Research on Drainage Network Extraction in Liaohe Basin Based on SRTM DEM and ASTER GDEM

In this study,SRTM DEM data and ASTER GDEM data were used as the basic topographic data,and Arc Hydro Tools was utilized for extension module so as to study on extracting digital drainage network of watershed based on surface runoff model,as well as to compare the two extracted results.The result showed that through the introduction of drainage density parameter to determine the river drainage area threshold,the both extracted drainages showed the goodness-of-fit with the factual drainage network on 1∶250 000 scale topographic map,and the extracted digital river could be used in practical operation of the risk assessment model of mountain torrents disaster in Liaohe basin.

Study on Spatial and Temporal Distribution Characteristics of Wind Energy Resource and Preservation in Central and West Hexi Corridor

[Objective] The aim was to explore the spatial and temporal distribution characteristics of wind energy resource and preservation in central and west area of Hexi Corridor. [Method] By dint of the wind speed data from 1955 to 2007 in ten meteorological observation station in central and west area of Hexi Corridor,and special wind tower fine data from January to December in 2007,the distribution and reserves of the region＇s wind energy resources were studied. [Result] The results showed that environmental wind speed was relatively stable in central and west Hexi Corridor. There were no distinct changes in climate characteristics distribution. There were regional differences in the distribution of wind energy,and there was a large numerical area of wind energy in Gazhou County and Yumen City; Wind energy in the region generally was higher. The wind energy density was above 100 w/m2 in the 10 m layer,around 140 w/m2 in most places,and was more than 200 w/m2 in the large number area. The wind grew in vertical direction along with the linear growth of height. Each 10 m high wind increased to 15 w/m2 averagely,50m layer wind energy was greater than the general 240 w/m2 and there were obvious changes on daily and annual with wind energy in central and west area of Hexi Corridor. The duration from March to May was a wind energy-intensive stage,10m height from the ground in the wind around 10：00 in low-value. After growing from 11：00,it met the day largest number at 18：00,and then reduced gradually. Effective wind speed hours in the region in general were more than 6 200 h,and the value in the large areas was close to 7 600 h. [Conclusion] The study laid basis for the development and application of wind energy in central and west area of Hexi Corridor.

How Waterways, Glacial Melt Waters, and Earthquakes Re-aligned Ancient Rivers and Changed Illinois Borders

The borders of Illinois were established when Illinois became a state in 1818. The western border was delineated using the Mississippi River, and the Ohio River was used as the southern border. The eastern border was formed by the Ohio and Wabash Rivers plus the line along latitude 42030＇30＇＇ connecting the Wabash River to Lake Michigan. As initially proposed, the northern border of Illinois would have been 82 km （51 mi） to the south of the current longitude line of 87~31 ＇. This 2,160,000 ha （5,440,000 ac） addition to Illinois resulted in the territory having the required minimum of 40,000 people to qualify as a state. The northern border was moved to allow the linkage of the Great Lakes shipping route to the Illinois and Mississippi River navigation channels. Illinois thus gained a valuable shoreline on Lake Michigan and a location for a shipping port hub which became Chicago. Initially the transfer of goods between these waterways required a portage, but later a shipping canal was created to link the waterways. During the Civil War, Union forces used the connected waterway systems as a northern supply route to avoid the contested Ohio River.

Soil and Crop Damages as a Result of Levee Breaches on Ohio and Mississippi Rivers

Whenever levees on the Ohio or Mississippi rivers are breached, there are soil damages in the flooded areas that impact agricultural management capacities and crop productivity. Floodwaters coat the entire flooded land surface with sediments which include a variety of pollutants, nutrients and contaminants. The nature of the sediments in floodwaters varies with the topographical and land use characteristics of the watershed. The soil types, hydro-geologic features, volume of flow, time of year, agricultural use of fertilizers, pesticides, and other chemicals as well as upstream point sources such as sewage treatment plants, storm sewer drainage and other urban land uses will affect the extent of the contamination and fine scale remediation needed. Preliminary characterization and measurement of soils and sediment deposit at three locations that experienced recent natural and man induced levee breaches are analyzed to identify patterns of soil and crop damage. These findings provide guidance to the restoration of craters, gullies, land scoured areas and contaminated sediment depositional sites with a goal to improve decision-making, risk analysis and remedial effectiveness. Recommendations include： （1） improve characterization and measurement of eroded soils and distribution of sediment contaminants after levee breaching; （2） assess contamination effects on soil productivity and long term agricultural production in order to understand the impacts of flooding on agricultural soils; （3） evaluate reconstruction investments needed to repair levees based on return of the land to productivity and increased landscape resilience by reducing vulnerability to future flooding and levee breaching stress.

