淮河流域近500年洪旱事件演变特征分析

为了认识淮河流域过去500年洪旱事件发生规律并鉴别当前的洪旱情势,收集并对比分析了流域实测降雨资料、重建历史雨季降雨资料、历史旱涝等级资料、历史洪旱文献记录和历史调查洪水资料等多源洪旱灾害数据。以重建历史雨季降雨资料和历史旱涝等级资料为主要依据,通过滑动平均、频率计算、小波分析和突变检验等方法,分析流域过去500年洪水干旱时空分布特征和演变规律。结果表明,17世纪淮河流域洪旱灾害最严重,但20世纪极端洪旱事件发生频次最多。淮河流域洪旱事件存在40年左右的稳定长周期,主周期从18世纪的15~20年逐渐减少到19世纪的5年周期,近20年来出现2~3年的主周期,洪旱灾害事件呈增加趋势,流域社会经济发展面临着严峻的洪旱灾害威胁。     

黄河下游漫滩洪水冲淤规律

滩地的淤积层分布记录着以往漫滩洪水的特征,即反映漫滩洪水的量级、频率和持续时间等,同时河漫滩也是预估河流泥沙、洪水灾害防治和湿地生态系统保护等的重要组成部分。根据黄河下游水文年鉴资料,分析滩地的淤积与漫滩洪水的定量关系,为未来河流泥沙预估提供依据。经分析得到大漫滩洪水在来沙系数S/Q<0.030 kg·s/m6时,主槽冲刷而滩地淤积,反之则滩槽同淤。当S/Q<0.030 kg·s/m6时,大漫滩洪水滩地的淤积量主要与漫滩系数Q_max/Q_p、上滩水量W₀和含沙量S有关;大漫滩洪水的主槽冲刷量则除了与洪水期水量W和沙量W_s有关外,还与滩地的淤积量有关。一般漫滩洪水,当来沙系数S/Q<0.023 kg·s/m6时,主槽冲刷而滩地淤积,反之则滩槽同淤。一般漫滩洪水主槽冲刷量与来沙系数S/Q和洪水期水量W有关,而滩地淤积量仅与含沙量S有关。黄河下游漫滩洪水滩地的淤积和主槽的冲刷主要发生在孙口以上河段,而孙口以下河段主槽冲刷和滩地淤积量均较少。     

Fossil hyrax dung and evidence of Late Pleistocene and Holocene vegetation types in the Namib Desert

Pollen was derived from fossil dung of herbivorous hyraxes, deposited in a rock shelter on the highest mountain in Namibia, Dâures or Brandberg, situated on the Namib Desert margin. Radiocarbon dating ranging in age between modern times and 30 000 yr BP showed it represents the first empirical pollen evidence of continental palaeovegetation during the Late Pleistocene along the western escarpment of southern Africa. The initial results indicate Last Glacial Maximum vegetation differed totally from the current pattern as vegetation types were dominated by small Asteraceae shrubs, in contrast to those of the Holocene and modern times which show more succulents, grass and woody elements (arboreal pollen). The results suggest that Cape floral communities did not reach into the tropics along the western escarpment of Africa, despite such pollen types occurring in marine cores. Copyright © 2004 John Wiley & Sons, Ltd.     

气候变化情景下北江飞来峡水库极端入库洪水预估

以北江飞来峡水库上游为研究对象,构建了网格分辨率为0.25°×0.25°的VIC(Variable Infiltration Capacity)水文模型,应用CMIP5多模式输出的降尺度结果与VIC模型耦合,对RCP2.6、RCP4.5和RCP8.5情景下未来时期(2020-2050年)飞来峡水库的入库洪水进行预估,并根据IPCC第5次评估报告处理和表达不确定性的方法来描述预估结论的可信度。结果表明,2020-2050年飞来峡水库年最大洪峰流量和年最大7日、15日洪量在RCP2.6情景下"大约可能"呈增加趋势,在RCP4.5和RCP8.5情景下"较为可能"呈增加趋势,水库防洪安全风险增大。与历史时期(1970-2000年)相比,未来水库极端入库洪水增加的可能性从大到小依次为RCP4.5、RCP2.6和RCP8.5情景,其中设计洪水100年、50年和20年一遇的洪峰流量在3种排放情景下均呈上升趋势,100年、50年和20年一遇的最大7日、15日洪量在RCP4.5情景下以上升为主,而在RCP2.6和RCP8.5情景下则主要呈减少态势。     

