Spatial variability of snowmelt timing from AMSR‐E and SSM/I passive microwave sensors,Pelly River,Yukon Territory,Canada     

Joan M. Ramage  Jeremy D. Apgar  Rose A. McKenney  Wade Hanna 《水文研究》2007,21(12):1548-1560

Spring snow melt run‐off in high latitude and snow‐dominated drainage basins is generally the most significant annual hydrological event. Melt timing, duration, and flow magnitude are highly variable and influence regional climate, geomorphology, and hydrology. Arctic and sub‐arctic regions have sparse long‐term ground observations and these snow‐dominated hydrologic regimes are sensitive to the rapidly warming climate trends that characterize much of the northern latitudes. Passive microwave brightness temperatures are sensitive to changes in the liquid water content of the snow pack and make it possible to detect incipient melt, diurnal melt‐refreeze cycles, and the approximate end of snow cover on the ground over large regions. Special Sensor Microwave Imager (SSM/I) and Advanced Microwave Scanning Radiometer for EOS (AMSR‐E) passive microwave brightness temperatures (T_b) and diurnal amplitude variations (DAV) are used to investigate the spatial variability of snowmelt onset timing (in two stages, ‘DAV onset’ and ‘melt onset’) and duration for a complex sub‐arctic landscape during 2005. The satellites are sensitive to small percentages of liquid water, and therefore represent ‘incipient melt’, a condition somewhat earlier than a traditional definition of a melting snowpack. Incipient melt dates and duration are compared to topography, land cover, and hydrology to investigate the strength and significance of melt timing in heterogeneous landscapes in the Pelly River, a major tributary to the Yukon River. Microwave‐derived melt onset in this region in 2005 occurred from late February to late April. Upland areas melt 1–2 weeks later than lowland areas and have shorter transition periods. Melt timing and duration appear to be influenced by pixel elevation, aspect, and uniformity as well as other factors such as weather and snow mass distribution. The end of the transition season is uniform across sensors and across the basin in spite of a wide variety of pixel characteristics. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Impacts of Climatic Factors on Runoff Coefficients in Source Regions of the Huanghe River   总被引：4，自引：0，他引：4  

CHEN Liqun LIU Changming LI Yanping WANG Guoqiang 《中国地理科学(英文版)》2007,17(1):047-055

Runoff coefficients of the source regions of the Huanghe River in 1956–2000 were analyzed in this paper. In the 1990s runoff of Tangnaihai Hydrologic Station of the Huanghe River experienced a serious decrease, which had at- tracted considerable attention. Climate changes have important impact on the water resources availability. From the view of water cycling, runoff coefficients are important indexes of water resources in a particular catchment. Kalinin baseflow separation technique was improved based on the characteristics of precipitation and streamflow. After the separation of runoff coefficient (R/P), baseflow coefficient (Br/P) and direct runoff coefficient (Dr/P) were estimated. Statistic analyses were applied to assessing the impact of precipitation and temperature on runoff coefficients (including Dr/P, Br/P and R/P). The results show that in the source regions of the Huanghe River, mean annual baseflow coefficient was higher than mean annual direct runoff coefficient. Annual runoff coefficients were in direct proportion to annual pre- cipitation and in inverse proportion to annual mean temperature. The decrease of runoff coefficients in the 1990s was closely related to the decrease in precipitation and increase in temperature in the same period. Over different sub-basins of the source regions of the Huanghe River, runoff coefficients responded differently to precipitation and temperature. In the area above Jimai Hydrologic Station where annual mean temperature is –3.9oC, temperature is the main factor in- fluencing the runoff coefficients. Runoff coefficients were in inverse relation to temperature, and precipitation had nearly no impact on runoff coefficients. In subbasin between Jimai and Maqu Hydrologic Station Dr/P was mainly affected by precipitation while R/P and Br/P were both significantly influenced by precipitation and temperature. In the area be-tween Maqu and Tangnaihai hydrologic stations all the three runoff coefficients increased with the rising of annual precipitation, while direct runoff coefficient was inversely proportional to temperature. In the source regions of the Huanghe River with the increase of average annual temperature, the impacts of temperature on runoff coefficients be-come insignificant.  相似文献   

