Monitoring Flood Extent and Forecasting Excess Runoff Risk with RADARSAT-1 Data

Earth observation from active microwave satellites such as RADARSAT-1 is an excellent tool to monitor and forecast floods. Two complementary approaches are described in this paper: (a) real time or near-real time monitoring of flood extent and (b) mapping of hydrological properties of drainage basins. Since it can penetrate through clouds, which usually occur during precipitation periods, and due to the fact that it can be programmed with different incidence angles, RADARSAT-1 enables frequent coverage over specific areas of interest. It has been used successfully to monitor a major flood of the Red River in Manitoba in 1997, by providing frequent coverage of the flood during its progression and decrease. Resulting data and images have been useful in planning the emergency measures and in assessing flood damage. RADARSAT has also the ability to characterize hydrological properties of watersheds. It has been used in agricultural catchments in Europe for mapping soil surface roughness, which affects runoff coefficients, concentration time and resistance to erosion processes. Used to complement optical data, RADARSAT has provided information on the status of land use and soil protective cover in drainage basins. This information can then be translated into parameters and coefficients that hydrological models can use for runoff and flood forecasting     

Land cover changes based on plant successions: Deforestation,rehabilitation and degeneration of forest in the upper Dadu River watershed

The land use/cover classification system is the foundation for land use/cover change study. Remote sensing data were firstly used for land use and land cover classification in the United States in 1971 and the Anderson Classification System was proposed in 1976[1], which was put into use in mapping 1:250000 land use and land cover of the United States. A series of new land cover classification systems have been established in recent years through research projects such as FAO LCCS and Bi…     

SEDIMENT TRANSPORT PROCESSES IN AGRICULTURAL WATERSHEDS

lINTR0DUCTI0NTheerosion,transportanddep0siti0nofsedimentinawatershedarepallofthenaturalsystemofwatershedprocesses.InanundistUrbedwatershed,s0ilsinuplandareasaregraduallyeroded,transportCdforsomedistanceandeventuallydepositedatlowereIevations.WhenwatershedsaredistUrbedbyhumanactivitiessuchasclearingofvegetation,urbaniZati0n,orotherchangesthataffectthelandscaPe,unstablechannelswithlocallyhighratesoferosion,transport,0rdepositionofsedimentoftenaretheresult.Theimpact0fer0sionisespeciallyhigh…     

Cross-Media Models of the Chesapeake Bay Watershed and Airshed

A continuous, deterministic watershed model of the Chesapeake Bay watershed, linked to an atmospheric deposition model is used to examine nutrient loads to the Chesapeake Bay under different management scenarios. The Hydrologic Simulation Program - Fortran, Version 11 simulation code is used at an hourly time-step for ten years of simulation in the watershed. The Regional Acid Deposition Model simulates management options in reducing atmospheric deposition of nitrogen. Nutrient loads are summed over daily periods and used for loading a simulation of the Chesapeake estuary employing the Chesapeake Bay Estuary Model Package. Averaged over the ten-year simulation, loads are compared for scenarios under 1985 conditions, forecasted conditions in the year 2000, and estimated conditions under a limit of technology scenario. Limit of technology loads are a 50%, 64%, and 42% reduction from the 1985 loads in total nitrogen, total phosphorus, and total suspended solids, respectively. Urban loads, which include point source, on-site wastewater disposal systems, combined sewer overflows, and nonpoint source loads have the highest flux of nutrient loads to the Chesapeake, followed by crop land uses.on assignment from NOAA Air Resources Laboratory     

淮南及淮北煤田第四纪“底砾层”成因模式探讨

安徽省淮南与淮北煤田第四纪“底砾层”的研究,对于煤矿提高上限开采具有重要意义。关于底砾层的成因问题,有多种观点。本文分析研究了两淮地区第四纪底砾层沉积面貌、描述了砾石外观形态（如瓜子形、拖鞋状、葫芦状、马鞍状等）及表构特征,包括泥包砾、镶嵌及缝隙结构等,提出两淮地区底砾层为冰碛物（冰种沉积）。地球化学测试及分析结果表明,两淮地区砾石的几种主要化学成分含量非常接近,从而说明两淮底砾层属同一物源。综合这两方面的论证,提出了底砾层的“停积－融坠型冰碛物沉积模式”,并进行了冰碛物的物源方向问题的探讨。     

嫩江下游沼泽湿地变化的驱动力分析

从20世纪80年代中期到20世纪末,嫩江下游地区年平均气温上升、湿润度逐渐下降、降水量减少、年径流减少等原因导致了沼泽湿地面积大量减少。沼泽湿地减少的面积距主要公路和铁路的最短距离成幂指数关系;与主要城市最短距离的e指数关系并不显著。人口增长、农业现代化水平的提高以及人类对眼前利益的追逐是沼泽开垦为耕地的主要社会经济驱动力。     

