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MACROPORE FLOW AND MASS WASTING OF GULLIES IN THE LOESS PLATEAU, CHINA

International Journal of Sediment Research 2005年第3期20卷 95-104页

作者： G. V. WILSON,M. J. M. RMKENS USDA-ARS National Sedimentation Laboratory 598 McElroy dr. Oxford ms 38655 dr. USDA-ARS National Sedimentation Laboratory 598 McElroy dr. Oxford ms 38655 prof. dr.

Due to the extensive gullying from historically excessive erosion in the loess plateau of China, much of this region is being converted to native grass and shrub vegetation. Tunnel scour and mass wasting are important gully erosion processes resulting from preferential flow through macropores ( pores > 1 mm diameter). The objective of this study is to assess the changes with time in macropore flow characteristics of soils on the Loess Plateau following conversion to grass vegetation and the associated degree of mass wasting of gully faces. Ridge areas that had been revegetated for 1 year, 6 years, and > 15 years following tilling, and for 6 years following contour-ditching and the adjacent gully faces were characterized for their macropore and soil matrix properties on a 50 cm by 50 cm area. The total number of macropores increased from 11.6/m2 to 39.6/m2 from 1 to 6 years and to 51.6/m2 after 15 years of revegetation following tillage. The macroporosity increased from 0.0008 m3/m3 to 0.0018 m3/m3 from 1 to 6 years of revegetation following tillage but the lowest macroporosity (0.0005 m3/m3) was 6 years of revegetation following contour-ditching. The contour-ditched area had the lowest infiltration rate (95 m/d) through the soil matrix (areas without macropores) with the tilled areas having similar infiltration rates regardless of the number of years of revegetation (averaged 146 m/d). Due to tunnel scour erosion of macropores during infiltration into the area revegetated for 1 year, pore diameters enlarged by more than 200% resulting in this condition having the highest individual macropore infiltration rates (7967 m/d). Macropores in all other areas were stable with no tunnel scour erosion of macropores. The total capacity for infiltration through macropores increased significantly with time following revegetation. The number of macropores on the gully faces was triple (92.8/m2) and the macroporosity quadr.ple (0.004 m3/m3) that of the ridge surfaces. The upper gu

关键词： Pipe flow Macropores Infiltration Mass wasting Gully erosion

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Mitigation of atrazine,S-metolachlor,and diazinon using common emergent aquatic vegetation

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Journal of Environmental Sciences 2017年第6期29卷 114-121页

作者： Matthew T.Moore Martin A.Locke Robert Krǒger Water Quality and Ecology Research Unit USDA Agricultural Research ServiceNational Sedimentation LaboratoryOxfordMS 38655USA

By the year 2050, the population of the United States is expected to reach over 418 million, while the global population will reach 9.6 billion. To provide safe food and fiber, agriculture must balance pesticide usage against impacts on natural resources. Challenges arise when storms cause runoff to be transported to aquatic receiving systems. Vegetated systems such as dr.inage ditches and constructed wetlands have been proposed as management practices to alleviate pesticide runoff. Twelve experimental mesocosms （1.3 ±0.71 ± 0.61 m） were filled with sediment and planted with a monoculture of one of three wetland plant species （Typha latifolia, Leersia oryzoides, and Sparganium arnericanurn）. Three mesocosms remained unvegetated to serve as controls. All mesocosms were amended with 9.2 ± 0.8 μg/L, 12 ± 0.4 μg/L, and 3.1 ± 0.2 μg/L of atrazine, metolachlor, and diazinon, respectively, over a 4 hr hydr.ulic retention time to simulate storm runoff. Following the 4 hr amendment, non-amended water was flushed through mesocosms for an additional 4 hr. Outflow water samples were taken hourly from pre-amendment through 8 hr, and again at 12, 24, 48, 72, and 168 hr post-amendment. L. oryzoides and T. latifolia had mean atrazine, metolachlor, and diazinon retentions from B1%-55% for the first 4 hr of the experiment. Aside from S. arnericanum and atrazine （25% retention）, unvegetated controls had the lowest pesticide retention （17%-28%） of all compared mesocosms. While native aquatic vegetation shows promise for mitigation of pesticide runoff, further studies increasing the hydr.ulic retention time for improved efficiency should be examined.