气候变化下淮河流域极端洪水情景预估

利用IPCC第4次评估公开发布的22个全球气候模式在A1B、A2和B1三种典型排放情景下的未来气温和降水预测结果,结合新安江月分布式水文模型,在对模型验证效果良好的基础上,参照集合预报方法,对未来90年(2010～2099年)气候变化下淮河流域的极端洪水进行预估。研究结果表明,从出现概率来看,淮河流域未来可能发生极端洪水年份的密集程度从大到小依次为A2情景、A1B情景、B1情景。A1B情景下,21世纪下半叶出现极端洪水的可能性增大,A2情景在2035～2065年以及2085年以后是极端洪水发生较为集中的时期。B1情景在21世纪70年代左右发生极端洪水的可能性较大。综合各种极端事件的定义方法,将极端洪水划定3个洪水量级。A2情景预估极端洪水的平均洪量在3种情景中最大,B1情景最小。3种情景未来一级极端洪水发生比例都比历史上偏大,A2情景下增加最多。二级极端洪水都较历史略有减少,三级极端洪水减少最显著。3种情景下各个量级极端洪水所占比例各不相同,A1B和A2情景二级以上极端洪水出现比例较大,B1情景下极端洪水量级多为三级,超1954年的一级极端洪水所占比例较小。     

淮河流域旱涝灾害致灾气候阈值

采用淮河流域内1959—2008年110个气象站的逐日降水资料,结合流域1978—2008年农作物旱涝灾害受灾面积数据,基于降水致灾因子与农作物承灾体受损程度等研究,提出旱、涝致灾气候阈值概念,在此基础上分析旱涝灾害发生的时空特征,确定淮河流域合理的旱涝致灾气候阈值区间并建立致灾气候阈值与农作物受灾面积之间的定量关系。结果表明:① 致灾气候阈值可通过计算发生旱涝事件时间段累积降水量除以1959—2008年相应时段累积降水量的平均值来定义,得到的旱、涝致灾气候阈值在不同尺度下对旱、涝灾害事件均有较好地稳定反映,可满足研究区旱、涝事件分析需求;② 洪涝致灾气候阈值与农作物受灾面积存在一致的变化趋势,而干旱致灾气候阈值与农作物受灾面积相关系数高达0.96,构建了基于干旱致灾气候阈值的农作物受灾面积预测模型。     

Characteristics and OSL minimum ages of relict fluvial deposits near Sossus Vlei,Tsauchab River,Namibia, and a regional climate record for the last 30 ka

The present end‐point of the Tsauchab River is at Sossus Vlei, 30 km into the Namib Sand Sea. Interdune deposits in three depressions west and southwest of the vlei include channel and interdune lithofacies associations but no deposits typical of river end‐points or of groundwater seepage into interdune areas. The two lithofacies associations show that the Tsauchab River extended further into the sand sea in the past. It had a well‐developed channel and a higher flow than today that caused flooding of adjacent interdune areas. OSL 4‐mm aliquot minimum ages indicate that the Tsauchab River reached 2–3 km beyond its present end‐point at ca. 25 ka and ca. 9–7 ka, and that the river was more active from 0.9–0.3 ka. The eastward migration of the river end‐point since ca. 7 ka suggests a reduction in flood magnitude accompanied by the gradual invasion of the Sossus Vlei area by dunes. The regional data indicate an additional wet interval at ca. 15 ka that is so far not recorded in the Sossus area. Copyright © 2006 John Wiley & Sons, Ltd.     

