基于SCS和GIS的不同降雨情景城市内涝过程模拟方法

针对城市暴雨内涝灾害频发的现状,基于城市暴雨强度公式、芝加哥降雨过程线模型、SCS(Soil Conservation Service)产流模型以及基于地理信息系统软件ArcGIS的局部等体积法,提出一种关于城市暴雨内涝过程的模拟方法。选取武汉市内涝灾害严重的汤逊湖流域作为研究对象,使用该方法对流域内多种重现期暴雨内涝量的积水高程和积水淹没范围进行模拟。结果表明:汤逊湖流域内产生的内涝较为严重,10 a一遇的暴雨即可对低洼地区造成轻微内涝;不同重现期暴雨产生的积水区域基本是一致的,但重现期越长的暴雨产生的积水高程越深,淹没范围越广,对周边造成的影响越大。该研究成果对城市暴雨内涝的预防与治理具有借鉴和参考价值。     

太湖和洪泽湖天然有机质与重金属结合特性研究

利用同步荧光光谱表征浅水湖泊太湖和洪泽湖中天然有机质(NOM)的组成,同时利用荧光淬灭滴定试验研究了NOM与Cu~(2+)和Cd~(2+)的结合特性。结果表明:两个湖泊的NOM中类蛋白质和类腐殖质组成比例存在显著的差异,太湖NOM主要由类蛋白质和类腐殖质组成,洪泽湖NOM则以类腐殖质为主;太湖和洪泽湖NOM与Cu~(2+)和Cd~(2+)的结合点位及结合能力存在显著差异,NOM中类腐殖质的结合点位要显著多于类蛋白质;太湖贡湖湾和梅梁湾NOM中类蛋白质与Cu~(2+)的结合能力以及梅梁湾NOM中类蛋白质与Cd~(2+)的结合能力强于类腐殖质,但贡湖湾NOM中类蛋白质与Cd~(2+)的结合能力则弱于类腐殖质,而洪泽湖NOM中类蛋白质与Cu~(2+)和Cd~(2+)的结合能力均强于类腐殖质;太湖NOM与重金属Cu~(2+)和Cd~(2+)的结合能力要显著高于洪泽湖NOM。     

长江鄱阳湖问题的原因及湖口建闸的影响

根据实际资料分析了近年鄱阳湖环境面貌剧烈变化的原因和湖口建闸的影响,结果表明:当前鄱阳湖汛后提前干枯主要是长江上游水库群改变了河川径流节律,减少汛后水量,使河湖提前入枯和河道大幅冲刷,全线汛后水位平均降低2～4 m(湖口2.76 m),径流减少是主要原因;鄱阳湖大量采砂已经破坏了入江水道的自然水力顶托机制,使枯季(2—3月)湖区(都昌)平均水位降低2 m,这是鄱阳湖连续出现极低水位的原因;鄱阳湖流域水库拦截和长江汛期洪水减少、湖水位降低和持水量减少等,也使近年8—10月湖口入湖和出湖流量大幅度减少,加剧了湖区汛后水位降低,特别是鄱阳湖七河尾闾干旱。上述变化已经对湖区生态环境和周边生产生活影响很大,但鄱阳湖基本自然特征没有改变。湖口建闸是可控制湖区汛后水位消落和抬高枯水位,但是建闸隔断江湖,对洄游鱼类生存、鸟类生境和湖区环境影响很大;长江受三峡大坝隔断后,再在湖口建闸将严重肢解流域自然生态系统,使长江生境多样性彻底丧失;而且建闸还将进一步加剧长江下游水位降低,改变河湖面貌,降低环境容量和河口抵御咸潮能力。解决鄱阳湖问题应该在长江流域层面统筹寻找对策,建议严格坚持三峡工程规划确定的主要防大洪水原则,适当调整流域总体规划,提高湖区流域水利工程调节能力和增加汛后补水,修复鄱阳湖入江水道,加强鄱阳湖及周边适应能力建设等。     

Optical scattering properties of organic-rich and inorganic-rich particles in inland waters