关键词： Phytoremediation Pesticide Mesocosm Wetland

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dr.dging effects on selected nutrient concentrations and ecoenzymatic activity in two dr.inage ditch sediments in the lower Mississippi River Valley

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International Soil and Water Conservation Research 2017年第3期5卷 190-195页

作者： Matt Moore Martin A.Locke Michael Jenkins Robert W.Steinriede Daniel S.McChesney USDA-Agricultural Research Service National Sedimentation Laboratory598 McElroy DriveOxfordMS 38655USA

Agricultural dr.inage ditches are conduits between production acreage and receiving aquatic *** overlooked for their mitigation capabilities,agricultural dr.inage ditches provide an important role for nutrient transformation via microbial *** in ecoenzyme activities have been used to elucidate microbial metabolism and resource demand of microbial communities to better understand the relationship between altered nutrient ratios and microbial activity in aquatic *** agricultural dr.inage ditches,one in the northeast portion of the Arkansas Delta and the other in the lower Mississippi Delta,were monitored for a *** samples were collected prior to each ditch being dr.dged(cleaned),and subsequent post-dr.dging samples occurred as soon as access was *** samples were then collected throughout a year to examine effects of dr.dging on selected nutrient concentrations and ecoenzymatic activity recovery in dr.inage ditch *** concentrations in sediments after dr.dging decreased 33–66%,depending on ditch and phosphorus extraction ***,ecoenzymatic activity was significantly decreased in most sediment samples after *** diacetate hydr.lysis activity,an estimate of total microbial activity,decreased 56–67%after dr.dging in one of the two *** sample sites also had significant phosphorus and ecoenzymatic activity differences between the post-dr.dge samples and the year-long follow-up *** indicate microbial metabolism in dr.dged dr.inage ditches may take up to a year or more to recover to pre-dr.dged ***,while sediment nutrient concentrations may be decreased through dr.dging and removal,runoff and erosion events over time tend to quickly replenish nutrient concentrations in replaced *** nutrient dynamics and microbial metabolism within agricultural dr.inage ditches is a crucial step toward addr.ssing issues of nutri

关键词： Phosphorus FDA Denitrification Mehlich III Microbial Metabolism

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MODELING HEADCUT DEVELOPMENT AND MIGRATION IN UPLAND CONCENTRATED FLOWS

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International Journal of Sediment Research 2005年第4期20卷 281-294页

作者： Sean J. BENNETT Carlos V. ALONSO Department of Geography University at Buffalo Buffalo NY 14261-0055 USA USDA-ARS National Sedimentation Laboratory P.O. Box 1157 Oxford MS 38655

On hillslopes and agricultural fields, discrete areas of intense, localized soil erosion commonly take place in the form of migrating headcuts. These erosional features significantly increase soil loss and landscape degradation, yet the unsteady, transient, and migratory habits of headcuts complicate their phenomenological and erosional characterization. Here a unique experimental facility was constructed to examine actively migrating headcuts typical of upland concentrated flows. Essential components of the facility include a deep soil cavity with external dr.inage, rainfall simulator, capacity for overland flow, and a video recording technique for data collection. Results from these experiments show that: (1) after a short period of adjustment, headcut migration attained a steady-state condition, where the rate of migration, scour hole geometry, and sediment discharge remain constant with time; (2) boundary conditions of higher rates of overland flow, steeper bed slopes, and larger initial headcut heights produced systematically larger scour holes with higher rates of soil erosion; and (3) during migration, the turbulent flow structure within the scour hole remained unchanged, consisting of an overfall nappe at the brink transitioning into a reattached wall jet with two recirculation eddies within the plunge pool. The systematic behavior of headcut development and migration enabled the application of modified jet impingement theory to predict with good success the characteristics of the impinging jet, the depth of maximum scour, the rate of headcut migration, and the rate of sediment erosion. These laboratory data and the analytical formulation can be used in conjunction with soil erosion prediction technology to improve the management of agricultural areas impacted by headcut development and ephemeral gully erosion.

关键词： Soil erosion Headcuts Rills Gullies Jet impingement

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Influence of Geomorphology on Fish Fauna of a Small Mississippi Bluffline Stream

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Journal of Environmental Science and Engineering(B) 2015年第4期4卷 169-176页

作者： Scott Stephen Knight Terry Douglas Welch United States Department of Agriculture Agricultural Research Service National Sedimentation Laboratory Oxford MS 38655 USA

Fish were collected from 39 sites on the main channel and major tributaries of a highly erosive stream, Hotophia Creek. A total of 2,642 specimens representing 38 species were collected between 1986 through 2003. The bluntface shiner Cyprinella camura was the dominant species of fish and when grouped with other cyprinids accounted for 38.0% of the total numbers collected. By weight, Lepisosteusoculatus, Lepomismegalotis, lctiobusbubalus, and Lepomismacrochirus were the dominant species; accounting for 49.9% of the total catch. While more diminutive species such as cyprinids that might be subject to predation by large fish more frequently were found in shallow channels. Fishes with specific habitat requirement such as the pirate perch were found in the middle group of sites, that were disturbed by erosion process but that featured the necessary habitat requirements. Sensitive or intolerant species like the Yazoo darter, creek chubsucker and cyprinids in general were more frequently found in the undisturbed and habitat complex channels. This study supports the hypothesis that geomorphological stream stages are associated with specific communities of fishes.