基于多源数据的近50 a玛纳斯河流域冰川变化分析

我国新疆玛纳斯河流域的冰川变化极大影响流域内及其周边地区的经济社会发展.使用国产高分一号(GF-1)遥感影像和Landsat8数据,分别通过基于多源数据的冰川识别方法和波段比值法获取了2013年玛纳斯河流域冰川信息,结合玛纳斯河流域第一次(1964年)、第二次(2009年)冰川编目数据与1998年、2003年TM影像冰川目视解译结果等四期的冰川边界矢量数据,对玛纳斯河流域1964-2013年50 a来的冰川变化特征进行了综合分析.研究结果显示:玛纳斯河流域冰川自2009年以来有略微增加的趋势,2013年冰川面积比2009年增加了10.25 km²,这在一定程度上抑制了长期以来冰川的快速消融;1964-2013年,玛纳斯河流域的冰川总体呈减少趋势;冰川面积从1964年的673.61 km²减少到2013年的512.07 km²,面积减少161.54 km²,减少23.98%;近50 a来,流域内冰川面积在海拔4500 m及以上呈净增加趋势,而在海拔4500 m以下呈净减少趋势,冰川在海拔(4000±100) m左右退缩的速率最大,高达0.5 km²·a^-1;冰川面积的减少主要体现为大量的冰舌后退和小面积冰川的快速消融,超过85%的冰川冰舌后退距离在200 m以上;该流域的冰川变化主要集中在南、北两个坡向,在南坡向上出现明显的先减少和后增加的变化趋势;1964-2013年,玛纳斯河流域的气温和降水量呈较明显的增加趋势,线性增加率分别为0.26℃·(10a)^-1和16.07 mm·(10a)^-1.研究结果表明气温的持续升高和降水量的增加分别是导致玛纳斯河流域冰川减少期和增加期形成的主要原因.     

Characteristics of diamondiferous Plio-Pleistocene littoral deposits within the palaeo-Orange River mouth, Namibia

The Orange River, the principal conduit transporting diamonds from hinterland sources to the Namibian coast in post-Cretaceous times, is characterised by an extreme wave dominated delta that has given rise to a progression of coarse rudaceous littoral deposits preserved onshore for > 150 km north of the mouth. Under the long-lived, prevailing vigorous wave, wind and northward longshore drift regimes, the Orange River outfall has been reworked into, amongst others, a series of economically viable, diamondiferous Plio-Pleistocene onshore gravel beach deposits. These placers comprise spits and barrier beaches in the proximal reach within the palaeo-Orange River mouth that, after ca. 5 km northwards, merge into extensive but narrow linear beaches that, in turn after ca. 70 km, give way to pocket beaches. Gravel and diamond size decreases northwards away from the ancestral Orange River mouth. The linear and pocket beach types have considerably higher diamond content but lower average diamond stone size than the two proximal units that are characterised by low diamond grade but comparatively large average diamond size. Given the risk of delineating low grade alluvial diamond deposits accurately, we present here sedimentological reconstructions of the subtidal, intertidal and supra-tidal facies that constitute the spit and barrier beach sequences, based largely on face mapping of exploration trenches and open-cast, mine cuts, as well as the results of large tonnage, sampling campaigns. Diamond distribution is also linked convincingly to basic littoral processes that were operational within the palaeo-Orange River mouth during the complex transgression that gave rise to the + 30 m package in Plio-Pleistocene times. In both the spit and barrier beach settings, the intertidal deposits prove to be the most promising targets whereas the subtidal sediments are the least economic. The constant raking associated with coarse, cobble–boulder-sized gravel foreshore deposits in an energetic micro-tidal wave regime increased the average diamond stone size in the intertidal deposits to 1 to 2 carats per stone (cts/stn), but the lack of fixed trapsites (no competent footwall within the palaeo-Orange River mouth at that level) prohibited the accumulation of substantially enriched diamondiferous gravels. Consequently, grades of only 1.5 to 6 carats per 100 tons (cpht) are realised. The highest grades (2 to 6 cpht) are found in the landward-facing, intertidal beach deposits on the spits where gentle reworking in that sheltered environment had somewhat enriched and preserved the diamond content. Significantly, the low average stone size of ca. 0.5 cts/stn in this lower energy setting probably reflects that of the general diamond population available at that time. In contrast, the sand-rich subtidal deposits in the spit sequence return the lowest grades (0.1 to 0.5 cpht), similar to those in the slightly younger, subtidal transgressive boulder lags of the barrier beaches. However, the stone size in the spit subtidal sediments is also low (0.1 to 0.5 cts/stn) due to the highly mobile, fine-grained character of those deposits, whereas that in the subtidal transgressive lag is large (2 to 3 cts/stn) as a result of the local, semi-permanent turbulence associated with the boulder-sized clasts in these gravel sheets. Diamond distribution is therefore also influenced by littoral facies and associated beach types, in addition to the spatial and temporal parameters that have already been documented for the onshore marine placers of the southern Namibian coast.     

