辽宁西部沿海地区无观测流域水文相似性分析

基于辽宁西部海岸带小流域的气象、地形地貌、土地利用、土壤分布等要素,构建了流域间水文相似指标体系。利用层次分析法依据水文相似性度原理判别流域间水文的相似性,为解决在不同流域间实现水文参数移植提供依据。     

基于主成分分析法的嵌套流域水文相似性研究

以全国不同地区的4个典型嵌套流域为研究对象,利用主成分分析法将流域地形地貌、土壤植被等32个特征指标降维后进行水文相似性分析,发现下会流域子流域的水文特征基本相似,其他3个流域相似度都较低。为验证基于主成分的水文相似性分析结果,建立各子流域的降雨径流相关图,并分别将每个嵌套流域下子流域的相关图综合到一张图上,计算综合前后径流深合格率,仅有下会流域的合格率变幅在可接受范围内。结果表明,基于主成分分析嵌套流域的水文相似性是合理的,嵌套流域内水文相似度较高的子流域可用同一条降雨径流关系线来表示。     

长江上游流域暴雨洪水相似性判别指标研究

暴雨洪水发生演化的各个阶段之间存在一定的关联性和规律性。以长江上游流域为研究对象,将暴雨洪水指标分为降雨、洪水、时间、雨洪关系、水库、形状和初始指标7大类,共67个指标。通过整理暴雨历史洪水资料,摘录暴雨洪水过程和计算暴雨洪水特征值,结合洪量相似度、洪峰相似度、形状相似度和灰色关联度4种相似性评价方法,优选出降水量、降水历时、起涨流量和洪水涨率4个指标作为相似洪水判别指标。以113场三峡入库洪水为样本进行相似性检验,基于几场典型洪水特征值寻找的历史相似洪水之间的相似度较高,确定性系数都达到了0.9以上。结果表明,降水量、降水历时、起涨流量和洪水涨率4个指标作为相似洪水判别指标,对指导实时洪水预报具有较高的参考价值。研究成果在三峡水库以上长江上游流域进行了试验应用,在寻找历史相似洪水方面具有较好的效果。     

无资料地区洪水预报参数估计

以广州市流溪河流域内流溪河水库、黄龙带水库、和龙水库等9个水库子流域为研究对象,根据已知出库流量及库容曲线反推入库流量,基于三水源新安江模型进行洪水预报。假定芙蓉嶂水库为无资料地区,根据气象预报及其余8个子流域的流域特征值进行参数移植,建立流域特征值和敏感性参数的多元回归方程,对比分析距离相近法、面积相似法、参数平均法与多元回归法的参数移植结果,发现多元回归法移植效果较好,预报结果达到乙级精度。     

基于WRF模式的大渡河流域径流预报模型

针对大渡河流域地形复杂,高差悬殊,气候垂直差异大等特点,构建基于四层嵌套网格的大渡河流域WRF模型:采用四维变分(4DVar)和集合卡曼滤波(EnKF)混合同化技术降低初始场误差,根据统计最优组合方法确定年内不同时期WRF模式参数方案集.将WRF输出作为预见期内新安江模型的输入,构建大渡河流域WRF-新安江来水预报模型...     

官厅密云流域土地利用/覆盖与景观格局分析

通过对1980年、2000年和2008年3期遥感影像数据进行解译,结合土地利用/覆盖和景观生态学中的研究方法,利用ArcGIS等软件分析了官厅密云流域1980—2008年的土地利用/覆盖和景观格局指数变化。结果表明:1980—2008年,流域土地利用/覆盖类型以旱地、林地和草地为主的格局并没有随时间的改变而改变,三者面积之和约占流域总面积的93%左右。林地和草地的面积总和略有下降,流域植被覆盖处于退化的趋势;建设用地面积不断增加。28 a来,流域内建设用地、水田和水域的动态度一直较大,变化较为明显;土地利用程度综合指数一直增加,说明官厅密云流域土地利用/覆盖一直处于调整发展时期。水域的分维数最大,建设用地的分维数一直在增加;建设用地、未利用土地和水域的破碎度较大;香农多样性指数和香农均匀度指数略有下降,说明流域内景观类型多样性降低、分布出现不均衡化特征。     

基于子流域的TOPMODEL模拟研究

 TOPMODEL是根据水文相似性——地形指数相同的栅格划分为同一产流单元进行产流计算,但是其不能考虑降雨和地形指数统计分布曲线等流域地形地貌信息的空间不均匀性。通过对流域DEM处理,建立了基于水系子流域的TOPMODEL。该模型考虑了降雨、地形指数分布曲线等空间不均匀性。将基于子流域的TOPMODEL和TOPMODEL应用在九州流域,并进行模拟比较,发现基于子流域的TOPMODEL更能反映流域的实际情况,模拟的结果更加合理。可以预测不同子流域降雨组合下的流域出口的流量过程。     