Coupled surface water–groundwater model and its application in the arid Shiyang River basin,China     

Li‐Tang Hu  Zhong‐Jing Wang  Wei Tian  Jian‐Shi Zhao 《水文研究》2009,23(14):2033-2044

The planning and management of water resources in the Shiyang River basin, China require a tool for assessing the impact of groundwater and stream use on water supply reliabilities and improving many environment‐related problems such as soil desertification induced by recent water‐related human activities. A coupled model, integrating rule‐based lumped surface water model and distributed three‐dimensional groundwater flow model, has been established to investigate surface water and groundwater management scenarios that may be designed to restore the deteriorated ecological environment of the downstream portion of the Shiyang River basin. More than 66% of the water level among 24 observation wells have simulation error less than 1·0 m. The overall trend of the temporal changes of simulated and observed surface runoff at the Caiqi gauging station remains almost the same. The calibration was considered satisfactory. Initial frameworks for water allocation, including agricultural water‐saving projects, water diversion within the basin and inter‐basin water transfer, reducing agricultural irrigation area and surface water use instead of groundwater exploitation at the downstream were figured out that would provide a rational use of water resources throughout the whole basin. Sixteen scenarios were modelled to find out the most appropriate management strategies. The results showed that in the two selected management options, the groundwater budget at the Minqin basin was about 1·4 × 10⁸ m³/a and the ecological environment would be improved significantly, but the deficit existed at the Wuwei basin and the number was about 0·8 × 10⁸ m³/a. Water demand for domestic, industry and urban green area would be met in the next 30 years, but the water shortage for meeting the demand of agricultural water use in the Shiyang River basin was about 2·2 × 10⁸ m³/a. It is suggested that more inter‐basin water transfer should be required to obtain sustainable water resource use in the Shiyang River basin. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

淮河源区中更新世黄土堆积的元素地球化学特征及其古气候意义   总被引：1，自引：1，他引：0  

刘奇  宋传中  崔王  王化可  张妍  王荻  曹宗平 《地球科学与环境学报》2007,29(4):356-361

利用地球化学元素分析方法,对淮河源区中更新世黄土、古土壤剖面含有的化学元素及多种化学元素指标进行了分析。研究表明:区内中更新世以来的气候变化,主要以湿热气候为主,淋溶及氧化作用较强;表现在气温上HT-1~HT-3的气温较低,HT-4~HT-7的气温高,HT-8的气温又相对较低,其变化趋势表现为中更新世经历了从早期寒冷转湿热转温干,中期凉干转暖湿到晚期温湿转暖湿。  相似文献   

Influence of Land Use/Cover Change on Storm Runoff— A Case Study of Xitiaoxi River Basin in Upstream of Taihu Lake Watershed     

WAN Rongrong YANG Guishan 《中国地理科学(英文版)》2007,17(4):349-356

Land use/cover change (LUCC) is one of the main boundary conditions which influence many hydrologic processes. In view of the importance of Taihu Lake Watershed in China and the urgency of discovering the impacts of LUCC on storm runoff, two flood events under five land cover scenarios in the Xitiaoxi River Basin of the upstream of Taihu Lake watershed were simulated by distributed hydrologic modeling system HEC-HMS. The influences of each land cover on storm runoff were discussed. It was concluded that under the same rainstorm the ascending order of runoff coefficient and peak flow produced by the 5 different land covers were woodland, shrub, grassland, arable land, and built-up land; the descending order of swelling time were woodland, shrub, grassland, arable land, and built-up land. Scenario of built-up land was the first to reach peak flow, then arable land, grassland, shrub, and woodland. There were close relationships between the runoff coefficients produced by the 5 different land covers. The degrees of impacts on runoff coefficient of land cover change modes were sorted by descending: woodland to built-up land, shrub to built-up land, grassland to built-up land, arable land to built-up land, woodland to arable land, shrub to arable land, arable land to grassland, shrub to grassland, grassland to arable land, and woodland to shrub. Urbanization will contribute to flood disaster, while forestation will mitigate flood disaster.  相似文献   