The origin of sulphur in gypsum and dissolved sulphate in the Central Namib Desert,Namibia

This study investigates the sulphur source of gypsum sulphate and dissolved groundwater sulphate in the Central Namib Desert, home to one of Africa's most extensive gypsum (CaSO₄·2H₂O) accumulations. It investigates previously suggested sulphate precursors such as bedrock sulphides and decompositional marine biogenic H₂S and studies the importance of other potential sources in order to determine the origin of gypsum and dissolved sulphate in the region. An attempt has been made to sample all possible sulphur sources, pathways and types of gypsum accumulations in the Central Namib Desert. We have subjected those samples to sulphur isotopic analyses and have compiled existing results. In addition, ionic ratios of Cl/SO₄ are used to determine the presence of non-sea-salt (NSS) sulphur in groundwater and to investigate processes affecting groundwater sulphate. In contrast to previous work, this study proposes that the sulphur cycle, and the formation of gypsum, in the Namib Desert appears to be dominated by the deposition of atmospheric sulphates of phytoplanktonic origin, part of the primary marine production of the Benguela upwelling cells. The aerosol sulphates are subjected to terrestrial storage within the gypsum deposits on the hyper-arid gravel plain and are traceable in groundwater including coastal sabkhas. The hypothesis of decompositional marine biogenic H₂S or bedrock sulphide sources, as considered previously for the Namib Desert, cannot account for the widespread accumulation of gypsum in the region. The study area in the Central Namib Desert, between the Kuiseb and Omaruru rivers, features extensive gypsum accumulations in a ca. 50–70 km wide band, parallel to the shore. They consist of surficial or shallow pedogenic gypsum crusts in the desert pavement, hydromorphic playa or sabkha gypsum, as thin isolated pockets on bedrock ridges and as discrete masses of gypsum selenite along some faults. The sulphur isotopic values (δ³⁴S ‰CDT) of these occurrences are between δ³⁴S +13.0 and +18.8‰, with lower values in proximity to sulphuric ore bodies (δ³⁴S +3.1 and +3.4‰). Damaran bedrock sulphides have a wide range from δ³⁴S −4.1 to +13.8‰ but seem to be significant sources on a local scale at the most. Dissolved sulphate at playas, sabkhas, springs, boreholes and ephemeral rivers have an overall range between δ³⁴S +9.8 and +20.8‰. However, they do not show a systematic geographical trend. The Kalahari waters have lower values, between δ³⁴S +5.9 and +12.3‰. Authigenic gypsum from submarine sediments in the upwelling zone of the Benguela Current between Oranjemund and Walvis Bay ranges between δ³⁴S −34.6 to −4.6‰. A single dry atmospheric deposition sample produced a value of δ³⁴S +15.9‰. These sulphur isotopic results, complemented by meteorological, hydrological and geological information, suggest that sulphate in the Namib Desert is mainly derived from NSS sulphur, in particular oxidation products of marine dimethyl sulphide CH₃SCH₃ (DMS). The hyper-arid conditions prevailing along the Namibian coast since Miocene times favour the overall preservation of the sulphate minerals. However, sporadic and relatively wetter periods have promoted gypsum formation: the segregation of sulphates from the more soluble halite, and the gradual seaward redistribution of sulphate. This study suggests that the extreme productivity of the Benguela Current contributes towards the sulphur budget in the adjacent Namib Desert.     