关键词： Stream classification geomorphology index of biotic integrity ecology.

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HYdr.LOGICALLY dr.VEN MECHANISms OF HEADCUT DEVELOPMENT

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International Journal of Sediment Research 2005年第3期20卷 22-30页

作者： M. J. M. RMKENS,S. N. PRASAD USDA-ARS National Sedimentation Laboratory Oxford ms 38655 USA Department of Civil Engineering University of Mississippi University ms 38677 USA

An analytic investigation of the effect of surface seal mechanical properties, overland flow, and subsurface hydr.logy was performed on headcut development. Headcut growth rates on upland areas have been observed to be quite small (less than 0.00015 meter per second) and that they occur in increments in which chips break off at points where cracks have developed in surface seals. The substrate soil under the seal collapses and is removed by the flow. This mode of headcut development is the result of a strong interaction between the surface and the subsurface processes. The surface process is energetically controlled by the mechanical features of the seal whereas the subsurface process is hydr.logically controlled. The analysis yields estimates of the temporal scale of headcut velocities. In cases of infiltration from the vertical gully wall into the substrate, the flexural wave velocity (seismic sound velocity) was found to inversely affect headcut velocity.

关键词： Surface seal Subsurface Headcut Soil erosion Overland flow

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Control of Agricultural Nonpoint Source Pollution by Natural Wetland Management

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Journal of Environmental Science and Engineering 2010年第4期4卷 62-70页

作者： F.D. Shields Jr C.W. Pearce Water Quality and Ecology Research Unit USDA-ARS National Sedimentation Laboratory Oxford MS 38655-1157 USA

Reduction ofnonpoint source pollutants, principally sediment and nutrients moving from cultivated fields to surface waters, is a major challenge. Remnants of once-extensive natural wetlands occur across the agricultural landscape, and it has been suggested that these areas might be managed to yield improved wetland function in terms of trapping and retention of nonpoint source pollutants. An existing wetland in a severed meander bend cut off in the 1940s from the Coldwater River in Tunica County, ms, USA was modified by the construction of weirs equipped with water control structures. The wetland was a segment o fold river channel about 500 m long and 20 m wide. Inputs to the wetland cell included sporadic flows due to runoff events from about 350 ha of cultivated fields and less frequent but larger flood events from the river. This type of flood event occurred only once during the study. Concentrations of sediment and nutrients in water were generally lower at the downstream end of the wetland cell than in the major inflow, an ephemeral slough. Mean values of turbidity, suspended sediment concentration, and concentrations of filterable and total phosphorus were 25% to 40% lower at the wetland cell discharge weir than in the slough. Mean concentrations of ammonia were 38% lower, but mean nitrate and nitrite concentrations were essentially unchanged by the wetland cell. Comparison of estimated input and output loads during periods when the wetland cell was not flooded by the river indicated that the wetland cell retained about 18% of input suspended sediment, 24% of phosphorus, and 29% of nitrogen input from cultivated fields. Wetland cell sediment and nutrient retention efficiency was treater for dr.er months, and declined durin~ wetter periods with frequent runoff events.

关键词： Agriculture nutrients sediments wetlands ecological engineering.

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河岸带潜流层动态过程与生态修复

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水科学进展 2013年第4期24卷 589-597页

作者：夏继红陈永明王为木韩玉玲刘海洋胡玲河海大学水利水电学院 National Center for Computational Hydr.science and Engineering the University of MississippiMS Oxford 38655 USA 浙江省河道管理总站

河岸带潜流层是河岸带内地表水与地下水相互作用的生态交错带,在水文地理学、生态学、环境学上含义不尽相同。河岸带潜流层具有复杂的垂向、横向、纵向结构特征,其边缘效应显著,表现为泥沙、水流、生物、环境化学因子之间的复杂动态过程... 详细信息

