中国寒区水文学研究的新阶段——记我国杰出寒区水文学家叶柏生研究员的创新与贡献

我国杰出的寒区水文学家叶柏生研究员不幸因公殉职.选取了叶柏生研究员若干代表性研究成果,包括与他人的合作研究成果,重点从冰川水文、冻土水文和区域水文变化三方面总结了其对寒区水文学发展所做的创新与贡献.文章列出了每项研究成果的核心内容,并给予了简要评述.所选成果中,冰川水文方面研究涉及冰川对河川径流的调节作用、冰川径流对气候变化的响应机理等;冻土水文研究着重介绍了多年冻土变化对流域径流过程及其变化影响方面的系统性成果;区域水文变化研究方面,选取了降水观测误差修正、气候变化对区域径流的影响等方面的创新成果.这些研究成果极大地提高了我国在世界寒区水文学研究的地位,对认识寒区水文过程及气候变化对水资源的影响具有重要科学意义.

气候变化对水生生物区系,生态系统结构和功能的影响

气候变化将引起水生生物地球化学过程(包括碳动力变化)、水生食物网结构、动态和生物多样性以及初级和次级生产力的显著变化,影响水生哺乳动物和水禽的分布范围、分布型、栖息地质量和数量。未来永久冻土融化的增加将使营养物、沉积物和水生系统的碳负荷增加,对淡水的化学成分产生正负作用。营养物和碳富集将促进营养物循环和生产力提高,改变含碳痕量气体的形成和消耗。因此,作为碳汇或源的水生生态系统的状态将发生改变。气候变化对北极大部分地区淡水生态系统的生物多样性也具有显著影响,影响和响应的大小、程度和持续时间将随系统和位点而异。对水生哺乳动物和水禽的影响包括迁徙路径和时间改变,由于疾病和寄生虫感染而可能使死亡率升高、生长和生产力下降,以及或许发生栖息地适合性和可获得时间变化。

气候变化对北极淡水生态系统的水文生态学影响

北极淡水-陆地系统变暖的速度通常大于全球平均速度,特别是在秋季和冬季。许多低温层组分的减少或消失,以及从多雪到多雨气候类型的转变将对淡水生态系统产生多种影响,其中最显著的是春汛优势地位的下降和河冰融解强度的变化。无冰期的延长、气温和水温的升高、高蒸腾植物的增加,以及永久冻土融化引起的渗透性增加将使植物蒸腾作用或土壤水分蒸发蒸腾损失总量增加,从而造成地表水位和面积下降。冰盖和永久冻土的减少、水温升高和植被类型变化对水化学的影响通常是使激流和静水群落生产力增加。冰盖和淡水流量或水位的变化导致北极圈动物栖息地可获得性和质量的某些方面的变化。

气候变化对北极淡水生态系统及渔业的影响:北极气候影响评估(ACIA)的背景,基本原理及做法

北极的气候变化和紫外辐射水平的变化将具有深远的影响,会影响各营养级的水生物种、构成其生境的物理和化学环境以及作用于淡水生态系统和其内部的过程。诸如温度和降水之类的气候变量与淡水生态系统的相互作用高度复杂并能够以难以预测的方式在生态系统中蔓延。这部分是由于对北极淡水生态系统及其与气候和其他环境变量的相互关系缺乏了解,同时也由于北极地区缺乏长期的淡水监测点和综合的水文—生态学研究计划。本专刊中的文章是25名国际专家和他们各自的网络关于北极淡水水文学和相关的水生生态系统进行的分析的摘要,该摘要最初在2005年作为北极气候影响评估(ACIA)的"第8章——淡水生态系统和渔业"发表。这些文章广泛地概述了北极各种淡水系统的一般水文学和生态学特征,包括对每一个ACIA地区的描述,后面回顾了全新世期间淡水系统的历史变化。接着是气候变化对大尺度水文生态学、水生生物和生态系统结构和功能,以及北极鱼类和渔业影响的评估。还讨论了潜在的增效效应和累积效应以及紫外辐射和污染物的作用。文章利用环北极地区的案例研究结果说明了许多影响的性质和复杂性,以及重要的临界响应(即:那些产生分阶段影响和/或非线性影响的响应)。本期最后总结了关键的发现,并列举了科学认识方面的空白,以及与政策有关的建议。

