STRUCTURE AND COMPOSITION OF A WATERSHED-SCALE SEDIMENT INFORMATION NETWORK

A "Watershed-Scale Sediment Information Network" (WaSSIN), designed to complement UNESCO’s International Sedimentation Initiative, was endorsed as an initial project by the World Association for Sedimentation and Erosion Research. WaSSIN is to address global fluvial-sediment information needs through a network approach based on consistent protocols for the collection, analysis, and storage of fluvial-sediment and ancillary information at smaller spatial scales than those of the International Sedimentation Initiative. As a second step of implementation, it is proposed herein that the WaSSIN have a general structure of two components, (1) monitoring and data acquisition and (2) research. Monitoring is to be conducted in small watersheds, each of which has an established database for discharge of water and suspended sediment and possibly for bed load, bed material, and bed topography. Ideally, documented protocols have been used for collecting, analyzing, storing, and sharing the derivative data. The research component is to continue the collection and interpretation of data, to compare those data among candidate watersheds, and to determine gradients of fluxes and processes among the selected watersheds. To define gradients and evaluate processes, the initial watersheds will have several common attributes. Watersheds of the first group will be: (1) six to ten in number, (2) less than 1000 km2 in area, (3) generally in mid-latitudes of continents, and (4) of semiarid climate. Potential candidate watersheds presently include the Weany Creek Basin, northeastern Australia, the Zhi Fanggou catchment, northern China, the Eshtemoa Watershed, southern Israel, the Metsemotlhaba River Basin, Botswana, the Aiuaba Experimental Basin, Brazil, and the Walnut Gulch Experimental Watershed, southwestern United States.     

Organochlorine Pesticide Residues in Soils and Sediments of the Herbert and Burdekin River Regions, North Queensland – Implications for Contamination of the Great Barrier Reef

Organochlorine pesticides were widely used in the Australian sugarcane industry from the early 1950s until the late 1980s. Erosion of sugarcane soils and subsequent transport of sediment bound contaminants in river run-off to the Great Barrier Reef lagoon is a growing concern as the cane industry continues to expand. Organochlorine pesticide residues can be used as tracers to examine the worst-case scenario of the spatial extent to which currently used, though less persistent, organic agricultural pesticides might extend. The coastal alluvial flood-plains of the Herbert and Burdekin Rivers in North Queensland have sugarcane growing as the major coastal land-use. Sediment cores and surface sediment samples were collected from near-shore coastal regions of the Herbert and Burdekin Rivers. In addition, soil samples from cane-fields in the two catchments were collected. Analyses of the marine surface sediment samples and three sediment cores revealed the absence of detectable concentrations of organochlorine pesticides (<5 pg/g). However, easily detectable concentrations were found in the sugarcane soil samples (0.01–45 ng/g).     

Dredging influenced sediment toxicity of endosulfan and lindane on black tiger shrimp （Penaeus monodon Fabricius） in Chantaburi River estuary in Thailand

Series of experiments, including background sediment elutriate, spiked-sediment elutriate and spiked- water toxicity tests, were carried out to study the effect of dredging on survivability and ecological competence of commercially important shrimp postlarvae of Penaeus monodon Fabricius. The test sediment represented the most contaminated from endosulfan and lindane in the Chantaburi river mouth estuary. The maximum sediment contamination levels were 49.4 μg/kg of endosulfan and 58.1 μg/kg of lindane in dry weight basis. Dose-response studies in static, non-renewal spiked-sediment elutriate toxicity tests revealed that LC 50 （96 h） values for survival effect based on measured concentrations were 0.50 （0.26-0.95） μg/L for endosulfan and 0.92 （0.63-1.34） μg/L for lindane. The LOECs for endosulfan and lindane were 0.141 and 0.429 μg/L, respectively. The NOECs were estimated to be the dissoluted endosulfan and lindane concentrations from the Chantaburi estuary sediment. The effects on phenoloxidase enzyme activity in shrimp postlarvae exposed for sub-lethal to lethal doses in sediment elutriate were not significant （p〉0.05） at all tested dose levels. The worst case dissolution concentrations of endosulfan and lindane in the water column upon simulatory dredging in the Chantaburi estuary were found to be toxic to shrimp postlarvae on lethal and sub-lethal effects. The NOECs of respective chemicals （i.e., 0.034 and 0.16 μg/L） shared the same orders of magnitude for corresponding NOECs established for whole salt water aquatic life by the USEPA and ＂safe＂ levels calculated by 0.01 safety factor approach. In addition, the significance of multiple pollutant assessments for ecological toxicity testing is highlighted.     