Assessment of dam impacts on river flow regimes and water quality:a case study of the Huai River Basin in P.R.China

The Huai River Basin is a unique area in P.R.China with the highest densities of population and water projects.It is also subject to the most serious water pollution.We proposed a distributional SWAT(Soil and Water Assessment Tool) model coupled with a water quality-quantity balance model to evaluate dam impacts on river flow regimes and water quality in the middle and upper reaches of the Huai River Basin.We calibrated and validated the SWAT model with data from 29 selected cross-sections in four typical years(1971,1981,1991 and 1999) and used scenario analysis to compensate for the unavailability of historical data regarding uninterrupted river flows before dam and floodgate construction,a problem of prediction for ungauged basins.The results indicate that dam and floodgate operations tended to reduce runoff,decrease peak value and shift peaking time.The contribution of water projects to river water quality deterioration in the concerned river system was between 0 to 40%,while pollutant discharge contributed to 60% to 100% of the water pollution.Pollution control should therefore be the key to the water quality rehabilitation in the Huai River Basin.

Landform Instability and Land-use Dynamics in Tropical High Mountains, Central Mexico

This investigation is an analysis of the influence of landform instability on the distribution of land-use dynamics in a hydrographical basin, located in the Mexican Volcanic Belt mountain range (central Mexico), currently affected by substantial changes in land use and deforestation. A landform map was produced, in addition to seven attribute maps - altimetry, drainage density, slope, relief energy, potential erosion, geology and tectonics - which were considered as factors for determining landform instability through Multi-criteria Evaluation Analysis. Likewise, the direction and rhythm of land-use dynamics were analyzed in four dates - between 1976 and 2000 - and cross tabulations were made between them, in order to analyze the trends and processes of land-use dynamics. Afterwards, the databases obtained were cross tabulated with the landform variables to derive areas, percentages and correlation indices. In the study area, high-instability landforms are associated with most ancient volcanic and sedimentary landforms, where high altitude, drainage density, slope and potential to develop gravitational and fluvial processes are the major factors favouring a land-use pattern, dominated by the conservation of extensive forest land, abandonment of human land use and regeneration of disturbed areas. In contrast, low-instability landforms correspond to alluvial plains and lava hills covered by pyroclasts, where low potential erosion to develop fluvial processes, added to water and soil availability and accessibility, have favoured a land-use pattern dominated by the expansion of agroforestry plantations and human settlements, showing a marked trend towards either intensification or permanence of the current land use and with little abandonment and regeneration.

On Huck＇s Establishment of Identity in The Adventure of Huckleberry Finn from the Perspective of Initiation Theme

The Adventure of Huckleberry Finn written by Mark Twain is considered as representative novel with initiation theme in American literary circle. It has taken the fancy of the readers throughout the whole world since it was frequently printed and widely translated. In the story, Mark created an image of a boy named Huck who had an unexpected adventure by sailing a raft down the Mississippi River with his friend, Jim. After experiencing the adventure, Huck finally became mature. The present paper gives a brief introduction of the story. Then, the paper mainly explores how Huck established his identity from the following aspects： his disapproval to slavery and his consciousness of moral development and obligation.

Soil Organic Carbon Density in Hebei Province, China: Estimates and Uncertainty

In order to improve the precision of soil organic carbon (SOC) estimates, the sources of uncertainty in soil organic carbon density (SOCD) estimates and SOC stocks were examined using 363 soil profiles in Hebei Province, China, with three methods: the soil profile statistics (SPS), GIS-based soil type (GST), and kriging interpolation (KI). The GST method, utilizing both pedological professional knowledge and GIS technology, was considered the most accurate method of the three estimations, with SOCD estimates for SPS 10% lower and KI 10% higher. The SOCD range for GST was 84% wider than KI as KI smoothing effect narrowed the SOCD range. Nevertheless, the coefficient of variation for SOCD with KI (41.7%) was less than GST and SPS. Comparing SOCD’s lower estimates for SPS versus GST, the major sources of uncertainty were the conflicting area of proportional relations. Meanwhile, the fewer number of soil profiles and the necessity of using the smoothing effect with KI were its sources of uncertainty. Moreover, for local detailed variations of SOCD, GST was more advantageous in reflecting the distribution pattern than KI.