与气候变化相关的北极淡水生态系统的一般特征

在北极附近存在的两大类淡水生态系统,即:激流(流水;如:河流、溪流、三角洲及河口)和死水(静水;如湖泊、池塘及湿地)生态系统,它们在大小、丰度及生物群方面存在着巨大的差异。北极的气候,其许多的组分沿纬度梯度呈现出强烈的变化,直接影响这些水生系统中的各种物理、化学及生物学过程。此外,北极气候通过控制陆地水文系统和过程,特别是那些与诸如永久冻土、淡水冰和雪聚积/融化等低温层组分有关的,而产生其它间接的生态影响。北极淡水系统的生态结构和功能也受外部过程和条件的控制,特别是在主要北极河流源头和毗邻海洋环境中的那些。物理、化学及生物组分穿过互连的死水和激流淡水生态系统的运动是北极淡水生态的主要决定因素。

北极淡水生态系统的历史变化

各类基于生态系统的气候替代数据一直用于评估北极过去的变化。虽然由于河流物质的持续性重新建构使流水生态系统的记录相对缺乏,但可通过高质量静水生态系统数据的组合,回溯到环北极地区的更新世末期和冰川消失时期。总之,可以部分地归因于冰川覆盖收缩效应的变化引起的全新世的气候变化,使北极的水文和淡水生态系统产生了重要的时空变化。特别值得注意的是,在长期的润湿时期,北部泥炭地得到了大规模扩展。较近期的湖泊生物区和沉积学数据揭示了在过去1～2个世纪期间出现的一般性气候变暖趋势,并且表明了淡水特征,譬如冰盖持续时间和热量层化的主要变化。这些数据为预测和量测气候变化对未来的影响提供了一个极好的依据基线。

Evolution of Mount Cameroon volcanism: Geochemistry, mineral chemistry and radiogenic isotopes(Pb, Sr, Nd)

Mount Cameroon volcano has erupted several times in the 20 th Century with documented eruptions in 1909,1922,1954,1959,1982,1999 and 2000.Evidence of historic volcanism is represented by several older lava flows and lahar deposits around the flanks of the volcano.This study aims to assess the evolution of Mount Cameroon volcanism through its eruptive history via interpretation of mineralogical,whole rock geochemical and Pb,Sr,Nd isotope data generated from historic and recent lava flows.In this study,samples were collected from the 1959,1982,1999 and 2000 eruptions and from several historic eruption sites with unknown eruption dates.Evaluation of major and trace element data demonstrates that Mount Cameroon is geotectonically associated with within-plate Ocean Island Basalt Settings.More than 90%of the studied historic lavas(n=29)classify as tephrites and basanites whereas the modern lavas(n=38)are predominantly trachybasalts,demonstrating evolution from primitive to evolved lavas over time typically in response to fractional crystallization.Petrographically,the lavas are porphyritic with main mineral phases being olivine,clinopyroxene,plagioclase feldspars and Fe-Ti-Cr oxides.The 1982 lavas are predominantly aphyric and dominated by lath-shaped flow-aligned plagioclase in the groundmass.Olivine chemistry shows variable forsterite compositions from Fo60-89.Clinopyroxenes vary from diopside through augite to titanaugite with chemical composition ranges from Wo45En32Fs7 to Wo51En47Fs17.Plagioclase feldspars vary from labradorite(An567 O)to bytownite(An80-87).For the Fe-Ti-Cr oxides,calculated ulvospinel component shows a wide variation from ulv38-87.CIPW-normative classification on the Di-Ol-Hy-Qz-Ne system shows that all Mount Cameroon lavas are nepheline-normative(Ne ranges from4.20 wt.%to 11.45 wt.%).Radiogenic isotope data demonstrate that Mount Cameroon lavas are HIMU(or high μ=238U/204Pb),characterized by 206Pb/204Pb=20.19-20.46,207Pb/204Pb=15.63-15.69,208Pb/204Pb=40.01-40.30,87Sr/86Sr=0.70322-0.70339(εsr=-21.37 to-18.96)and 143 Nd/144 Nd=0.51276-0.51285(εNd=+2.29 to+4.05).The historic lavas show stronger HIMU signature relative to the modern lavas,suggesting evolution towards less HIMU signatures over time.This study has revealed that Mount Cameroon volcanism has evolved from primitive magmas characterized by stronger HIMU signatures with high 206/204Pb and 208/204Pb isotopes,low SiO2 and high Mg,Ni,Cr content towards lower HIMU signatures with relatively higher SiO2,lower Mg,Cr and Ni compositions.The geochemical and isotopic changes,which account for the evolution of magmatism on Mount Cameroon occur over long periods of time because all the modern lavas erupted within the last 100 years are isotopically homogeneous,with very limited variation in SiO2 compositions.