基于择优的块体模型解算南北地震带中南段主要断层滑动速率

In this paper, using the 1999 ~ 2007 GPS velocity field data, and by choosing the optimal block model, we obtained the deformation models applicable to the boundary zones of major blocks and the slip rates of block boundary faults on the mid-southern segment of the North-South Seismic Belt. The results show that： on the Longmenshan fault zone, the tensional and compressive slip rate is small on the Baoxing-Wenchuan segment, about 0. 5 ~ 1.8mm·a^-1, and the rate is relatively significant on the segment of the Wenchuan--Maoxian, as 1.8 ~3.8mm·a^-1; on the Xianshuihe fault belt, there is a certain difference in spatial distribution between the tensional slip rag.e and strike-slip rate： the tensional slip rate （ 8. lmm~a-1） is bigger than the sinistral strike-slip rate （ 4.8mm·a^-1） at the north of the Luhuo region; the tension and compression slip rate is basically the same as the strike-slip rate at Luhuo-Dawu; the Dawu-Kangding section presents a trend of decreased strike-slip rate and increased tensional slip rate; the Kangding-ghimian segment shows a strike-slip nature; the strike-slip rate is significantly greater than the tension/compression rate on the Xiaojiang fault zone; the slip rate on the Red River fault zone shows obvious spatial segmentation, the slip rate is smaller in its northwest part, but with a certain amount of tensional/compression component, 4. 7mm·a^-1 on the Jingdong segment. The segment east of Jingdong （ western Gejiu） is mainly of strike-slip, with a slip rate of 4. 5mm·a^-1.     

：~orous-grain-upper-boundary model and its application to Tarim Basin carbonates

Most of the carbonates in the Tarim Basin in northwest China are low-porosity and low-permeability rocks. Owing to the complexity of porosity in carbonates, conventional rock- physics models do not describe the relation between velocity and porosity for the Tarim Basin carbonates well. We propose the porous-grain-upper-boundary （PGU） model for estimating the relation between velocity and porosity for low-porosity carbonates. In this model, the carbonate sediments are treated as packed media of porous elastic grains, and the carbonate pores are divided into isolated and connected pores The PGU model is modified from the porous-grain-stiff-sand （PGST） model by replacing the critical porosity with the more practical isolated porosity. In the implementation, the effective elastic constants of the porous grains are calculated by using the differential effective medium （DEM） model. Then, the elastic constants of connected porous grains in dry rocks are calculated by using the modified upper Hashin-Shtrikman bound. The application to the Tarim carbonates shows that relative to other conventional effective medium models the PGU model matches the well log data well.     

Response of fish communities in rivers subjected to a high sediment load

Erosion and sediment yield are a significant problem in the Guadalquivir River basin. Such phenomena are largely driven by a land use devoted to intensive cultivation of olive trees, with a large socioeconomic influence in Andalusia. This sediment overload in rivers causes serious impacts on all fluvial ecosystem components.In this study we assess the chronic effect of sediment yield on fish communities at 104 river sites located in two different sub-catchments – the Bembézar and Guadajoz rivers – both with different lithological composition and erosion rates. Sediment yield was estimated using a semi-quantitative Factorial Score Model (FSM), developed specifically for Spanish rivers. The fish populations of both basins were evaluated in composition and abundances by the study of Fernández-Delgado et al., 2014. The influence of sediment yield on the fish community was analyzed using General Additive Models.The sediment yield was higher in the Guadajoz basin (921 T/Km2 per year) than in Bembézar (701 T/Km2 per year). In the former, fish communities were poorer in both fish density and diversity, with Luciobarbus sclateri as the only substantially present species and a significant relationship between sediment yield and load, and fish density. In contrast, in the Bembézar basin, sediment yield was correlated with total fish density, including Luciobarbus sclateri, Pseudochondrostoma willkommii, Cobitis paludica, Iberochondrostoma lemmingii, Anaecypris hispanica, and Cyprinus carpio. Intermediate values of sediment yield led to maximum densities, while those higher decreased the density of these species.     