Sediment budget of the Napo River,Amazon basin,Ecuador and Peru     

A. Laraque  C. Bernal  L. Bourrel  J. Darrozes  F. Christophoul  E. Armijos  P. Fraizy  R. Pombosa  J. L. Guyot 《水文研究》2009,23(25):3509-3524

The upstream‐downstream sediment budget along the Napo River (100 520 km², 6300 m³ s^?1) was studied in the Andean foothills of Ecuador, at the west of the Amazon basin. A comparative study was made during four hydrological cycles (2001–2005) for three hydrological stations located upstream, and during one hydrological cycle (2004–2005) for the fourth one located near the mouth of the Napo River (region of Iquitos in Peru). This analysis showed an unusual increase in the concentration of suspended sediment recorded for the western part of the Amazon plain. Like the runoff (81 l s^?1 km²), which is a world's maximum, the erosion rate (1160 t km^?2 year^?1, i.e. 47% of total suspended solid (TSS) export at the exit of Ecuador), one of the highest for a floodplain basin is the result of a stepper slope than in the rest of the Andean foothills, where typically sedimentation phenomena are predominant, and can be explained in part by a greater tectonic activity. Similar phenomenes were evidenced in small mountainous rivers in New Guinea (Milliman and Syvitski, 1992; Milliman, 1995). On the headwaters of the Napo River drainage basin, the tectonic uplift causes the Pastaza Megafan's existence. This progressively diverts the course of Napo River towards north and also provokes the remobilization of fine fluvial deposits. Moreover, this geodynamic trend is completed by the impact of volcanic eruption, earthquakes and landslides. The combination of these phenomena, so common in the region, has provided a large sediment transfer, not only at present but also in the past, as can be confirmed by the presence of incised terraces, mainly formed by volcanic materials. Then, these results were compared with a similar study carried out further south in the Madeira basin at the Bolivian foothills. These studies show the spatio‐temporal variability of the relation between sediment transfer and geodynamic processes at the Andean Piedmont. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Extensive genetic divergence among Diptychus maculatus populations in northwest China     

孟玮  杨天燕  海萨  马燕武  蔡林钢  马徐发  高天翔  郭焱 《中国海洋湖沼学报》2015,33(3):577-584

D. maculates is a kind of specialized Schizothoracinae fish has been locally listed as a protected animal in Xinjiang Province,China. Ili River located in north of Tianshan Mountain and Tarim River located in north of Qinghai-Tibetan Plateau were two main distribution areas of this fish. To investigate the genetic diversity and genetic structure of D. maculates,four populations from Tarim River system and two populations from Ili River system were collected in this study. A 570-bp sequence of the control region was obtained for 105 specimens. Twenty-four haplotypes were detected from six populations,only Kunes River population and Kashi River population shared haplotypes with each other. For all the populations examined,the haplotype diversity(h) was 0.904 8±0.012 6,nucleotide diversity(π) was 0.027 9±0.013 9,and the average number of pairwise nucleotide differences(k) was 15.878 3±7.139 1. The analysis of molecular variance(AMOVA) showed that 86.31% of the total genetic variation was apportioned among populations,and the variation within sampled populations was 13.69%. Genetic differences among sampled populations were highly significant. F st statistical test indicated that all populations were significantly divergent from each other(P 0.01). The largest F st value was between Yurungkash River population and Muzat River population,while the smallest F st value was between Kunes River population and Kashi River population. NJ phylogenetic tree of D-loop haplotypes revealed two main clades. The neutrality test and mismatch distribution analysis suggested that the fish had went through a recent population expansion. The uplift of Tianshan Mountain and movement of Qinghai-Tibetan Plateau might contribute to the wide genetic divergence of D. maculates in northwest China.  相似文献   