We present the results from a study of the particulate scattering properties of three bodies of water that represent a wide range of optical properties found in inland waters. We found a positive linear relationship (R² = 0.45, P < 0.005) between the mass-specific scattering coefficient at 532 nm (b_p*(532)) and the ratio of the inorganic suspended material (ISM) to the total suspended material (TSM) in our study areas. In contrast to earlier studies in which b_p*(532) was lower for inorganic particles than for organic particles, we found that the value of b_p*(532) for ISM (b_p*(532)_ISM = 0.71 m²/g) was approximately 1.6 times greater than the value found for organic suspended materials (OSM) (b_p*(532)_OSM = 0.45 m²/g). We found that the dependence of the particle scattering coefficient (b_p) on wavelength (λ) could be described accurately by a power law (with mean average percent error (MAPE) < 0.07) in waters dominated by inorganic particles. The model errors in waters dominated by organic particles, however, were much larger (MAPE > 0.1), especially in the spectral region associated with strong phytoplankton absorption. The errors could be reduced over this wavelength range by adding a term to the model to account for particle absorption, but the additional term tended to increase the error outside of this range. We conclude that information about the nature of the scattering particles in lake waters is necessary for the selection of an appropriate model for particle absorption and that a hybrid model that includes absorption over some wavelength ranges may be necessary.     

Hydrology influences generalist–specialist bird-based indices of biotic integrity in Great Lakes coastal wetlands

Marsh bird habitats are influenced by water levels which may pose challenges for interpreting bird-based indices of wetland health. We determined how much fluctuating water levels and associated changes in emergent vegetation influence the Index of Marsh Bird Community Integrity (IMBCI) using data collected in Great Lakes coastal wetlands by participants in Bird Studies Canada's Great Lakes Marsh Monitoring Program. IMBCI scores for 90 wetlands in Lake Erie and 131 wetlands in Lake Ontario decreased with decreasing water levels due to decreasing number of marsh-dependent species in Lake Erie and perhaps also in Lake Ontario. The average magnitude of the decrease in scores between extremely high and low water periods for wetlands with sufficient data was 15% in Lake Erie where water dropped 0.9 m on average (n = 11 wetlands) and 18% in Lake Ontario where water dropped 0.5 m (n = 7). Scores in Lake Erie increased with increasing Typha due to increasing numbers of marsh-dependent species and decreased with increasing Phragmites due to increasing numbers of generalist species. The opposite was observed in Lake Ontario, perhaps due to denser Typha and sparser Phragmites. Scores were explained by the naturally fluctuating water levels of Lake Erie, which favored Phragmites expansion and the regulated water levels of Lake Ontario which promoted Typha expansion. Scores were influenced by fluctuating water levels and associated changes in emergent vegetation. Inter-annual water level fluctuations should be considered when interpreting any indicator of wetland health that is based on marsh-dependent bird species.     

河道湖泊地形的数字重构研究

以鄱阳湖实测地形散点、河道大断面及SRTM基础数据,结合遥感图像判断河道主流线、滩槽分界线,开发了由CAD格式河道大断面线性数据提取河道高程结点并转化为含地理信息高程结点的算法。采用正交网格曲线插值算法完成了河道断面曲面内插高程结点,重构了鄱阳湖流域湖泊及河道的数字地形。重构后的地形数据与实测数据相比较在河槽高程、形态及面积吻合较好;能满足在数字地球模型上进行三维仿真的需要,表明该方法的具有可行性和实用性。     

Condition of resident fish communities in the Eighteenmile Creek Area of Concern,New York

The lower 3.5 km of Eighteenmile Creek, a tributary to Lake Ontario in New York, was designated as an Area of Concern (AOC) in 1985 under the Great Lakes Water Quality Agreement due to extensive contamination of bed sediments by polychlorinated biphenyls (PCBs) and other toxicants. Five beneficial use impairments (BUIs) have been identified in this AOC, including degraded fish and wildlife populations. We surveyed fish communities in the Eighteenmile Creek AOC and in a comparable section of a nearby reference stream (Oak Orchard Creek) during June 2019 to infer whether legacy contaminants are currently impairing fish communities in the AOC to an extent that they differ from the regional reference condition. Estimates of community abundance, biomass, diversity, and fish condition from each system were compared using a noninferiority testing framework. Biomass, diversity, and fish condition in the Eighteenmile Creek AOC were similar or superior to that in Oak Orchard Creek, while abundance was 20% lower in the AOC. These findings and those of a 2007 sampling effort suggest that fish communities in the Eighteenmile Creek AOC are not impaired despite recent studies indicating that PCBs are bioaccumulating in fish tissues at 1–2 orders of magnitude above background levels. Future assessments in the Eighteenmile Creek AOC might focus on the condition of benthic macroinvertebrate communities and potential toxicity of local contaminants to piscivorous wildlife in order to fully address the remaining aspects of the fish and wildlife populations beneficial use impairment.     

