Hydrograph Separation by Incorporating Climatological Factors: Application to Small Experimental Watersheds 1

Abstract: Evaluating the relative amounts of water moving through the different components of the hydrological cycle is required for precise management and planning of water resources. An important aspect of this evaluation is the partitioning of streamflow into surface (quick flow) and base‐flow components. A prior study evaluated 40 different approaches for hydrograph‐partitioning on a field scale watershed in the Coastal Plain of the Southeastern United States and concluded that the Boughton’s method produced the most consistent and accurate results. However, its accuracy depends upon the proper estimation of: (1) the end of surface runoff, and (2) the fraction factor (α) that is function of many physical and hydrologic characteristics of a watershed. Proper identification of the end of surface runoff was accomplished by using a second derivative approach. Applying this approach to 12 years of separately measured surface and subsurface flow data from a field scale watershed (study area) proved to be accurate for 87% of the time. Estimation of the α value was accomplished in this study using two steps: (1) alpha was fitted to individual hydrographs: and, (2) a regression equation that determines these alpha values based on climatological factors (e.g., rainfall, evapotranspiration) was developed. Using these strategies improved the streamflow partitioning method’s performance significantly.     

南京近50年冬季低温冰冻积雪事件的气候特征

应用南京逐日观测资料分析了南京低温、冰冻和积雪灾害的变化特征及其与区域气候变暖的联系,得到如下结论:①低温、冰冻、积雪事件都存在一定的年代际和年际的周期变化;冬季平均最低气温和极端最低气温具有相似的周期性特征;积雪深度的年代际尺度的周期特征明显,但是较小尺度的年际周期不明显;②近50年来南京的低温、冰冻、积雪事件呈现波动下降的趋势;③南京年均气温和低温、冰冻、积雪事件之间存在较强的相关性与区域气候变暖关系密切。     

不同利用方式下黄壤旱坡地磷素状况及环境影响分析

通过对贵州黄壤进行采样以及采用无界径流小区法收集地表径流,探索不同利用方式下黄壤旱坡地磷素水平及其地表径流磷浓度的差异。结果表明,不同利用方式下黄壤旱坡地中全磷和有效磷(Olsen-P)含量的大小顺序为连作烟地>烤烟-玉米轮作地>连作玉米地>林地;CaCl_2浸提磷(土壤易解吸磷)和Na0H浸提磷(藻类可利用的土壤总磷)与土壤全磷和有效磷有显著的相关性;土壤富磷化的同时,其磷素的流失风险明显地提高。连作烟地地表径流总磷(TP)和磷酸根态磷(Ortho-P)浓度明显大于连作玉米地.而林地地表径流TP浓度明显小于旱地;黄壤旱坡地地表径流中TP和Ortho-P与土壤有效磷之间存在极显著的相关性(r为0.957、0.875),因而连作烟地磷素的环境影响潜能明显高于其它旱地以及林地。     

水库中长期径流预报系统的开发研究

水库中长期径流预报系统采用PowerBuilder作为系统主要开发工具，集水情信息查询、检索、监视、预报与管理等功能于一体，实现了中长期水文预报和信息管理的各种功能要求。该系统具有功能全面，技术基础坚实，通用性和开放性强，自动化程度高，界面友好，全菜单操作等特点。     

Ecological responses to variation in seasonal snow cover

Seasonal snow is among the most important factors governing the ecology of many terrestrial ecosystems, but rising global temperatures are changing snow regimes and driving widespread declines in the depth and duration of snow cover. Loss of the insulating snow layer will fundamentally change the environment. Understanding how individuals, populations, and communities respond to different snow conditions is thus essential for predicting and managing future ecosystem change. We synthesized 365 studies that examined ecological responses to variation in winter snow conditions. This research encompasses a broad range of methods (experimental manipulations, measurement of natural snow gradients, and long-term monitoring), locations (35 countries), study organisms (plants, mammals, arthropods, birds, fish, lichen, and fungi), and response measures. Earlier snowmelt was consistently associated with advanced spring phenology in plants, mammals, and arthropods. Reduced snow depth often increased mortality or physical injury in plants, although there were few clear effects on animals. Neither snow depth nor snowmelt timing had clear or consistent directional effects on body size of animals or biomass of plants. However, because 96% of studies were from the northern hemisphere, the generality of these trends across ecosystems and localities is also unclear. We identified substantial research gaps for several taxonomic groups and response types; research on wintertime responses was notably scarce. Future research should prioritize examination of the mechanisms underlying responses to changing snow conditions and the consequences of those responses for seasonally snow-covered ecosystems.     

北京市大气颗粒物PM2.5,PM10及降雪中的汞

研究了北京大气颗粒物PM25,PM10及降雪中的汞.结果表明,北京大气颗粒物PM25中汞的浓度为024—179ng·m-3,PM10中汞的浓度为038—302ng·m-3,冬季PM25和PM10中汞的浓度明显高于夏季;北京大气可吸入颗粒物中的汞均以细粒子(≤25μm)为主,冬季细粒子中汞的浓度高是细粒子多且其汞含量高共同作用的结果,而夏季则是细粒子中汞的含量高.降雪中汞的浓度在106—162ng·l-1之间,降雪中可溶性汞为总汞的一半左右.     