Assessment of Surface Water Quality of Bétaré-Oya Gold Mining Area (East-Cameroon)

To assess the water quality in the locality of Bétaré-Oya affected by an intensive artisanal and semi mechanized mining activities, 71 samples were collected from sixteen points during the 2015-2016 hydrological year. These points include: three in Lom river which is the main stream of the study area, five in Mari river which is one of the left bank tributaries of the Lom, in Bétaré-Oya and eight in the left and the right bank of Mari. Different physicochemical parameters such as pH, electrical conductivity (EC), alkalinity, turbidity, total suspended solids (TSS), cyanide (CN-), major elements and heavy metals (Pb, Zn, Cd, Fe, Cu, As, Mn and Cr) were analyzed. Water Quality Indices (WQI), Heavy metal Pollution Index (HPI), sodium adsorption ratio (SAR) and percent sodium (Na%) were also computed to evaluate the suitability of water for drinking and irrigation. The results showed that the surface water from Bétaré-Oya was acidic to basic (5.40 < pH < 8.84), weakly mineralized (11.60 < EC < 122.10 μS/cm) with a high concentration of TSS (2 < TSS < 8996.00 mg/L) and turbidity (1.22 to 4758.00 NTU). The WQI scores show excellently to unsuitable quality in almost all the sampling sites. The water quality is found to be most deteriorated in Lom river and in the downstream of Mari river where an extensive mining activity is carried out, with the high WQI value of 5137.40. Based on heavy metal pollution index, the mean value was 1195.36 and thus under the critical pollution index. We thus notice a serious physical degradation by organic and mineral suspended particles as well as chemical degradation by heavy metals. This results from mining activities in the Lom river and its main tributaries such as the Mari river in the upstream part of the Sanaga basin. According to the percentage of sodium and SAR, these waters can be used for irrigation purposes in almost all types of soils.

Stream temperature dynamics in Nam Co basin, southern Tibetan Plateau

Stream temperatures are sensitive to climate change and runoff regime variations. A comprehensive understanding on the effects of glacial melting on the stream temperatures are important in the Tibetan Plateau, of which contains the largest ice volume outside Polar Regions. This study documented the high-resolution stream temperature thermal regimes from glacier-fed and non-glacial rivers at four sites, versus a high-resolution glacier mass balance monitoring at Zhadang glacier, during summer melt seasons from 2007-2009 in the Nam Co basin of southern Tibetan Plateau. The results showed mean summer stream temperature and magnitude of daily thermal variation were lower at all sites when compared with alpine glacierized environments at lower latitudes. Mean stream temperatures for glacier-fed rivers(4.0℃ to 6.5℃)were minimum and least variable near the glacier terminus with increasing toward downstream(+0.13℃ km^(–1) to +0.28℃ km^(–1)). Meanwhile, stream temperature in 2008 was similar to that in 2007 and2009. For the non-glacial rivers, mean stream temperatures was about 9.0℃ with significantly warmer in summer months in 2009 and 2007 than that in 2008. These differences indicated that stream temperature was strongly influenced by discharge and precipitation. Particularly, the glacier mass balance played a large role on the stream temperature directly when the glacier melt contributed more than 50% of the glacial river runoff. Our results demonstrated the stream thermal variability from southern Tibetan rivers and provided new insight into the influence of glacier mass balance on stream thermal variability in high-altitude river system.