Modelling of nearshore microbial water quality at confluence of a local tributary in Lake St. Clair

Microbial water quality, measured as Escherichia coli (E. coli) concentration, at beaches along the southern shore of Lake St. Clair in Canada, often exceeds public safety guidelines. Belle River, located near a public beach and a drinking water intake, is one of the several smaller tributaries of the lake whose contribution to nearshore microbial water quality is currently unknown. A flexible mesh 3D coupled TUFLOW-FV and Aquatic Ecodynamic (AED2+) model was used to simulate the hydrodynamics and microbial water quality in Lake St. Clair. A higher resolution nested model was developed within the lake-wide TUFLOW-FV model for better spatial and temporal resolution in the local region surrounding Belle River. Regular and up to a factor of four difference in predicted E. coli concentrations were observed with the nested and lake-wide models at the public beach next to Belle River, whereas the difference was marginal at the drinking water intake about a kilometre away from the shore. While the E. coli loading to Lake St. Clair from Belle River is considered negligible, >90% of the predicted daily E. coli concentration at the beach and > 50 % at the water intake were attributed to Belle River from amongst all watershed sources to Lake St. Clair considered in the model. The model results also show that the construction of a new 150 m jetty in 2018, replacing the older 25 m jetty separating Belle River from the public beach, is expected to significantly reduce E. coli concentrations observed at the beach.     

Contemporary spatial extent and environmental drivers of larval coregonine distributions across Lake Ontario

Coregonine fishes are important to Laurentian Great Lakes food webs and fisheries and are central to basin-wide conservation initiatives. In Lake Ontario, binational management objectives include conserving and restoring spawning stocks of cisco (Coregonus artedi) and lake whitefish (C. clupeaformis), but the spatial extent of contemporary coregonine spawning habitat and the environmental factors regulating early life success are not well characterized. In Spring 2018, we conducted a binational ichthyoplankton assessment to describe the spatial extent of coregonine spawning habitat across Lake Ontario. We then quantified the relative importance of a suite of biophysical variables hypothesized to influence coregonine early life success using generalized additive mixed models and multimodel inference. Between April 10 and May 14, we conducted 1,092 ichthyoplankton tows and captured 2,350+ coregonine larvae across 17 sampling areas, predominantly within embayments. Although 95% of catches were in the eastern basin, coregonine larvae were also found in historical south shore spawning areas. Most coregonine larvae were cisco; <6% were lake whitefish. Observed catches of both species across sampling areas were strongly and similarly associated with ice cover duration, but the importance of site-specific characteristics varied, such as distance to shore and site depth for cisco and lake whitefish, respectively. These results suggest that regional-scale climatic drivers and local environmental habitat characteristics interact to regulate early life stage success. Furthermore, strong regional and cross-species variation in larval distributions emphasize the importance of lake-wide assessments for monitoring both the current eastern basin populations and potential expansions into western Lake Ontario habitats.     

Coupled modelling of storm surge,circulation and surface waves in a large stratified lake

The wind-driven nature of large lakes suggests that the accuracy of meteorological inputs is essential for hydrodynamic modelling. Moreover, coupling between the meteorological inputs and density stratification may also influence the simulated lake behavior. To investigate wind-driven large lake processes, a high-resolution coupled Delft3D-SWAN model was applied to Lake Ontario to simulate storm surges, surface waves, and circulation during two recent storm events. In both events, the sustained wind speeds approached 20 m s^?1; however, variations in wind direction and duration altered the lake's surface wave and storm surge responses. The influence of different atmospheric inputs was investigated by comparing results from two spatially varied atmospheric models: the Rapid Refresh (RAP) and the High-Resolution Deterministic Prediction System (HRDPS). Hydrodynamic simulations using HRDPS were marginally better, with maximum root mean squared errors (RMSE) between modelled and observed water levels of 0.07 m, compared to 0.08 m with RAP. Predictions of the magnitude and timing of the maximum wave heights varied based on wind fields, with differences between predicted peak wave heights of up to 0.4 m. Both events occurred during a stratified period, allowing for a comparative evaluation of the influence of baroclinic and barotropic processes on the simulated surface wave and storm surge results. Simulations including the vertical density gradient gave a better representation of current velocities with depth and resulted in an improved prediction of peak storm surge magnitudes and surface water level behavior following the storms, reducing the RMSE by up to 12%.