Determining Critical Support Discharge of a Riverhead and River Network Analysis： Case Studies of Lhasa River and Nyangqu River

A riverhead is the demarcation point of continuous water channel and seasonal channel, which is characterized by a criti- cal flow that can support a continuous water body. In this study, the critical support discharge （CSD） is defined as the critical steady flows required to form the origin of a stream. The CSD is used as the criterion to determine the beginning of the riverhead, which can be controlled by hydro-climate factors （e.g., annual precipitation, annual evaporation, or minimum stream flow in arid season）. The CSD has a close correlation with the critical support/source area （CSA） that largely affects the density of the river network and the division of sub-watersheds. In general, river density may vary with regional meteorological and hydrological conditions that have to be considered in the analysis. In this paper, a new model referring to the relationship of CSA and CSD is proposed, which is based on the physical mechanism for the origin of riverheads. The feasibility of the model was verified using two watersheds （Duilongqu Basin of the Lhasa River and Beishuiqu Basin of the Nyangqu River） in Tibet Autonomous Region to calculate the CSA and extract river networks. A series of CSAs based on different CSDs in derived equation were tested by comparing the extracted river networks with the reference network obtained from a digitized map of river network at large scales. Comparison results of river networks derived from digital elevation model with real ones indicate that the CSD （equal to criterion of flow quantity （Qc）） are 0.0028 m3/s in Duilongqu and 0.0085 m3/s in Beishuiqu. Results show that the Qc can vary with hydro-climate conditions. The Qc is high in humid region and low in arid region, and the optimal Qo of 0.0085 m3/s in Beishuiqu Basin （humid region） is higher than 0.0028 m3/s in Duilongqu Basin （semi-arid region）. The suggested method provides a new application approach that can be used to determine the Qo of a riverhead in complex geographical regions, which can also reflect the effect of hydro-climate change on rivers supply in different regions.

Responses of Hyalella Azteca to Chronic Exposure of Mississippi Delta Sediments

Hyalella azteca was used to assess biological impairment in sediments from nine water bodies in the Mississippi Delta （i.e., lower Mississippi alluvial plain）. Water bodies were categorized according to land use and implementation of agricultural best management practices （BMPs）. Sediment samples were collected at three sites within each water body from June to July 2004 and analyzed for 17 current and historic-use pesticides and metabolites. Twenty-eight day H. azteca survival and growth were measured to assess the degree of biological impairment. No significant （P 〉 0.05） mortality occurred in animals exposed to sediments. Significant growth impairment was observed in sediments from all three 303（d） listed water bodies and two of three BMP oxbow lakes. Historic-use pesticides and metabolites were implicated in two of five biologically impaired water bodies. Complex contaminant mixtures often limit attempts to provide clear, definitive sources of biological impairment. In this study, even accounting for sediment characteristics such as sand-silt-clay fractions and organic carbon content did not further clarify sources of toxicity in some water bodies. Finally, results show that implementation of BMPs can mitigate biological impairment within lake sediments.

Application of High-Density Seismic Image in Nondestructive Exploration of Cut-off Cement-Soil Wall in Earth Dam

In order to quickly explore the quality of cut-off wall in dams, a new method of high-density seismic image was adopted and estimated by model and in-situ wall tests.The vibration exciter was employed and several parameters such as hypocentral distance, length of signal record and sampling space in signal collection were determined, which are 8 m, 0.25 ms and 128 ms respectively. Through time and frequency field signal analyses, it is concluded that, the smaller arrival times of reflected longitudinal and surface waves, and the higher their main frequencies, the higher the strength of the wall, vice versa. Accordingly the construction quality of the wall can be evaluated quickly by high-density seismic image.

