The contribution of aeolian processes to fluvial sediment yield from a desert watershed in the Ordos Plateau,China   总被引：2，自引：0，他引：2       下载免费PDF全文

Wanquan Ta  Haibin Wang  Xiaopeng Jia 《水文研究》2015,29(1):80-89

In arid zones, many active aeolian dunes terminate at ephemeral and perennial desert rivers. The desert rivers show very high rates of sediment transport that cause deleterious downstream effects on the river system and ecology. High sediment loading has been attributed to severe water erosion of sparsely covered watersheds during infrequent but heavy rainfall. Although aeolian erosion is known to lead to high rates of wind‐blown sand transport, direct confirmation of whether the aeolian processes accelerate or inhibit fluvial sediment loss is lacking. Here, we show that an aeolian‐fluvial cycling process is responsible for the high rate of suspended sediment transport in a Sudalaer ephemeral desert channel in the Ordos Plateau of China. Frequent aeolian processes, but low frequency (once every 3 years on average) flooding, occur in this region. Wind‐blown saltating grains appeared to be unable to cross the desert channel because of interruption of channel‐induced recirculating air flow, and therefore tended to settle in the channel during the windy seasons, leading to channel narrowing. During flooding, this narrowed channel was found to yield a threefold increase in suspended sediment loading and a 3.4‐fold increase in the weight percentage of the 0.08–0.2 mm sediment fraction on 18 July 2012. Loss of stored aeolian sand due to channel erosion accounted for about half of the total sediment yield in this watershed. These findings show that aeolian processes play an essential role in accelerating the sediment yield from a watershed characterized by aeolian‐fluvial interplay and also suggest that the drier the region and the greater the aeolian process, the more the aeolian process contributes to fluvial sediment yield. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Impact of model development,calibration and validation decisions on hydrological simulations in West Lake Erie Basin   总被引：1，自引：0，他引：1       下载免费PDF全文

Prasad Daggupati  Haw Yen  Michael J. White  Raghavan Srinivasan  Jeffrey G. Arnold  Conor S. Keitzer  Scott P. Sowa 《水文研究》2015,29(26):5307-5320

Watershed simulation models are used extensively to investigate hydrologic processes, landuse and climate change impacts, pollutant load assessments and best management practices (BMPs). Developing, calibrating and validating these models require a number of critical decisions that will influence the ability of the model to represent real world conditions. Understanding how these decisions influence model performance is crucial, especially when making science‐based policy decisions. This study used the Soil and Water Assessment Tool (SWAT) model in West Lake Erie Basin (WLEB) to examine the influence of several of these decisions on hydrological processes and streamflow simulations. Specifically, this study addressed the following objectives (1) demonstrate the importance of considering intra‐watershed processes during model development, (2) compare and evaluated spatial calibration versus calibration at outlet and (3) evaluate parameter transfers across temporal and spatial scales. A coarser resolution (HUC‐12) model and a finer resolution model (NHDPlus model) were used to support the objectives. Results showed that knowledge of watershed characteristics and intra‐watershed processes are critical to produced accurate and realistic hydrologic simulations. The spatial calibration strategy produced better results compared to outlet calibration strategy and provided more confidence. Transferring parameter values across spatial scales (i.e. from coarser resolution model to finer resolution model) needs additional fine tuning to produce realistic results. Transferring parameters across temporal scales (i.e. from monthly to yearly and daily time‐steps) performed well with a similar spatial resolution model. Furthermore, this study shows that relying solely on quantitative statistics without considering additional information can produce good but unrealistic simulations. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

土地利用空间格局的置换变化与代换变化分析     

冉建波  陈兴伟 《地球信息科学学报》2015,17(6):661-667

为揭示土地利用空间格局的动态变化,本文基于土地利用转移矩阵,从类型间的空间转移过程出发,构建了置换变化与代换变化的计算模型,并对其2种变化进行了分析。置换变化是2种类型之间以相同面积发生空间位置的置换过程,且各种类型的数量结构保持不变;代换变化则是所研究类型的数量结构保持不变,而与之转换的其他类型数量上的增加或减少;从而将单一类型的总变化进一步细分为置换变化、代换变化与净变化。以晋江流域1985年与2006年2期土地利用格局的变化为例进行分析,结果显示：在1985-2006年间,晋江流域的土地利用空间格局发生了显著变化;园地、建设用地、未利用地呈现扩张态势,草地与旱地呈现萎缩变化,水域变化不大;这6种地类的交换变化面积相对较少,以置换变化为主。水田与林地则主要表现为空间位置的交换变化,其中,水田呈现出与林地、旱地2种类型之间的置换变化,而林地则主要是园地-林地与林地-草地这2对类型间的代换变化。结果表明,通过置换变化与代换变化的分析,更细化了各种类型之间的动态变化过程。  相似文献   