中国新三大地带宏观区域格局的划分

随着区域经济社会的快速发展, 中国现行三大地带的划分已难以适应新形势下统筹区域发展的要求。在全面介绍了完整的区域经济体系和美国4层次区域经济体系划分的基础上, 按照科学发展观以及“五个统筹”的要求, 提出了未来中国东北及东部沿海、中部及近西部和远西部等新的三大地带和东北、京津冀鲁沿海、沪苏浙沿海、粤闽琼沿海、黄河上中游、长江上中游、珠江上中游、内蒙古、新疆和青藏高原等10大综合经济区的划分方案。     

Global sensitivity analysis of hydrologic processes in major snow‐dominated mountainous river basins in Colorado

The performance of watershed models in simulating stream discharge depends on the adequate representation of important watershed processes. In snow‐dominated systems, snow, surface and subsurface hydrologic processes comprise a complex network of nonlinear interactions that influence the magnitude and timing of discharge. This study aims to identify critical processes and interactions that control discharge hydrographs in five major mountainous snow‐dominated river basins in Colorado, USA. A comprehensive watershed model (Soil and Water Assessment Tool) and a variance‐based global sensitivity analysis technique (Fourier Amplitude Sensitivity Test) were used in conjunction to identify critical models parameters and processes that they represent. Average monthly streamflow and streamflow root mean square error over a period of 20 years were used as two separate objective functions in this analysis. Examination of the sensitivity of monthly streamflow revealed the influence of parameters on flow volume, whereas the sensitivity of streamflow root mean square error also exposed the influence of parameters on the timing of the hydrographs. A stability analysis was performed to investigate the computational requirements for a robust sensitivity analysis. Results show that streamflow volume is mostly influenced by shallow subsurface processes, whereas interactions between groundwater and snow processes were the key in the timing of streamflows. A large majority of important parameters were common among all study watersheds, which underlies the prospect for regionalization of process‐based hydrologic modelling in headwater river basins in Colorado. Copyright © 2013 John Wiley & Sons, Ltd.     

Projected 21st century climate change on snow conditions over Shasta Dam watershed by means of dynamical downscaling

Snow is an important component of the Earth's climate system and is particularly vulnerable to global warming. It has been suggested that warmer temperatures may cause significant declines in snow water content and snow cover duration. In this study, snowfall and snowmelt were projected by means of a regional climate model that was coupled to a physically based snow model over Shasta Dam watershed to assess changes in snow water content and snow cover duration during the 21st century. This physically based snow model requires both physical data and future climate projections. These physical data include topography, soils, vegetation, and land use/land cover, which were collected from associated organizations. The future climate projections were dynamically downscaled by means of the regional climate model under 4 emission scenarios simulated by 2 general circulation models (fifth‐generation of the ECHAM general circulation model and the third‐generation atmospheric general circulation model). The downscaled future projections were bias corrected before projecting snowfall and snowmelt processes over Shasta Dam watershed during 2010–2099. This study's results agree with those of previous studies that projected snow water equivalent is decreasing by 50–80% whereas the fraction of precipitation falling as snowfall is decreasing by 15% to 20%. The obtained projection results show that future snow water content will change in both time and space. Furthermore, the results confirm that physical data such as topography, land cover, and atmospheric–hydrologic data are instrumental in the studies on the impact of climate change on the water resources of a region.     

Confounded by forgotten legacies: Effectively managing watersheds in the contemporary age of unknown unknowns

Contemporary watershed management practices can reflect oversimplifications of relationships between anthropogenic pressures and resource degradation. Remediation and restoration efforts often focus on recent land use practices as the primary driver of hydrologic regime changes. We present a case study that serves as an example to the scientific and watershed management communities of the lasting influences of historic land use practices and natural physical processes on a stream in the central United States listed as impaired by the federal government. Abnormal spatiotemporal streamflow relationships, determined by means of an experimental watershed study, alerted the authors to possible sink/source behavior in the upper‐watershed. Subsequent research uncovered archival evidence of coal mining, which may provide at least partial explanation. Additional investigation identified hydrologic processes associated with natural landscape evolution, noted by early‐20th‐century researchers, which are considered in the context of the current water quality and flow regime. Despite best‐intended management practices, regulatory agencies, scientists, and local decision makers have not accounted for such practices and processes, instead relying on recent development as the proximate cause of designated impairment. We present argumentation that historic land use (coal mining) and landscape processes comprise cumulative yet unconsidered legacy effects that contribute systemically to the observed hydrologic regime of the watershed. Results hold important implications for contemporary watershed management, and support rethinking the case‐by‐case appropriateness of federal and state water impairment listings, and the achievability of restoration efforts in many developing watersheds.