Radiocarbon constraints on the Holocene flood deposits of the Ning‐Zhen Mountains,lower Yangtze River area of China

Lying athwart both the temperate and subtropical zones, the Ning‐Zhen Mountains are particularly prone to extreme floods in the summer months when cold fronts collide with the subtropics‐derived warm airmasses. The Holocene flood deposits in the region may provide a long‐term perspective on hydrographical change and its palaeoclimatic implications. Radiocarbon dates on carbonised wood preserved in flooding sediments reveal that the region has experienced a number of catastrophic floods throughout the middle Holocene. These extreme flooding events cluster into three periods: (i) 9200–8200 cal. yr BP, (ii) 7600–5800 cal. yr BP and (iii) 5200–4000 cal. yr BP, corresponding to the times when the East Asian monsoon has been intensified under warm conditions. The significant falls in flooding frequency around 8200 cal. yr BP, 5800 cal. yr BP and 4000 cal. yr BP may have resulted from substantial reduction in regional precipitation, probably associated with meridional displacement of the planetary frontal system. Copyright © 2003 John Wiley & Sons, Ltd.     

Evidence for Holocene megafloods down the Tsangpo River gorge, southeastern Tibet

Lacustrine and alluvial terraces and sediments record the extent of at least two Holocene glacially dammed lakes immediately upstream of the Tsangpo River gorge at the eastern syntaxis of the Himalaya. The larger lake covered 2835 km², with a maximum depth of 680 m and contained an estimated 832 km³ of water; the smaller lake contained an estimated 80 km³ of water. Radiocarbon dating of wood and charcoal yielded conventional radiocarbon ages of 8860 ± 40 and 9870 ± 50 ¹⁴C yr B.P. for the higher set of lake terraces, and 1220 ± 40 and 1660 ± 40 ¹⁴C yr B.P. for sediments from the lower terraces. Catastrophic failure of the glacial dams that impounded the lakes would have released outburst floods down the gorge of the Tsangpo River with estimated peak discharges of up to 1 to 5 × 10⁶ m³ s⁻¹. The erosive potential represented by the unit stream power calculated for the head of the gorge during such a catastrophic lake breakout indicates that post-glacial megafloods down the Tsangpo River were likely among the most erosive events in recent Earth history.     

长江中下游水阳江流域BZK0402孔多重地层划分及其冰后期海平面变化的沉积响应

[研究目的]开展水阳江流域标准孔BZK0402孔多重地层划分,探讨长江支流水阳江流域冰后期海平面变化的沉积响应以及古丹阳湖的成因和形成时代.[研究方法]以岩石地层为基础,在磁性地层和年代地层的双重约束下,对BZK0402孔进行多重地层划分.对比分析BZK0402孔和长江河谷、长江三角洲等邻区钻孔.[研究结果]BZK04...     

黄河下游非恒定输沙数学模型——Ⅱ模型验证

利用所构建的非恒定输沙数学模型,对黄河下游铁谢至孙口河段内的1977年高含沙洪水、1982年大水少沙型洪水以及1996年典型洪水进行了数值模拟.模拟结果证明了数学模型的可靠性,表明该模型不仅能模拟黄河下游河道一般洪水和高含沙洪水的水沙传播、水位变化及河床变形等,而且对模拟现行严重萎缩河道内的洪水演进及河床冲淤特性也有较好的适应性.     

延河流域雨洪特性及洪水预报

延河是黄河的一级支流，流经安塞、延安、延长等陕北南部地区的重要城镇，是引发该地区城镇洪水的主要河流，因此，延河洪水预报对这些城镇的防洪安全具有重要意义。在分析延河流域雨洪特性的基础上，以提高大洪水的预报精度为主、适当兼顾中小洪水的原则，采用具有成因概念的系统模型和相关图法，建立了以延安市为重点、包括安塞及延长县城的延河区段洪水预报方案，可供作业预报试用。     

新疆阿克苏河流域洪水演变趋势研究

全球气候变暖将加剧水循环,增大洪水风险.阿克苏河流域位于天山南坡,是北半球中纬度典型的高山流域.本流域不仅有暴雨洪水、冰川和积雪融水造成的洪水,而且还有冰川溃决突发洪水.以阿克苏河的两条支流库玛拉克河和托什干河为研究对象,利用块最大值抽样方法(block maximum)和超定量阈值(peak over thresho...     