据地壳速度结构推测1668年山东郯城8?级大地震震中

The deep structure features around Tancheng M8 /2 earthquake occurred in 1668 have been analyzed. Based on the crustal velocity structure obtained from travel-time tomographic inversion, especially the low velocity zones in middle crust and Moho depths, the deep velocity structure distribution in the area of 34° ~ 36°N, 118° ~ 119°E is scanned along the latitude, longitude and oblique directions, and the corresponding crustal velocity profiles are obtained. By comparison, we take the area with velocity features coincident to the deep structure of the 1668 Tancheng M8/2 earthquake as the deduced epicenter, which is at 34. 8° ~35. 2°N, 118. 2° ~ 118. 7°E, and the reasonable location is 35. isN, 118. 6°E, and the focal depth is 20km.     

福建仙游地震序列的震源机制解

1,209 earthquakes occurred in Xianyou, Fujian from August 4, 2010 to October 4, 2013. The largest earthquake was ML5.0 on September 4, 2013. In order to study the Xianyou earthquake sequence and understand the causative structure and stress field of Xianyou, the focal mechanism solutions of six earthquakes （ ML 〉 3. 5 ） in the Xianyou earthquake sequence are calculated using the broadband digital data of the Fujian Seismic Network with the seismic moment tensor inverse method. The results show that the focal faults of the six earthquakes are similar, which are all strike-slip faults striking to the northwest with high dip angles. The direction of the principal compressive stress axes is near SN, which is different from the stress field of Fujian region. The Xianyou earthquake sequence may have been induced by the stress adjustment after the impoundment of Jinzhong reservoir.     

新疆全区和分区地壳速度模型的分析

In this paper, we firstly analyze the ＂3,400 travel time table＂ used for a long time in Xinjiang Seismological Network to obtain the velocity structure models in accord with the table by fitting. Then we fit the velocity of all seismic phases recorded in Xinjiang region in January 2009 ~ December 2013. Simulation analysis is done on the reliability and stability of the velocities, and a concept is proposed for building subarea crustal velocity models according to partitioning of seismic cluster regions. The crustal velocity model suitable for the Yutian area is fitted with the data of all phases of seismic events within a radius of 1 ° around the 2014 Yutian Ms7. 3 earthquake since January 2009, and the model is applied to the relocation of the Yutian Ms7. 3 earthquake and determination of focal depths of the earthquake sequence.     

云南洱海桃溪河口净化工程的设计思路及初步净化效果

以太湖上游西苕溪流域为研究对象,通过分布式水文模型HEC-HMS模拟次降雨洪水过程:采用可视化数据存储系统HEC-DSS建立水文气象数据库,利用Geodatabase地理数据库技术集成流域自然属性数据库,通过距离平方倒数法对雨量数据进行空间插值,SCS曲线数法计算水文损失,运动波法计算直接径流与河道洪水演进,选用基流指数退水法模拟流域基流,并对模型中水库模拟部分进行适当修正.经模型校验,模拟结果表明,计算流量与观测流量拟合较好,效率系数大于0.8,洪峰流量误差低于4%,峰现时间误差低于2 h,该模型在土地利用变化对洪水水文要素的影响研究方面有较好的应用前景.     

Effects of landuse change on surface runoff and sediment yield at different watershed scales on the Loess Plateau

Erosion and sediment yield from large and small watersheds exhibit different laws. Variations in surface runoff and sediment yield because of landuse change in four watersheds of different scales from 1 km2 to 73 km2 were analyzed. Due to reforestation and farmland terracing, surface runoff and sediment yield reduced by 20-100% and 10-100% respectively. Reductions in surface runoff were differed significantly under different precipitation regimes. For the large watershed (73 km2) landuse change had similar effects on surface runoff regardless of changing of precipitation. For the small watershed (1 km2) landuse change had fewer effects on surface runoff under high precipitation. The relative changes of sediment yield in the four watersheds under reforestation and farmland terracing decreased as precipitation increased from 350 mm to 650 mm, then increased as precipitation increased from 650 mm to 870 mm. Where initial forest coverage rate was below 45%, sediment yield decreased dramatically as forest coverage rate increased. Watershed management with aiming at reducing both surface runoff and sediment yield should be conducted both on sloping surfaces and in channels in large watersheds.     

