows by its particular hydrological regime or whether the movement of the different bodies is intradependent or interdependent with the regional movement of fresh groundwater, remain open questions. Therefore, sustainable development of groundwater resources is clearly dependent on the elucidation of the relationship between changes in the pressure of the brine with depth and its relationship to the overlying freshwater.The average total annual recharge of all water sources in Cisjordan is 1820 Mm³, which means that the total production of water must be managed within the limits of this annual volume. During drought years, total groundwater extraction exceeds the safe yield, causing drastic lowering of water levels and upflow of saline waters from greater depths.Because of the structural complexity of aquifers and hydrochemical variability of the numerous groundwater bodies, new hydrochemical methods have been developed for the identification of groundwater bodies and for the elucidation of their origins. These methods combine macrochemical, microchemical, and isotopic evidences. By combining distribution patterns of rare earths, yttrium and stable isotopes, a complete picture of catchment lithology and the altitude and latitude of precipitation could be obtained.The area west of the Jordan River is characterized by the occurrence of transboundary surface- and groundwater basins in which fresh and saline water and brines flow across political borders between Israel and the Palestinian Authority. It is very difficult to assess separately the annual safe yield of water resources for each of the two national entities. Neither country may dispose independently of its waters and is usually at the mercy of the other riparian. There is as yet no general multilateral international treaty in force allocating the water resources of international watercourses. At present there are two rules for the management of the waters of an international drainage basin—the rule of Equitable Distribution, and the obligation Not to Cause Significant Harm. The rules of equitable distribution have tended to focus on the issue of quantities of water rather than on quality of water, which is really relevant to the issue of equitable distribution. Future negotiations on the uses of the basin will need to deal with issues of characteristic salinities and geochemical features and on their impact on equitable sharing of water resources.     

Stratigraphic evolution of an outcropping continental slope system, Tres Pasos Formation at Cerro Divisadero, Chile

Depositional slope systems along continental margins contain a record of sediment transfer from shallow‐water to deep‐water environments and represent an important area for natural resource exploration. However, well‐preserved outcrops of large‐scale depositional slopes with seismic‐scale exposures and tectonically intact stratigraphy are uncommon. Outcrop characterization of smaller‐scale depositional slope systems (i.e. < 700 m of undecompacted shelf‐to‐basin relief) has led to increased understanding of stratigraphic packaging of prograding slopes. Detailed stacking patterns of facies and sedimentary body architecture for larger‐scale slope systems, however, remain understudied. The Cretaceous Tres Pasos Formation of the Magallanes Basin, southern Chile, presents a unique opportunity to evaluate the stratigraphic evolution of such a slope system from an outcrop perspective. Inherited tectonic relief from a precursor oceanic basin phase created shelf‐to‐basin bathymetry comparable with continental margin systems (～1000 m). Sedimentological and architectural data from the Tres Pasos Formation at Cerro Divisadero reveal a record of continental margin‐scale depositional slope progradation and aggradation. Slope progradation is manifested as a vertical pattern exhibiting increasing amounts of sediment bypass upwards, which is interpreted as reflecting increasing gradient conditions. The well‐exposed, seismic‐scale outcrop is characterized by four 20 to 70 m thick sandstone‐rich successions, separated by mudstone‐rich intervals of comparable thickness (40 to 90 m). Sedimentary body geometry, facies distribution, internal bedding architecture, sandstone richness and degree of amalgamation were analysed in detail across a continuous 2·5 km long transect parallel to depositional dip. Deposition in the lower section (Units 1 and 2) was dominated by poorly channellized to unconfined sand‐laden flows and accumulation of mud‐rich mass transport deposits, which is interpreted as representing a base of slope to lower slope setting. Evidence for channellization and indicators of bypass of coarse‐grained turbidity currents are more common in the upper part of the > 600 m thick succession (Units 3 and 4), which is interpreted as reflecting increased gradient conditions as the system accreted basinward.