Typhoon-dominated Influence on Wood Debris Distribution and Transportation in a High Gradient Headwater Catchment

Wood debris is an important component of mountain streams. It causes serious damage and renders difficulty of water resource management in Taiwan. In this study, the quantity of wood debris and variation of migratory wood debris during flood events were examined. The downstream of Gaoshan Creek and Qijiawan Creek, located at Central Taiwan, was selected as the study area. The distribution and dynamic of wood debris in a high gradient headwater catchment were quantified using field surveys. A formula of critical depth for wood debris entrainment was used to evaluate the wood debris migration during three flooding events. In the study area, wood abundance and unit volume increased downstream, and wood density decreased downstream within a channel network. The channel morphology, riparian vegetation, and wood debris characteristics were found to influence the wood storage. As a result, the wood debris has an irregular accumulative distribution in the steep stream, and it migrates easily in the stream because of a high flow discharge. Strong relationships between the channel width and wood debris variables are discovered. Moreover, wood debris has a tendency to accumulate at sites with low stream power and wood debris dams, topographical notches, and unique geological structures. Our findings assist in the understanding of the effects of channel characteristics on distributions of wood debris in steep stream systems.

Influence of Climatic Factors on the Recent Spread of Dubas Bug Ommatissus lybicus （Debergevin） on Date Palm Trees in Some Upper Euphrates Regions of AI-Anbar Province

The dubas bug Ommatissus lybicus （Debergevin） （Homoptera： Tropiduchidae） was almost absent in AI-Anbar Province during the past years, however, field survey conducted in different regions of the province during fall of 2007 indicated the presence of heavy infestation by this pest on date palm trees in some orchards toward the east of Hit city. Infestation was highly influencing in term of affected trees and accumulation of honey dew. Scattered infestations were also recorded in some orchards west of Hit city and near the cities of Haditha, Rawa and AI-Kaim near the Syrian border. However, a sharp decline of dubas population was observed during 2008 and subsequent years as a result of the influence of sever winter in 2008 and the continuous occurrence of dust storms which showed a detrimental effect on moving stages of dubas bug. Data showed that nymphs density reached to about 50 individuals/leaflet recorded during the last week of April and early May of 2008 and was reduced to less than 5 nymphs/leaflet by the end of the third week of May of the same year as a result of the indicated climatic factors. Farther samplings conducted in Spring and Fall seasons of 2009 and 2010 indicated that insects were mainly found on offshoots near the ground with a maximum density reached to 12 individuals/tree. Since the spread of the pest occurred in a discontinuous manner with no correlation to infestations in close by provinces indicating that the arrival or transportation of the pest was happened in a way other than the normal distribution, therefore, dubas bug may not persist in date palm orchards in A1- Anbar Province.

评凯特·格伦维尔的新历史小说

当代澳大利亚著名作家凯特·格伦维尔的两部新历史小说《密河》和《少尉》同以殖民时代的民族接触为题材,出版以来受到国内外文学批评界和史学界的高度关注。小说家声称自己试图通过小说还原澳大利亚的一段历史,但是两部小说在叙事安排上暴露了作者鲜明的文化立场,本文立足批判型解读立场,对两部作品中暗含的意识形态进行揭示,论文提出,《密河》和《少尉》在呈现内容和叙述视角安排上都与小说还原历史真相的创作初衷不符,从表面上看,两部小说反映了小说家渴望民族"和解"的诉求,但小说字里行间通篇都在呼唤对曾经的殖民参与者给予一种超越历史的理解,在这种理解的背后,小说家不仅失落了对于历史的尊重,展现在读者面前的更是一种敬畏白人殖民者的"祖先游戏"。

Rapid climate change-induced collapse of hunter-gatherer societies in the lower Mississippi River valley between ca. 3300 and 2780 cal yr BP

Hunter-gatherer communities in the American Southeast reached an apogee of social and political complexity in the period between ca. 4200 and 3000 cal yr BP. In the lower Mississippi Valley(LMV) the Poverty Point culture defined this period of socio-political elaboration. However, following a significant period of climate change that led to exceptional flooding and a major reorganization of the course of the Mississippi River, this culture collapsed beginning ca. 3300–3200 cal yr BP and the LMV was abandoned for the subsequent 500 years. In this study, we use data from the Jaketown site in the Yazoo Basin of west-central Mississippi to refine the chronology of the climate event that caused the collapse of the Poverty Point culture. A large flood buried Poverty Point-era occupation deposits at Jaketown around 3310 cal yr BP. Lateral migration of the Mississippi River during flooding led to inundation of the Yazoo Basin and re-occupation of ancient river courses. A coarse sand stratum topped by a more than a meter-thick fining upward sediment package marks a crevasse deposit caused by a rupture of the natural levee at Jaketown. This levee breach was part of a larger pattern of erratic flooding throughout the LMV and is associated with major landscape evolution and the abandonment of Poverty Point sites within the valley. Early Woodland peoples re-colonized the crevasse surface after ca. 2780 cal yr BP. Following this event, the Jaketown site and the eastern Yazoo Basin witnessed a period of landscape stability that lasts to this day. These archaeological data demonstrate how climate change and natural disasters can lead to socio-political dissolution and reorganization even in relatively small-scale hunter-gatherer populations.