Earthquake magnitude estimation using the τc and Pd method for earthquake early warning systems

Earthquake early warning （EEW） systems are one of the most effective ways to reduce earthquake disaster. Earthquake magnitude estimation is one of the most important and also the most difficult parts of the entire EEW system. In this paper, based on 142 earthquake events and 253 seismic records that were recorded by the KiK-net in Japan, and aftershocks of the large Wenchuan earthquake in Sichuan, we obtained earthquake magnitude estimation relationships using the τe and Pa methods. The standard variances of magnitude calculation of these two formulas are ±0.65 and ±0.56, respectively. The Pd value can also be used to estimate the peak ground motion of velocity, then warning information can be released to the public rapidly, according to the estimation results. In order to insure the stability and reliability of magnitude estimation results, we propose a compatibility test according to the natures of these two parameters. The reliability of the early warning information is significantly improved though this test.     

The effect of soil type,meteorological forcing and slope gradient on the simulation of internal erosion processes at the local scale

Numerical simulation experiments of water erosion at the local scale (20 × 5 m) using a process‐based model [Plot Soil Erosion Model_2D (PSEM_2D)] were carried out to test the effects of various environmental factors (soil type, meteorological forcing and slope gradient) on the runoff and erosion response and to determine the dominant processes that control the sediment yield at various slope lengths. The selected environmental factors corresponded to conditions for which the model had been fully tested beforehand. The use of a Green and Ampt model for infiltration explained the dominant role played by rainfall intensity in the runoff response. Sediment yield at the outlet of the simulated area was correlated positively with rainfall intensity and slope gradient, but was less sensitive to soil type. The relationship between sediment yield (soil loss per unit area) and slope length was greatly influenced by all environmental factors, but there was a general tendency towards higher sediment yield when the slope was longer. Contribution of rainfall erosion to gross erosion was dominant for all surfaces with slope lengths ranging from 4 to 20 m. The highest sediment yields corresponded to cases where flow erosion was activated. An increase in slope gradient resulted in flow detachment starting upstream. Sediment exported at the outlet of the simulated area came predominantly from the zone located near the outlet. The microrelief helped in the development of a rill network that controlled both the ratio between rainfall and flow erosion and the relationship between sediment yield and slope length. Copyright © 2010 John Wiley & Sons, Ltd.     

Sediment yield from glacio-lacustrine calcareous deposits during the postglacial period in the Combe d’Ain (Jura,France)

The middle valley of the river Ain (Jura) cuts through glacio-lacustrine deposits laid down in an ice-dammed lake during the most recent glacial advance. The total volume eroded is about 6·21 × 10⁸ m³for a surface area of 3·7 × 10⁷ m². Erosion occurred between 18 ka BP and 6 ka BP , i.e. over a duration of some 12 ka. Sediment yield from the area was of the order of 2500 t km⁻² a⁻¹, which is comparable with modern-day sediment yield from NW African badlands. These high values are ascribed to the amenability of glacio-lacustrine deposits to mechanical weathering and to the rapid geomorphological changes that affected glacial and paraglacial sedimentary cover after the retreat of the ice. The valley slopes were destabilized by mass wasting (earthflow and mudflow), which was the predominant erosional process. The slopes are currently stabilized or very exceptionally active. © 1998 John Wiley & Sons, Ltd.     

Comparative assessment of two distributed watershed models with application to a small watershed

Distributed watershed models are beneficial tools for the assessment of management practices on runoff and water‐induced erosion. This paper evaluates, by application to an experimental watershed, two promising distributed watershed‐scale sediment models in detail: the Kinematic Runoff and Erosion (KINEROS‐2) model and the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model. The physics behind each model are to some extent similar, though they have different watershed conceptualizations. KINEROS‐2 was calibrated using three rainfall events and validated over four separate rainfall events. Parameters estimated by this calibration process were adapted to GSSHA. With these parameters, GSSHA generated larger and retarded flow hydrographs. A 30% reduction in both plane and channel roughness in GSSHA along with the assumption of Green‐Ampt conductivity K_G‐A = K_s, where K_s is the saturated conductivity, resulted in almost identical hydrographs. Sediment parameters not common in both models were calibrated independently of KINEROS‐2. A comparative discussion of simulation results is presented. Even though GSSHA's flow component slightly overperformed KINEROS‐2, the latter outperformed GSSHA in simulations for sediment transport. In spite of the fact that KINEROS‐2 is not geared toward continuous‐time simulations, simulations performed with both models over a 1 month period generated comparable results. Copyright © 2006 John Wiley & Sons, Ltd.     