“蒸发悖论”在黑河流域的探讨

利用黑河流域12个气象站点1960-2010年的气象资料,运用FAO Penman-Monteith模型计算潜在蒸散量,采用旋转经验正交函数、Mann-Kendall检验等方法系统分析了过去51 a间潜在蒸散量及气温的变化趋势,重点对"蒸发悖论"在黑河流域的规律进行分析.结果表明:根据潜在蒸散量的旋转经验正交函数分区结果,黑河流域可以划分为4个子区."蒸发悖论"仅于1960-1993年存在于黑河流域河西走廊区(Ⅱ区、Ⅲ区);其它各区无"蒸发悖论".1994-2010年由于潜在蒸散量的显著上升,河西走廊区"蒸发悖论"消失.1993年是黑河流域潜在蒸散量变化趋势的一个转折点,1994-2010年黑河流域的潜在蒸散量表现为统计显著的上升趋势.风速的变化是影响黑河流域河西走廊区"蒸发悖论"出现和消失的重要因素.     

额尔齐斯河流域上游地区近50 a来气温和降水变化的DFA分析

为查明新疆境内额尔齐斯河流域年及季节性气温和降水变化规律,并对未来的可能变化趋势做出预测,基于去趋势波动分析法（DFA）对流域近50 a来的气温、降水序列的平均值和极端值进行分析. 研究表明,年降水及春、夏的降水序列有较好的长程相关性,在较长时间尺度内均有继续保持原有趋势的可能,即年降水继续增加,春、夏降水维持稳定;秋、冬季降水则呈现弱持续性和强随机性,在短时间尺度上保持现状,长时间尺度上则存在改变的可能. 年均温及夏、秋、冬温也将继续保持升温的趋势,春季长时间尺度上存在改变的可能. 流域内温度和降水都将保持增长的趋势,而且温度的持续上升相对降水具有更高的可能性. 由DFA方法确定的极端阈值及相应极值序列显示：20世纪80年代以来,极端高温和极端降水事件开始增多,且量值增大,准周期变短,但极端高值并没有显著提高;极端低温事件的发生次数减少显著,平均值增大,同时低温极值增高明显,冬季气温对全球变化的响应更为敏感.     

黑河流域地下水同位素年龄及可更新能力研究

通过对黑河流域地下水的放射性同位素如氚(T)和¹⁴C的测定, 对该流域浅层和深层地下水的年龄以及其更新速率进行了估算. 结果表明: 整体上看, 从黑河流域的上游、中游至下游, 浅层和深层地下水年龄逐渐增加, 地下水更新速率也逐渐增大. 其中, 黑河上游浅层和深层地下水平均更新速率分别为1.96%·a^-1和1.76%·a^-1, 可更新能力最强; 中游浅层和深层地下水平均更新速率为1.25%·a^-1和0.68%·a^-1, 可更新能力次之; 下游浅层和深层地下水平均更新速率分别为0.74%·a^-1和0.18%·a^-1, 可更新能力最差. 黑河流域不同地带地下水由于循环条件的不同, 浅层和深层地下水年龄存在较大的差异. 其中, 中游山前平原补给条件较好, 浅层和深层地下水年龄较小; 中、下游远离河道地区浅层和深层地下水补给条件差, 显示了更老的年龄. 黑河流域埋深40 m以上的浅层地下水平均更新速率(1.13%·a^-1)高于埋深40~100 m之间的中层地下水(0.65%·a^-1)以及埋深100 m以下深层地下水(0.55%·a^-1). 因此, 在黑河流域地下水开发过程中要合理开发浅层地下水, 适当缩减开发深层地下水.     

长江三角洲古河谷区冰后期孢粉组合及古气候意义

依据长江三角洲古河谷区典型钻孔CSJA6孔中冰后期孢粉分布情况,结合有孔虫分析以及6个样品的AMS 14C年龄,自下而上初步建立了冰后期3个有时间标定的孢粉组合,分别为:Ⅰ. Quercus-Lipuidambar-Artemisia-Polypodiacea组合,时代属于早全新世;Ⅱ. Quercus-Castanopsis-Cyperaceae-Pteris组合,时代属于早-中全新世;Ⅲ. Quercus-Ulmus-Artemisia-Polypodiacea组合,时代属于中-晚全新世.3个孢粉组合带所反映的古气候演变过程为凉干-热湿-温干,这与中国的气候大环境较为一致,且与本区前人研究成果亦做了相应的对比,依然具有较好的可对比性.