G-WADI—the first decade

The G-WADI network by UNESCO promotes the global capacity for management of water resources in arid and semi-arid areas. The primary aim has been to build a comprehensive global network to promote regional and international cooperation so as to in- crease knowledge and improve management practices through the sharing of information. The G-WADI objectives and achieve- ments of the past 10 years are reviewed. A number of key initiatives have been implemented^the formation of five regional net- works, the creation of a central G-WADI web site, promotion of near-real-time rainfall distribution software enhanced by the in- clusion of satellite based precipitation estimations, as well as workshop and web-based activities on chemical and isotopic tracers and on rain water harvesting. Two workshops on surface and on groundwater modeling, supported by publications have been held in India and China. The Asian G-WADI network remains very active, but activities in the other three regions are developing （Af- rica, Arab Region, Latin America and the Caribbean）.

The Debris Flow of 1^stAugust 2012 in Kakpenyi-Tinta (Akwaya Sub Division) Southwest Cameroon—I: Event Description, Causes and Impacts

Compared to large-scale infrequent disasters like volcanic eruptions, earthquakes, and gas explosions from volcanic (maar) lakes, most small-scale everyday disasters (e.g., landslides and floods) are not well reported and documented in Cameroon, despite the fact that cumulatively, they cause the most casualties and distress to the people affected. This paper documents a debris flow that occurred on the 1st of August 2012 in Kakpenyi, a quarter found in Tinta, one of the villages of Akwaya Sub Division in Manyu Division of the Southwest Region of Cameroon. The event started from the western slope (06&#176;14.350'N & 09&#176;31.475'E) of a hogback in the settlement, and mobilized ca 3.47 × 106 m3 of material over a ca 1 km distance. The material was made up of a chaotic mix of mud, rock fragments, boulders, twigs, tree logs, trunks, and roots. Its distal part dammed river Kakpenyi forming a 10 m deep lake which eventually safely emptied itself. No casualties were recorded but 20 people got injured and 21 people lost farmland. The debris flow was not caused by earthquake shaking. Instead, inappropriate land use acted as a remote cause to predispose the steep slope, while heavy rainfall triggered the flow. Verbal reports talk of a similar event 40 years ago in the area. This shows that Kakpenyi is vulnerable to this kind of hazard, requiring that major infrastructural development projects like roads and bridges in the area be preceded by detailed hazard and vulnerability assessments.

Environmental Monitoring Systems: Review and Future Development

Monitoring and recording large time series of data and making them available for studying—are the key roles of environmental monitoring systems. This study produce review of three different measurement monitoring systems (NSUNET, WAHASTRAT and MERIEXWA) with same design, which were placed during different time frame in the Northern Serbia (Vojvodina Province). Each of three monitoring systems has different demands and requirements which were addressed accordingly in their design. Power supply conditions for two systems are primary cells and solar panels, while NSUNET has constant power supply only during nighttime. Data is transmitted in MERIEXWA using binary protocol, WAHASTRAT using http, while NSUNET sends data over ftp. Same topology is used in all systems—each node sends data directly to the central location (in case of NSUNET two locations are provided for backup purposes). NSUNET system sends data using specific structure and stores them as plain text files. It also has different approach for time synchronization and monitoring issues. The main result of this study is to present how to create system that provides good quality and unchanged data from monitoring sensor to the end user while maintaining whole data structure transmission costs low. Furthermore, data collected from NSUNET were used in order to assess the influence of urbanization on regional climate modification, which leads to the creation of urban climate. Propositions for new system development combining best from all three systems are discussed.