基于Pfafstetter规则的流域编码算法并行化方法     

王春  江岭  陈泰生  杨灿灿 《地球信息科学学报》2015,17(5):556-561

流域编码是以子流域划分进行流域相关研究的重要内容。Pfafstetter 流域编码以编码唯一、顾及流域拓扑关系及编码效率高等优点而被广泛采用。本文在流域相关研究的分析范围不断增大、数据精度越来越高的需求背景下,以Pfafstetter 编码为基础,对流域编码并行化方法进行研究。首先,分析了Pfafstetter 编码不全面和码位不一致的问题,改进了Pfafstetter 编码规则;然后,从数据并行的角度,讨论了并行计算环境下的数据划分及并行化策略,进而设计了流域编码并行算法;最后,利用长江中上游流域SRTM数据,在集群系统上对流域编码并行算法的正确性和并行性能进行了测试。实验结果表明,本文设计实现的流域编码并行算法可获取与实际较为一致的计算结果,且提高了编码计算效率,可为基于子流域划分的流域分析并行化提供参考。  相似文献   

面向城市平原地区暴雨积涝汇水区分级划分的方法研究     

薛丰昌  盛洁如  钱洪亮 《地球信息科学学报》2015,17(4):462-468

汇水区划分是分布式水文模型计算的基础。针对现有方法使用DEM在平原城市地区划分的汇水区不符合实际地形情况,本文提出了一种面向城市平原地区分级划分汇水区的技术方法。该方法从城市用地分类角度出发将城市分为中心城区和郊区,依据城市排水主干水系进行汇水区一级划分,将影响中心城区和郊区的不同径流因子分别融入DEM中,利用细化的DEM进行二级汇水区划分;在此基础上,根据实际汇流情况,结合Voronoi图,对中心城区进行三级划分,最后通过GIS技术进行修正。该方法既结合了传统DEM生成子流域的算法,又融入了城市区域地物地貌特点,能更好地满足城市地区的需要。选择上海市嘉定区西北部地区为实验样区,利用该方法进行汇水区划分比较表明,其对于城市平原地区具有很好的适用性。  相似文献   

The place of rural, remote and least-wealthy small islands in international water development: the nexus of geography–technology sustainability in Chuuk State, Federated States of Micronesia     

WILLIAM JAMES SMITH JR 《The Geographical journal》2008,174(3):251-268

Many least-wealthy, rural, remote and resource-poor small island communities are unlikely to benefit from high-profile global water improvement initiatives. Their small landmasses, geologic composition, geography, social and technological isolation, colonial history, and weak educational and financial resources constitute significant barriers to improving access to safe drinking water. This paper discusses the relatively unique position of such island societies in the international community, providing a case study of the Federated States of Micronesia that integrates data and information pertaining to water resources management and governance, spanning from the island village to national scale. A vision is offered regarding the interaction between small island human and biophysical water systems, manifesting ways to pursue water resource development to improve public health which are constructed to be economically, physically and culturally sustainable.  相似文献   

干旱区典型流域近30年土地利用/土地覆被变化的分形特征分析——以玛纳斯河流域为例   总被引：24，自引：2，他引：22  

李义玲  乔木  杨小林  周生斌 《干旱区地理》2008,31(1):75-81

利用1976、1989、2005年三期遥感影像,运用GIS和分形理论研究干旱区典型流域——玛纳斯河流域近30年的土地利用/土地覆被变化的复杂性和稳定性。结果表明:玛纳斯河流域各时段的土地利用/土地覆被类型分布具有分形结构,土地利用/土地覆被类型形状复杂性和斑块的稳定性波动变化,1976、1989、2005年三时期的各种土地利用/土地覆被类型总平均分维值分别为1.394 0、1.363 4和1.389 9。总平均稳定性指数分别为0.606 0、0.636 6、0.610 1。三期土地利用/覆被类型平均稳定性排序为:沙地>未利用土地>居民点工矿用地>水域>林地>草地>耕地>盐碱地。耕地、林地、草地、盐碱地稳定性相对较差。通过对流域土地利用/土地覆被类型变化复杂性和稳定性的研究,可以为政府协调水土开发和调整土地利用结构提供支持。  相似文献   