河岸带潜流层是河岸带内地表水与地下水相互作用的生态交错带,在水文地理学、生态学、环境学上含义不尽相同。河岸带潜流层具有复杂的垂向、横向、纵向结构特征,其边缘效应显著,表现为泥沙、水流、生物、环境化学因子之间的复杂动态过程,主要包括水动力动态过程、生态学过程、溶质循环与化学过程等。水动力动态过程是驱动条件,氧气浓度是生态过程、溶质循环和化学过程的决定性因素。在各动态过程的驱动下,河岸带潜流层具有调蓄洪水、削减污染、净化缓冲环境和提供适宜栖息地等功能。针对河岸带潜流层功能退化的问题,需开展健康诊断,明确致病机理,实施适宜的生态修复。未来中国在开展河岸带潜流层研究时,应根据中国河岸带特点,采用示踪试验、数值模拟等方法,集成GIS等现代技术手段,研究多尺度下,水文条件、地形变化、土壤渗透系数、河岸带建设方式、植被分布等对河岸带潜流层水文、热传导、生化、生态等的影响机制,准确界定河岸带潜流层区域范围,制定适宜的生态修复策略。

关键词：河岸带潜流潜流生物边缘效应生态修复

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Spatial-temporal Pattern and Population dr.ving Force of Land Use Change in Liupan Mountains Region, Southern Ningxia, China

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Chinese Geographical Science 2008年第4期18卷 323-330页

作者： QUAN Bin M J M ROMKENS TAO Jianjun LI Bicheng LI Chaokui YU Guanghui CHEN Qichun Institute of Geospatial Information Science Hunan University of Science and Technology Xiangtan 411201 China USDA/ARS National Sedimentation Laboratory P O. Box 1157 Oxford MS 38655 USA Researeh Center of Soil and Water Conservation and Ecological Environment Chinese Academy of Sciences and Ministry of Education Northwest Sci-tech University of Agriculture and Forestry Yangling 712100 China

The Liupan Mountains is located in the southern Ningxia Hui Autonomous Region of China, which forms an important dividing line between landforms and bio-geographic regions. The populated part of the Liupan Mountains region has suffered tremendous ecological damages over time due to population pressure, excessive demand and inappropriate use of agricultural land resources. In this paper, datasets of land use between 1990 and 2000 were obtained from Landsat TM imagery, and then spatial models were used to characterize landscape conditions. Also, the relationship between the population density and land use/cover change (LUCC) was analyzed. Results indicate that cropland, forestland, and urban areas have increased by 44,186ha, 9001ha and 1550ha, respectively while the grassland area has appreciably decreased by 54,025ha in the study period. The decrease in grassland was most notable. Of the grassland lost, 49.4% was converted into cropland. The largest annual land conversion rate in the study area was less than 2%. These changes are attributed to industrial and agricultural development and population growth. To improve the eco-economic conditions in the study region, population control, urbanization and development of an ecological friendly agriculture were suggested.

关键词： land use/cover change (LUCC) GIS remote sensing Liupan Mountains region Loess Plateau

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Effects of Channelization on Fish Biomass in River Ecosystems

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Journal of Environmental Science and Engineering(A) 2012年第8期1卷 980-985页

作者： Scott S. Knight R.F. Cullum F.D. Shields Jr. P.C. Smiley USDA-ARS National Sedimentation Laboratory Oxford 38655 MS USA USDA-ARS-Soil dr.inage Research Unit Columbus 43210 OH USA

Channel straightening in a naturally meandering river is a common historical trigger of channel incision which typically results in stream bank destabilization. Several of the larger river systems in the upland portion of the Yazoo River Basin have subjected channelization resulting in prof.und changes in the physical and geomorphological characteristics of these systems. Fish were sampled using electroshocking gear and hoop nets to evaluate the impact of stream bank destabilization and loss of habitat heterogeneity resulting from channelization on fish communities. While distinct differences in the fish communities were evident, only the Skuna appeared to have characteristics of a damaged system. More than 95% of the biomass was comprised of species reaching an adult length of less than 300 mm. The lotic omnivorous fishes that dominated the biomass from Skuna are often associated with smaller streams rather than rivers. Furthermore, 72% of the catch consisted of fish preferring littoral zone habitats. The shallow depth and lack of woody debris in Skuna provided a selective advantage for smaller species of fish that could use shoreline habitats as protection from the current. Based on results from the Skuna River, channel straightening that leads to channel incision, bank failure and over widening provide habitats too shallow to support a community of fishes typical of northern Mississippi riverine system. This information may be useful in making comparison of damaged riverine ecosystems and assist managers in determining impairment and success in the TMDL （Total Maximum Daily Load） process.

关键词： Channel incision channel straightening fish biomass.

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