分布式水文模型在嵌套流域的应用与研究

基于物理基础的分布式水文模型通常用于详细描述小尺度流域的水文过程,在大尺度中应用时存在参数模拟问题。为了研究具有物理意义的模型参数随尺度变化的规律,将CASC2D模型应用于月潭、呈村组成的嵌套流域,对比分析了嵌套流域和流域内部网格模拟值的精度。结果表明:1嵌套流域内产流参数变化较小,汇流参数与流域尺度有一定的关系,随着流域面积的增大,坡面汇流糙率和河道汇流糙率均增大;2呈村流域模拟精度较高,降雨数据及其时空分布会对模拟精度产生重要影响;3模型对流域内部点的计算结果存在误差且异参同效的现象普遍存在。     

基于GIS的南渡江流域生态敏感性评价

为了解南渡江流域生态环境遭到破坏的程度,基于GIS技术,根据南渡江流域的主要生态问题,选取高程、坡度、地形起伏度、土壤侵蚀、土地覆盖、水体缓冲、降雨侵蚀力和植被覆盖度8个生态敏感性评价指标,采用层次分析法(AHP)、多因子加权求和模型以及自然断点法,将流域划分为5个生态敏感等级。结果表明南渡江流域整体生态敏感性适中,其评价结果可为政府相关部门在南渡江流域的生态保护和资源开发中提供依据和参考。     

土地利用变化下的水文响应及其可检测性分析

以涪江桥流域为研究区域,采用SWAT模型模拟流域水文过程,将相同水文气象条件下1985和1995年2个时期土地利用情景的SWAT模型模拟结果与土地利用空间转化图相结合,分析土地利用变化引起的水文要素变化及其可检测性问题。结果表明:1985—1995年间涪江桥流域发生较为剧烈的土地利用变化,但并未检测到足够显著的水文要素变化;不同土地利用类型水文效应的相似性、不同土地利用类型水文效应差异性以及统计中和效应和统计均化效应是导致土地利用变化引起的水文要素变化难以检测的主要原因。在此基础上,提出了水文动态响应度指标,来消除统计中和效应。该指标可以在一定程度上帮助研究者了解研究区特定水文要素变化的相对剧烈程度。研究结果可为土地利用总体规划和流域水资源保护与合理配置提供参考。     

喀斯特峰丛-洼地小流域洪水滞时及相似性分析

以两个邻近的典型喀斯特峰丛-洼地小流域(陈旗和长冲)为研究对象,选取26场不同量级流量的洪水过程,对比分析陈旗流域地表、地下两套水系及其与长冲流域洪水的滞时和相似性特征。结果表明:陈旗流域受洼地不透水/弱透水跃迁部位的"门槛效应"影响,地表河与地下河的洪水滞时和形态特征差异明显,地表河洪水涨落迅速,但峰现时间滞后于地下河;流域暴雨洪水涨落形态受地表河控制,与地表河洪水形态相似度高。长冲流域暴雨洪水过程与地表洪水过程相似,随着降雨量的减小,其洪水形态趋向于地下河径流变化特征;流域不透水岩石分布减小了含水层调蓄能力,流域洪水滞留时间短、暴雨洪水响应迅速。     

Watersheds and stream networks viewed longitudinally: Example insights from novel spatial portrayals of watershed characteristics

Longitudinal depictions of watershed structure and characteristics, including topography, stream networks, wetlands, ground water levels, and land use, can provide watershed knowledge and understanding unavailable from standard plan view maps. Three case studies provide examples of knowledge gained by applying longitudinal views of stream networks, watershed hydrologic behavior, and land use distributions. Longitudinal views of mountain stream networks show extreme variability in the slope-area relationships of low Strahler order streams, large discontinuities in drainage area (large parts of drainage area space are absent in networks), and large variations in network curvature. Longitudinal views of a groundwater-dominated headwater watershed increase the inference available from limited groundwater observations and clearly reveal how groundwater connections affect the permanence of surface water features and the distribution of vadose zone storage in the landscape. Plotting land uses longitudinally illuminates and allows a quantitative analysis of how land uses are distributed relative to topographic position. Viewing watersheds and stream networks longitudinally can provide new insights into watershed forms and processes and motivate new questions and research.     