An un-mixing model to study watershed erosion processes

An un-mixing model is formulated within a Bayesian Markov Chain Monte Carlo framework for use within land-use fingerprinting to study watershed erosion processes. The model has two new components: (1) An equation and erosion process parameter are used to weight tracer signatures from each erosion process within a land-use. (2) An extra tracer distribution and episodic erosion parameter are used to represent soil eroded throughout the sampling duration and thus include the episodic nature of erosion. To test specification of these new parameters, the un-mixing model is applied in the 15 km² Jerome Creek Watershed in the Palouse Region of Northwestern Idaho. Erosion processes include surface erosion upon mountain slopes due to logging in the forest land-use and rill/interrill erosion on cultivated slopes and headcut erosion in riparian floodplains of the agricultural land-use (winter wheat/peas rotation and hay pasture). Episodic erosion occurs for the event where the model is applied. A sensitivity analysis shows that the smallest Bayesian credible set results when the new parameters are specified using hydrologic data and process-based models. The un-mixing model predicts that 90% of the eroded-soil originated from the agricultural land-use and 10% originated from the forest land-use. A comparative study is performed that estimates 90.5% and 9.5% of eroded-soil originated from the agricultural and forest land-uses. Successful performance of the un-mixing model highlights future application as a standalone probabilistic tool to monitor watershed erosion processes that exhibit non-equilibrium conditions and provide calibration data for process-based watershed models.     

Hydrologic modeling,parameter estimation,and watershed characteristics

A general watershed model represents the runoff phase of the hydrologic cycle by a series of moisture accounting equations. The Stanford Watershed Model uses fixed equations containing variable parameters which are calibrated for a watershed by trial-and-error matching of simulated to recorded flows. Opset was developed to estimate these parameters through a computerized least squares matching. The procedure reduces estimating scatter and provides parameter estimates which were correlated with physical characteristics of the watershed and with watershed changes with urbanization.     

Processes of accelerated pluvial erosion on desert hillslopes modified by vehicular traffic

Accelerated pluvial erosion on hillslopes modified by off-road vehicles (ORVs) is analysed using results from 50 rainfall simulation experiments conducted in the Mojave Desert, California. Sediment yield from 1 m² hillslope plots subjected to intense, 20-minute rainfalls is typically increased 10 to 20-fold following ORV use. Salient effects of vehicle traffic, which reduce infiltration, increase runoff sediment transport efficiency, and enhance gully formation, are further studied by combining simple theoretical relations with experimental data. This analysis helps identify factors controlling erosion on natural desert hillslopes, as well as those used by ORVs. Erosion of natural or vehicle-used desert surfaces is heavily influenced by runoff hydraulics. Calculated Darcy-Weisbach friction factors decrease by an average of 13-fold following vehicular slope modification, whereas runoff Reynolds numbers increase by an average of 5 1/2-fold. The capacity of overland flow to transport sediment is related to runoff power and its degree of localization, which usually increase considerably following ORV activity; however, the ability of overland flow to move large grains (competency) is related to a combination of factors not always systematically influenced by ORV use. Kinematic runoff routing, which is used to extrapolate experimental results to longer slope lengths, leads to the suggestion that the hydraulic roughness of desert hillslopes strongly influences their erosional behaviour.     

THEME 1A DERIVATION OF EROSION AND SEDIMENT YIELD PARAMETERS IN AREAS WITH DEFICIENT DATA-RECONNAISSANCE MEASUREMENTS

Abstract

After defining the several terms that have come to be used to describe basins of various types this paper deals with some of the problems of basin studies. The relative sizes of different basins is one such problem, overland flow and interflow are others. Simulation of basins is considered, particularly the use of the Stanford Watershed Model and how this model can be applied to investigate changes due to urbanization and deforestation. The future role of representative and experimental basins is discussed.     

半湿润流域水文模型比较与集合预报

选择7种水文模型分别在中国北部3个半湿润流域做模拟对比,分析不同水文模型在各流域的适用性,并使用贝叶斯模型平均法对不同模型集合,比较各种集合方法的优势,研究贝叶斯模型平均法的应用效果.研究结果表明,以蓄满产流模式为主的模型在半湿润流域应用效果较好,针对不同流域特点对传统模型进行改进可以提高模拟精度.贝叶斯模型平均法能提供较好的确定性预报结果和概率预报结果,仅对少数模拟效果好的模型进行集合,并不能有效提高预报精度,适当增加参与集合的模型数量能使贝叶斯模型平均法更好地综合各模型优势,提高预报结果的精度.