建筑垃圾对雨水径流中Cu的吸附特性

以砖混建筑垃圾为研究对象,采用人工模拟雨水,通过静态和动态吸附实验研究了不同粒径粒级建筑垃圾对雨水径流中Cu的吸附效果。结果表明,准二级动力学模型比准一级动力学模型能更好地描述建筑垃圾对Cu的吸附过程;Freundlich等温模型能较好地拟合其等温吸附过程;不同粒径粒级建筑垃圾均对雨水径流中的Cu具有较好的净化效果,去除率均超过90%,粒径粒级越小,对Cu的净化效果越好,但其渗透性能越差;建筑垃圾的粒径粒级对Cu的吸附平衡时间、吸附速率和吸附量具有重要影响,粒径粒级2.36~4.75 mm的建筑垃圾对Cu的平衡吸附速率和平衡吸附量最大,分别为4.1 μg/min 和12.4 μg/g。     

ROLE OF EROSION PROCESSES IN TRANSFER OF RADIONUCLIDES: RESULTS OF FIELD EXPERIMENTS1

ABSTRACT: An experimental one-year fieldwork has been conducted in the vicinity of the Chernobyl NPP, within an agricultural watershed, to study the transfer of radionuclides brought into the environment by the disaster of 1986. Presented are results of observation of the washout of ¹³⁷Cs from the runoff plot both in natural conditions and under artificial rainfalls. Beside traditional hydro-logical methods, new techniques were used allowing to consider microtopographical peculiarities of the runoff plot and their role in the redistribution of radionuclides. The estimate of the annual mass balance for the soil and the radionuclides within the runoff plot has shown that, regardless of significant areal variation of their concentration, the ¹³⁷Cs washout with the solid runoff resulted from artificial rainfalls amounts to some 1 percent of its reserves in the uppermost 5 cm of the topsoil. The same parameter for the natural runoff is lower by an order of magnitude. Both these factors of self-purification are about two times less than natural radioactive decay of ¹³⁷Cs.     

EFFECTS OF CLIMATE CHANGE ON HYDROLOGY AND WATER RESOURCES IN THE COLUMBIA RIVER BASIN1

ABSTRACT: As part of the National Assessment of Climate Change, the implications of future climate predictions derived from four global climate models (GCMs) were used to evaluate possible future changes to Pacific Northwest climate, the surface water response of the Columbia River basin, and the ability of the Columbia River reservoir system to meet regional water resources objectives. Two representative GCM simulations from the Hadley Centre (HC) and Max Planck Institute (MPI) were selected from a group of GCM simulations made available via the National Assessment for climate change. From these simulations, quasi-stationary, decadal mean temperature and precipitation changes were used to perturb historical records of precipitation and temperature data to create inferred conditions for 2025, 2045, and 2095. These perturbed records, which represent future climate in the experiments, were used to drive a macro-scale hydrology model of the Columbia River at 1/8 degree resolution. The altered streamflows simulated for each scenario were, in turn, used to drive a reservoir model, from which the ability of the system to meet water resources objectives was determined relative to a simulated hydrologic base case (current climate). Although the two GCM simulations showed somewhat different seasonal patterns for temperature change, in general the simulations show reasonably consistent basin average increases in temperature of about 1.8–2.1°C for 2025, and about 2.3–2.9°C for 2045. The HC simulations predict an annual average temperature increase of about 4.5°C for 2095. Changes in basin averaged winter precipitation range from -1 percent to + 20 percent for the HC and MPI scenarios, and summer precipitation is also variously affected. These changes in climate result in significant increases in winter runoff volumes due to increased winter precipitation and warmer winter temperatures, with resulting reductions in snowpack. Average March 1 basin average snow water equivalents are 75 to 85 percent of the base case for 2025, and 55 to 65 percent of the base case by 2045. By 2045 the reduced snowpack and earlier snow melt, coupled with higher evapotranspiration in early summer, would lead to earlier spring peak flows and reduced runoff volumes from April-September ranging from about 75 percent to 90 percent of the base case. Annual runoff volumes range from 85 percent to 110 percent of the base case in the simulations for 2045. These changes in streamflow create increased competition for water during the spring, summer, and early fall between non-firm energy production, irrigation, instream flow, and recreation. Flood control effectiveness is moderately reduced for most of the scenarios examined, and desirable navigation conditions on the Snake are generally enhanced or unchanged. Current levels of winter-dominated firm energy production are only significantly impacted for the MPI 2045 simulations.     

RUNOFF RESPONSE FROM TWO RECLAIMED WATERSHEDS1

ABSTRACT: Detailed studies of the surface hydrology of reclaimed surface-mined watersheds for both rainfall and snowmelt events are non-existent for central Alberta yet this information is crucial for design of runoff conveyance and storage structures. A study was initiated in 1992 with principal objectives of quantifying surface runoff for both summer rainfall and spring snowmelt events and identifying the dominant flow processes occurring in two reclaimed watersheds. Snowmelt accounted for 86 and 100% of annual watershed runoff in 1993 and 1994, respectively. The highest instantaneous peak flow was recorded during a summer rainfall event with a return period of greater than 50 years. Infiltration-excess overland flow was identified as the dominant flow process occurring within the Sandy Subsoil Watershed, whereas saturation overland flow was the principal runoff process occurring within the West Watershed.