Analysis of Climate Variability and Its Influence on the Hydrological Response of the Catchment Area of Kadey (East Cameroon)

Register in the framework of the International Program of Research on Water Resources Management and Protection of Ecosystems, the Congo basin in which lies the catchment area of the Kadey (2647 km2) was selected to better assess the impact climate variability on the water surface in the perspective of supply drinking water both in the rainy season and in periods of low water. Based on new data from rainfall and flow rates obtained in the last fifteen years (1998-2013), the major trends in time series and the scope of the “drought” were identified. The historical rainfall in the basin is characterized by two major ruptures rainfall in 1969 and 1999. These have generated an order deficit of 14% respectively and an excess of nearly 19%. These phenomena also affected the recurrence of cumulative rainfall throughout the Kadey basin. Here, the hydrological response to excess rainfall is over 100%. However, it appears that over the period 1970-2012, the number of years that has undergone a “severe drought” is to play down.

关键发现及科学认识的空白和政策建议

引言 总的来讲，北极地区气候和紫外辐射的变化将会产生深远的影响，其影响主要作用于不同营养级的水生物种，作为水生生物生境的自然环境及其化学性质，对水生生态系统起作用的进程和水生生态系统自身的进程。气候变量，例如气温和降水，与淡水生态系统的交互作用非常复杂，而且这种作用可以通过生态系统以某些不易察觉的方式扩散。系统的复杂性使准确预测气候和紫外辐射变化对淡水系统的影响增加了难度，尤其是那些跳跃式或非线形的临界反应，更难把握。由于缺乏对北极淡水系统与气候及其他环境变量之间的相互影响关系的了解，加上北极地区非常稀少的长期淡水监测站点和综合水文生态研究项目，我们的预测能力受到进一步的限制。

紫外线辐射和污染相关胁迫因子对北极淡水生态系统的影响

气候变化很可能作为一种多重胁迫因子,对水生生态系统造成累积的和/或协同的影响。预测的温度上升以及由此带来的降水季节性特征的改变将会增加污染物流入水生生态系统的量,并且会独自提高水生生物体对污染物暴露和影响的易感性。对生物区系造成的结果在多数情况下是加和的(累积的)或倍增的(协同的),其总的结果必然是污染物负荷加重,生物放大作用(指有毒化学物质在食物链各环节中的毒性渐进)加强。同温层中臭氧和紫外线辐射季节性特征的变化也会对水生生态系统的结构和功能产生累加或协同的影响。与预测的同温层臭氧量减少这一原因相比,冰层覆盖度的降低可能对水下紫外线暴露产生更为重大的影响。紫外线辐射水平的大幅升高会导致对生物体的损伤增强(生物分子学、细胞学和生理学上的损害,以及物种组成的变化),而生物区系分配用于抵抗紫外线伤害的能量和资源也会增加,有可能使营养水平上的生产力降低。通过光化学途径,元素的通量将会增加。

Changes in permafrost and snow cover in the Boreal and Arctic zones(BAZs)and their impacts

1.Introduction Amplified climate warming and wetting have been observed in the Boreal and Arctic zones(BAZs).Due to extensive and persistent warming of the climate and the increasing impacts of human activities,we are seeing degradation of the permafrost and rapid shrinkage of the snow cover in the BAZs.Much attention has been paid to the reconstruction of past permafrost and monitoring,mapping and evaluation of permafrost and snow cover,and the use of models to predict and evaluate future gradual permafrost changes.Little attention,however,has been given to the rapidly changing permafrost and the associated implications.This may have led to an underestimation of the rapid changes in the cryolithozone and their effects on the climate,ecosystems,and hydrology systems and on humans.In particular,natural resources and environmental management in northern countries requires better and more systematic understanding of the history,processes,mechanisms and trends of the northern cryosphere and their environmental and engineering impacts.