Elevated Nutrient Levels from Agriculturally Dominated Watersheds Stimulate Metaphyton Growth

The linkage between land use in a catchment basin and downstream aquatic ecosystems, especially effects on algae attached to substrata or loosely aggregated in the littoral zone, represents a void in our understanding of lake systems. The occurrence of beds of metaphyton at some stream mouths and not others in Conesus Lake, NY (USA) provided an opportunity to consider the relationship between land use and phosphorus and nitrogen losses on the development of shoreline metaphyton blooms. Experiments were performed in the littoral zone of a large temperate lake to test the hypothesis that effluent high in phosphorus and nitrate from tributaries draining agricultural watersheds had a stimulatory effect on the growth of littoral metaphyton, while effluent from a forested watershed did not. The study encompassed six watersheds of varying agricultural use (60–80%) and a forested watershed (12% agriculture). For each experiment, two quadruplicate sets of plexiglass incubation chambers (height = 50 cm, interior diameter = 9.5 cm) containing native assemblages of metaphyton received lake or tributary water continuously over a 3-day lake incubation period. Growth of metaphyton incubated in lake water and in tributary water was compared and differences appeared to be related to nutrient concentrations. A statistically significant stimulatory effect was measured for the six tributaries draining agricultural watersheds but not for the forested watershed. Tributary loadings appear to stimulate metaphyton at sites where the hydrology and hydrodynamincs are suitable. A significant positive linear relationship existed between percent metaphyton cover in the littoral zone and the percent of land use in agriculture. Metaphyton abundance is impacted by land use practices and subsequent loss of nutrients from the catchment.     

Watershed Management Technique to Control Sediment Yield in Agriculturally Dominated Areas

Abstract

Non-point source pollution is recognized internationally as a critical environmental problem. In Illinois, soil erosion from agricultural lands is the major source of such pollution. The erosion process, which has been accelerated by human activity, tends to reduce crop productivity and leads to subsequent problems from deposition on farmlands and in water bodies. Comprehensive watershed management, however, can be used to protect these natural resources. In this study, a discrete time optimal control methodology and computational model are developed for determining land use and management alternatives that minimize sediment yield from agriculturally-dominated watersheds. The solution methodology is based on an interface between a genetic algorithm and the U.S. Department of Agriculture's Soil and Water Assessment Tool. Model analyses are performed on a farm field basis to allow capture of different, local stakeholder perspectives, and crop management alternatives are based on a three-year rotation pattern. The decision support tool is applied to the Big Creek watershed located in the Cache River basin of Southern Illinois. The application demonstrates that the methodology is a valuable tool in advancing comprehensive watershed management. The study represents part of an ongoing research effort to develop an even more comprehensive decision support tool that uses multi-criteria evaluation to address social, economic, and hydrologic issues for integrative watershed management.     

Dynamics of wet‐season turbidity in relation to precipitation,discharge, and land cover in three urbanizing watersheds,Oregon

Frequent intense precipitation events can mobilize and carry sediment and pollutants into rivers, degrading water quality. However, how seasonal rainfall and land cover affect the complex relationship between discharge and turbidity in urban watersheds is still under investigation. Using hourly discharge, rainfall, and turbidity data collected from six stations in three adjacent watersheds between 2008 and 2017, we examined the temporal variability of the discharge–turbidity relationship along an urban–rural gradient. We quantified hysteresis between normalized discharge and turbidity by a hysteresis index and classified hysteresis loops during 377 storm events in early, mid, and late wet season. Hysteresis loop index and direction varied by site land cover type and season. Turbidity values peaked quicker in the watersheds with higher degrees of urban development than in a less urbanized watershed. The positive relation between discharge and turbidity was highest in two downstream stations in the mid wet season, whereas it was highest in two upstream stations in the early wet season. Correlation and regression analysis showed that maximum turbidity was best explained by discharge range, and the sensitivity of turbidity to discharge change was higher in the larger downstream watershed than in the small upstream watersheds. A flashiness index was negatively associated with the slope of turbidity versus discharge, suggesting that turbidity is difficult to predict solely on the basis of discharge in flashy urban streams. This paper contributes to a deeper understanding of the spatial and temporal variation of discharge–concentration relationship in urbanizing watersheds, which can help water managers increase the resiliency of water‐related ecosystem services to impacts of climate change.     

基于试验流域的季风区洪水特性及其水文模拟

根据我国安徽省5个试验流域的实测资料,分析了各流域场次洪水的特性,并利用TOPMODEL模型对各流域进行次洪模拟,进一步探讨该模型在我国东部季风区洪水预报方面的适用性。结果表明:安徽省各试验流域场次洪水的降雨量-径流深散点均呈现较好的正相关性,降雨量随着海拔的升高而增大,山区的径流系数大于平原丘陵区;面积最小的瓦屋刘流域对暴雨的响应最为敏感,孙村流域场次洪水的洪峰模数差异最小、起涨时间最长,黄山流域场次洪水的历时最久;随着海拔的升高,流域地形指数的平均值逐渐增大,同时各流域面积占比最大所对应的地形指数逐渐减小;地形指数标准差越大的流域,土地利用类型也越丰富;TOPMODEL模型总体上可以较好地模拟安徽省各试验流域场次洪水过程,且对大流量的捕捉效果优于小流量,对天然流域的模拟效果优于人类活动扰动的流域。     

Modeling the effects of climate change on different land uses.