人类活动对海洋生态系统影响的空间量化评价——以莱州湾海域为例   总被引：2，自引：0，他引：2  

李延峰  宋秀贤  吴在兴  俞志明 《海洋与湖沼》2015,46(1):133-139

本文针对海域管理中难以量化人类活动对海洋生态系统影响的问题,提出人海关系空间量化模型,通过完善概念模型、构建指标体系、确定权重及标准,最终利用作用强度和位置关系量化人类活动对海洋生态系统的影响,数值在0—1之间,等分为四个影响程度,由弱到强依次为微弱、中等、强烈和极强,并将该模型和量化方法应用于莱州湾海域。研究结果表明:整个莱州湾受人类活动的综合影响均值为0.425,处于中等影响程度;其中污水排放、围填海工程及港口航运是对莱州湾生态系统影响比较强烈的人类活动;研究海域中40%受到人类活动的强烈影响,44%为中等影响,16%为微弱影响。空间量化分析显示,人类活动对莱州湾近岸海域的综合影响比邻近外海强烈,其中影响较强烈的区域出现在西南近岸海区,而影响较微弱的海区则为莱州湾北部外海。该方法空间量化结果与莱州湾实际情况相符,说明人海关系空间量化模型适合定量化评估人类活动对该海域生态系统的影响,可为"山东半岛蓝色经济区"海域管理提供技术支持。  相似文献   

南渡江河口洪、枯季节水文泥沙变化特征及台风“海鸥”对入海水沙的影响   总被引：1，自引：0，他引：1  

陈斌  高飞  印萍  刘金庆 《海洋与湖沼》2015,46(6):1279-1291

基于2014年最新的洪、枯季节实测资料,分析了南渡江河口海域水文泥沙的季节性变化特征,借助台风"海鸥"过境期间的河道监测数据,研究了台风天气造成的洪水事件对河流入海水沙通量的影响。研究结果表明:(1)洪、枯季节河口海域的水体层化作用不强,洪季的水温高于枯季,但盐度低于枯季。水温呈现向海递减的趋势,而盐度整体分布较为均匀;(2)河口水体含沙量近岸大于远岸,枯季河口三角洲泥沙向西输运。洪季含沙量明显高于枯季,大量泥沙在台风季节被冲刷入海,而后向海或向西输运扩散;(3)河口海域为不规则全日潮,呈现东西向往复流特征。温度、盐度和浊度均呈现较强的潮汐性变化特征;(4)枯季河道内存在明显的盐水楔,锋面处的垂向梯度很大,在口门向陆大约12—15 km以远的河道水体不再受潮汐影响;(5)台风"海鸥"影响下,南渡江洪峰期间的径流量和含沙量均远远超过多年平均值,反映了南渡江河口地区"台风季节"的特点。  相似文献   

基于氮稳定同位素的九龙江口鱼类营养级研究   总被引：1，自引：1，他引：0  

廖建基  郑新庆  杜建国  陈彬 《海洋学报》2015,37(2):93-103

采用氮稳定同位素技术对2013年6—8月九龙江口采集到的隶属于13目42科61属共71种鱼类的营养级进行研究。结果表明,九龙江口鱼类的δ15 N值跨度较大,介于7.23‰~14.66‰之间。以菲律宾蛤仔(Ruditapes philippinarum)为基准生物估算出鱼类的营养级介于1.70~3.89之间,营养级最低与最高的鱼类分别为少牙斑鲆(Pseudorhombus oligodon)与多鳞鱚(Sillago sihama)。与Fishbase同种鱼类的营养级数据进行比较,83.1%的鱼类的营养级均值处于Fishbase同种鱼类的营养级范围内,但81.7%的鱼类的营养级均值比Fishbase同种鱼类的营养级均值略低;与传统的胃含物分析结果比较,58.3%的鱼类的营养级在0.5个营养级的误差范围内。基于氮稳定同位素估算的鱼类营养级较低的原因可能与本研究样品中低龄鱼及幼鱼比例较大有关。与其他方法相比,稳定同位素法在研究体型较小的幼鱼和低龄鱼营养级更具优势。鱼类营养级随其个体大小的变化明显,但存在种的差异性:不同体长的髭缟鰕虎鱼(Tridentiger barbatus)和绿鳍鱼(Chelidonichthys kumu)的营养级跨度较大,分别为1.54和1.43;而鳓(Ilisha elongata)等的营养级则跨度较小,这可能与不同鱼类的食性变化有关。  相似文献