Linkage between permafrost distribution and river runoff changes across the Arctic and the Tibetan Plateau

River runoff in the Arctic and the Tibetan Plateau(TP) change significantly in recent decades. However, the mechanisms of the physical processes of permafrost river runoff change remain uncertain across large scale. This study investigated the mainstreams and tributaries of main Arctic and TP rivers dominated by permafrost and assessed the linkage between hydrological regime change and permafrost. The results show that the effects of permafrost on river runoff are highly dependent on the permafrost coverage of a watershed. For the past decades, the majority of the Arctic and TP basins showed increased discharge, while all of the studied basins showed increased baseflow, with faster increasing speed than total discharge.Both total discharge and baseflow annual change rate(ΔQ and ΔBF) increased with permafrost coverage, indicating the increments of streamflow are enhanced with high permafrost coverage. Meanwhile, the annual change of precipitation showed weak connection with total discharge and baseflow change. The high permafrost coverage basins showed high annual maximum/minimum discharge ratio(Qmax/Qmin), while the Qmax/Qminchanged slightly in low permafrost cover basins. Our results highlight the importance of permafrost coverage on streamflow regime change for permafrost basins across the northern hemisphere. Due to these linkage between permafrost extent and runoff regime change and the increasing changes of permafrost, more attention should be paid to the change of hydrological processes in permafrost-underlain basins.

The Changing Cold Regions Network:Observation,diagnosis and prediction of environmental change in the Saskatchewan and Mackenzie River Basins,Canada

Climate change is causing rapid and severe changes to many Earth systems and processes,with widespread cryospheric,ecological,and hydrological impacts globally,and especially in high northern latitudes.This is of major societal concern and there is an urgent need for improved understanding and predictive tools for environmental management.The Changing Cold Regions Network(CCRN)is a Canadian research consortium with a focus to integrate existing and new experimental data with modelling and remote sensing products to understand,diagnose,and predict changing land,water,and climate,and their interactions and feedbacks over the geographic domain of the Mackenzie and Saskatchewan River Basins in Canada.The network operates a set of 14 unique and focused Water,Ecosystem,Cryosphere and Climate(WECC)observatories within this region,which provide opportunities to observe and understand processes and their interaction,as well as develop and test numerical simulation models,and provide validation data for remote sensing products.This paper describes this network and its observational,experimental,and modelling programme.An overview of many of the recent Earth system changes observed across the study region is provided,and some local insights from WECC observatories that may partly explain regional patterns and trends are described.Several of the model products being developed are discussed,and linkages with the local to international user community are reviewed—In particular,the use of WECC data towards model and remote sensing product calibration and validation is highlighted.Some future activities and prospects for the network are also presented at the end of the paper.

Effect of glycerol on densification of agricultural biomass

Experiments were conducted to verify the effect of adding glycerol for pelleting of selected agricultural crop residues,namely,wheat,barley,oat and canola straw.Single pelleting tests were conducted to study the effect of biomass type,hammer mill screen size,and crude glycerol content(co-product of biodiesel industry)on pellet quality(density and durability),ash content and gross heat of combustion.Four types of biomass were ground at three different hammer mill screen sizes of 6.4,3.2 and 1.6 mm.Each biomass was mixed with three levels of glycerol of 2.5%,5.0%and 7.5% by weight.Pellets were made at a pre-set load of 4400 N(138.9 MPa)using single-pelleting unit attached to an Instron testing machine.Quality of pellets was determined by measuring pellet density,relaxed density,durability(measured by pellet drop test)and specific energy required to make a pellet.The gross heat of combustion and ash content of pellets were also determined and compared.The highest pellet density(988-1133 kg/m^(3))and relaxed density(992-1142 kg/m^(3))were obtained from biomass ground using a hammer mill screen size of 6.4 mm.A decrease in hammer mill screen size resulted in reduced durability.The highest durability of biomass obtained from hammer mill screen size of 6.4 mm ranged from 97%-100%.Addition of glycerol resulted in lower ash content in majority of pellets.The highest gross heat of combustion was observed in pellets made from wheat straw with 7.5% glycerol content(38.3 MJ/kg).Addition of glycerol resulted in lower pellet densities,lower ash content,no change in durability and higher gross heating values.