滇池流域非点源污染研究进展   总被引：2，自引：0，他引：2  

冯庆  王晓燕 《云南地理环境研究》2008,20(1):41-44

非点源污染是滇池污染治理与控制的重点和难点,自20世纪80年代以来已有大量的研究。这些研究主要涉及了污染物来源及污染负荷估算、不同土地利用方式的污染物流失规律、污染控制方法及治理措施研究等内容、采用了实地考察、调查与监测、试验及模型模拟、3S及计算机技术等研究方法与研究手段。今后,还应在非农业生产所致的非点源污染、完整的监测系统及集成化非点源污染模型建立、水污染总量控制管理以及政策引导、环境保护的监管与实施等方面加强研究工作。  相似文献   

A new approach for linking event‐based upland sediment sources to downstream suspended sediment transport     

Peng Gao  James Puckett 《地球表面变化过程与地形》2012,37(2):169-179

In this study, we proposed a new approach for linking event sediment sources to downstream sediment transport in a watershed in central New York. This approach is based on a new concept of spatial scale, sub‐watershed area (SWA), defined as a sub‐watershed within which all eroded soils are transported out without deposition during a hydrological event. Using (rainfall) event data collected between July and November, 2007 from several SWAs of the studied watershed, we developed an empirical equation that has one independent variable, mean SWA slope. This equation was then used to determine event‐averaged unit soil erosion rate, Q_S/A, (in kg/km²/hr) for all SWAs in the studied watershed and calculate event‐averaged gross erosion E_ea (in kg/hr). The event gross erosion E_t (in kilograms) was subsequently computed as the product of E_ea and the mean event duration, T (in hours) determined using event hydrographs at the outlet of the studied watershed. Next, we developed two linear sediment rating curves (SRCs) for small and big events based on the event data obtained at the watershed outlet. These SRCs, together with T, allowed us to determine event sediment yield SY_e (in kilograms) for all events during the study period. By comparing E_t with SY_e, developing empirical equations (i) between E_t and SY_e and (ii) for event sediment delivery ratio, respectively, we revealed the event dynamic processes connecting sediment sources and downstream sediment transport. During small events, sediment transport in streams was at capacity and dominated by the deposition process, whereas during big events, it was below capacity and controlled by the erosion process. The key of applying this approach to other watersheds is establishing their empirical equations for Q_S/A and appropriately determining their numbers of SWAs. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

不同降雨条件下黄土高原浅层滑坡危险性预测评价   总被引：4，自引：0，他引：4  

庄建琦  彭建兵  张利勇 《吉林大学学报(地球科学版)》2013,43(3):867-876

黄土地区浅层滑坡发育非常广泛,由于其具有分布规律性差、前期变形迹象小、分布范围大、面小点多等特征,目前还无法进行有效预测,因此给黄土地区工程安全带来严重威胁。根据无限边坡模型,结合降雨入渗-土体强度衰减规律和GIS（地理信息系统）技术,构建了不同降雨条件下黄土地区浅层滑坡发育危险性评价模型,并将该评价模型应用到延河一级支流幸福川流域,预测在有效降雨量30、50、100、200 mm条件下,该流域浅层滑坡发育程度,并与当前较为流行的SINMAP模型(地形稳定性模型)进行对比。结果表明：①不稳定和潜在不稳定浅层滑坡主要分布在末级河流的两侧和源头,稳定和较稳定区域主要分布在一级河流河道两侧和塬面上;通过对比分析,SINMAP模型计算的结果与本文建立的模型在降雨强度30 mm时的计算结果较为一致。②在本文建立的模型评价结果中,随着有效降雨量的增加,F_s（稳定性系数）<1.00的不稳定区域所占比例逐渐增加,从30 mm的1.12%到200 mm的4.79%;相反,稳定区域则出现逐渐减少的趋势。③根据已发生灾害点的分布,随着有效降雨量的增加,研究区域已发生的灾害点分布在F_s<1.25的比例明显增加,从30 mm的62%到200 mm的88%,在SINMAP评价模型中,研究区域已发生的灾害点的64%分布在不稳定和潜在不稳定区域内,说明本文所建立的评价模型具有一定的精度。通过与SINMAP评价模型对比,本文建立的模型主要采用基于降雨入渗规律,而SINMAP评价模型主要基于降雨汇流过程,因此在利用过程中应根据区域特征选择利用。  相似文献