This study deals with the effects of the expected climate change on the hydrology of watersheds. The watershed response in terms of the water produced by the watershed has been modeled using HSPF (Hydrological Simulation Program-FORTRAN) for a time period which encompasses the first half of the twenty-first century. Climate change scenarios have been prepared based on trends expected in western Turkey and a hypothetical watershed with different land uses has been simulated. The trends have been extracted from the results of a general circulation model. The simulations have revealed that watersheds with no vegetative cover will respond to the trends in temperature and precipitation more rigorously than vegetated watersheds. Pasture or watersheds with deciduous or coniferous forests respond less to climate change due to the buffering mechanism of the vegetative cover and also due to the large quantities of water they transpire. It has also been found that monthly variations are important in predicting the future response of watersheds. While changes might seem small on a yearly scale, there are large differences in response among seasons.     

Finite Element Method and GIS Based Distributed Model for Soil Erosion and Sediment Yield in a Watershed

The objective of this study is to develop a soil erosion and sediment yield model based on the kinematic wave approximation using the finite element method, remote sensing and geographical information system (GIS) for calculating the soil erosion and sediment yield in a watershed. Detachment of soil particles by overland flow occurs when the shear stress at the surface overcomes the gravitational forces and cohesive forces on the particles. Deposition occurs when the sediment load is greater than the transport capacity. Beasley et al.’s (Trans ASAE 23:938–944, 1980) transport equations for laminar and turbulent flow conditions are used to calculate the transport capacity. The model is capable of handling distributed information about land use, slope, soil and Manning’s roughness. The model is applied to the Catsop watershed in the Netherlands and the Harsul watershed in India. Remotely sensed data has been used to extract land use/land cover map of the Harsul watershed, and other thematic maps are generated using the GIS. The simulated results for both calibration and validation events are compared with the observed data for the watersheds and found to be reasonable. Statistical evaluation of model performance has been carried out. Further, a sensitivity analysis has also been carried out to study the effect of variation in model parameter values on computed volume of sediment, peak sediment and the time to peak sediment. Sensitivity analysis has also been carried out for grid size variation and time step variation of the Catsop watershed. The proposed model is useful in predicting the hydrographs and sedigraphs in the agricultural watersheds.     

基于相似流域法的SWAT模型模拟黄河中游无资料地区径流

选用黄河中游两个小流域,基于相似流域法探求分布式水文模型SWAT在黄河中游小流域无资料地区径流模拟的适用性。通过距离、流域面积相近及属性相似的方法,用已知流域率定参数移植到无资料流域进行径流模拟。选取2009-2013年的日径流与月径流进行模型率定,以效率系数(NS)和决定系数(R2)为评价指标,率定出4个模型敏感系数,并用2014-2016年的日径流与月径流进行模型验证。结果显示:率定期月径流模拟的R2为0. 76,NS为0. 70;日径流模拟的R2为0. 70,NS为0. 64;验证期月径流模拟的R2为0. 82,NS为0. 74;日径流模拟的R2为0. 78,NS为0. 68。说明基于相似流域法的SWAT模型对于无资料的小流域月径流量模拟具有很好的适用性。     

Landscape-scale modeling of water quality in Lake Superior and Lake Michigan watersheds: How useful are forest-based indicators?

The Great Lakes watersheds have an important influence on the water quality of the nearshore environment, therefore, watershed characteristics can be used to predict what will be observed in the streams. We used novel landscape information describing the forest cover change, along with forest census data and established land cover data to predict total phosphorus and turbidity in Great Lakes streams. In Lake Superior, we modeled increased phosphorus as a function of the increase in the proportion of persisting forest, forest disturbed during 2000–2009, and agricultural land, and we modeled increased turbidity as a function of the increase in the proportion of persisting forest, forest disturbed during 2000–2009, agricultural land, and urban land. In Lake Michigan, we modeled increased phosphorus as a function of ecoregion, decrease in the proportion of forest disturbed during 1984–1999 and watershed storage, and increase in the proportion of urban land, and we modeled increased turbidity as a function of ecoregion, increase in the proportion of forest disturbed during 2000–2009, and decrease in the proportion softwood forest. We used these relationships to identify priority areas for restoration in the Lake Superior basin in the southwestern watersheds, and in west central and southwest watersheds of the Lake Michigan basin. We then used the models to estimate water quality in watersheds without observed instream data to prioritize those areas for management. Prioritizing watersheds will aid effective management of the Great Lakes watershed and result in efficient use of restoration funds, which will lead to improved nearshore water quality.