A systematic analysis of good matching sites between two lattices

The geometrical matching/mismatching of lattices overlapped in 1, 2 and 3 dimensions have been analyzed systematically by variation of lattice misfit in a large range, far beyond the limits for semicoherent interfaces. In order to evaluate the degree of matching, the density of good matching site （GMS） between two lattices is calculated. The analysis shows that the GMS density remains approximately constant, irrespectively to the degree of lattice misfit. This constant, defined as the average GMS density, decreases exponentially with the increasing dimension of misfit. Typically, for 6 = 15%, the average GMS densities are approximately 30%, 7%, and 1.4% for 1D, 2D, and 3D lattice misfits, respectively. The GMS density deviates significantly if a CSL of small X can be defined. The relationship between the GMS distribution and O-lattice is investigated. It indicates that an abrupt increase in the GMS density in an interface parallel to a principal O-lattice plane is equivalent to a reduction of dimension of misfit. This shows the agreement between the selections of principal O-lattice planes as candidates of the preferred interfaces and the condition that interfaces with high GMS density are preferred.

Flood routing model incorporating intensive streambed infiltration

Flood routing models are critical to flood forecasting and confluence calculations. In the streams that dry up and disconnect from groundwater, the streambed infiltration is intensive and has a significant effect on flood wave movement. Streambed infiltration should be considered in flood routing. A flood routing model incorporating intensive streambed infiltration is proposed. In the model a streambed infiltration simulation method based on soil infiltration theory is developed. In this method the Horton equation is used to calculate infiltration capacity. A trial-and-error method is developed to calculate infiltration rate and determine whether the flood wave can travel downstream. A formula is derived to calculate infiltration flow per unit length. The Muskingum-Cunge method with streambed infiltration flow as lateral outflow is used for flood routing. The proposed model is applied to the stream from the downstream of the Yuecheng Reservoir to the Caixiaozhuang Hydrometric Station in the Zhangwei River of the Haihe River Basin. Simulation results show that the accuracy of the model is high, and the infiltration simulation method can represent infiltration processes well. The proposed model is simple and practical for flood simulation and forecasting, and can be used in river confluence calculations in a rainfall-runoff model for arid and semiarid regions.

Vegetable Production After Flooded Rice Improves Soil Properties in the Red River Delta, Vietnam

Vegetable production in South East Asia often is in rotation with flooded rice. The puddling of the soil with flooded rice production may result in unfavourable soil conditions for the subsequent production of dry land crops. To establish whether permanent vegetable production results in favourable soil conditions for vegetables, the effects of five different permanent vegetable production systems and a system of vegetable production in rotation with flooded rice on soil properties after flooded rice were studied in a 2-year field experiment. Bulk density at 0.05–0.10 m depth layer decreased with permanent vegetable production and vegetable production in rotation with flooded rice. The decrease in bulk density was influenced by the application of organic manure and rice husks, and especially by the number of crops cultivated, suggesting that frequency of soil tillage had a major effect on bulk density. Ploughing with buffalo traction after flooded rice, in combination with construction of raised beds, could reduce or totally eliminate negative effects of puddling on soil structure. Bulk density at 0.15–0.20 m soil depth was not influenced. Soil acidity decreased significantly in all systems. Soil organic carbon increased in all systems, but significant increase was only found in two permanent vegetable production systems. Available phosphorus(P) significantly increased in two permanent vegetable production systems, with a positively correlation to the amount of P applied. The significant decrease in bulk density and increase in p H(H2O), after only 2 years, showed that soil conditions after flooded rice could be improved in a short time under intensive vegetable production.