Salmonid observations at a Klamath River thermal refuge under various hydrological and meteorological conditions

The Beaver Creek confluence with the main‐stem Klamath River was studied to assess salmonid use in a thermal mixing zone under various summer hydrological and meteorological conditions. Main‐stem flow releases from Iron Gate Dam ranged from 17 cms (615 cfs) to 37 cms (1320 cfs) during the study period and main‐stem water temperatures ranged from 19.5 to 26°C. A grid was constructed to define the thermal refuge as a system of cells. Temperatures were monitored using remote temperature loggers and fish counts were conducted using daytime snorkelling. Most juvenile salmonids were observed moving into the refuge when main‐stem temperatures exceeded 22–23°C. Salmonids in the thermal refuge did not necessarily seek the coolest water, but were generally located in habitats commensurate with species‐specific behavioural needs within their thermal tolerance range. Such ranges largely occurred within refuge areas. Variable meteorological conditions confounded observable biological thermal benefit to fish resulting from higher or lower main‐stem flows. Thermal regime dynamics indicated that under the hydrological and meteorological conditions observed, higher flows from Iron Gate Dam showed some ability to change the structure of the refuge area. It appeared that without the thermal refuge, main‐stem flows alone could not sustain the salmonid population because high water temperatures usually exceeded their published thermal tolerance limits. Copyright © 2007 John Wiley & Sons, Ltd.     

太平溪小流域水土保持蓄水减沙效益初步研究

太平溪小流域地处三峡库乎宜昌县西部，距三峡坝５ｋｍ的长江西陵峡北岸，治理前水土流失严重，大量坡面商沙以沟道推移直接进入三峡库区。     

Snowpack response in the Assiniboine-Red River basin associated with projected global warming of 1.0 °C to 3.0 °C

This study assesses snow response in the Assiniboine-Red River basin, located in the Lake Winnipeg watershed, due to anthropogenic climate change. We use a process-based distributed snow model driven by an ensemble of eight statistically downscaled global climate models (GCMs) to project future changes under policy-relevant global mean temperature (GMT) increases of 1.0 °C to 3.0 °C above the pre-industrial period. Results indicate that basin scale seasonal warmings generally exceed the GMT increases, with greater warming in winter months. The majority of GCMs project wetter winters and springs, and drier summers, while autumn could become either drier or wetter. An analysis of snow water equivalent (SWE) responses under GMT changes reveal higher correlations of snow cover duration (SCD), snowmelt rate, maximum SWE (SWE_max) and timing of SWE_max with winter and spring temperatures compared to precipitation, implying that these variables are predominantly temperature controlled. Consequently, under the GMT increases from 1.0 °C to 3.0 °C, the basin will experience successively shorter SCD, slower snowmelt, smaller monthly SWE and SWE_max, earlier SWE_max, and a transition from snow-dominated to rain-snow hybrid regime. Further, while the winter precipitation increases for some GCMs compensate the temperature-driven changes in SWE, the increases for most GCMs occur as rainfall, thus limiting the positive contribution to snow storage. Overall, this study provides a detailed diagnosis of the snow regime changes under the policy-relevant GMT changes, and a basis for further investigations on water quantity and quality changes.     

Towards improving an Area of Concern: Main-channel habitat rehabilitation priorities for the Maumee River

The Maumee River watershed in the Laurentian Great Lakes Basin has been impacted by decades of pollution and habitat modification due to human settlement and development. As such, the lower 35 km of the Maumee River and several smaller adjacent watersheds comprising over 2000 km² were designated the Maumee Area of Concern (AOC) under the revised Great Lakes Water Quality Agreement in 1987. As part of pre-rehabilitation assessments in the Maumee AOC, we assessed fish and invertebrate communities in river km 24–11 of the Maumee River to identify: 1) areas that exhibit the highest biodiversity, 2) habitat characteristics associated with high biodiversity areas, 3) areas in need of protection from further degradation, and 4) areas that could feasibly be rehabilitated to increase biodiversity. Based on benthic trawl data, shallow water habitats surrounding large island complexes had the highest fish diversity and catch per unit effort (CPUE). Electrofishing displayed similar fish diversity and CPUE patterns across habitat types early in the study but yielded no discernable fish diversity or CPUE patterns towards the end of our study. Although highly variable among study sites, macroinvertebrate density was greatest in shallow water habitats <2.5 m and around large island complexes. Our results provide valuable baseline data that could act as a foundation for developing rehabilitation strategies in the lower Maumee River and for assessing the effectiveness of future aquatic habitat rehabilitation projects. In addition to increasing in-channel habitat, watershed-scale improvements of water quality might be necessary to ensure rehabilitation strategies are successful.     

长江科学院野外科学观测与科学考察回顾及展望

野外科学观测与科学考察既是基础性科技工作,又是自主创新突破口。近年来,长江科学院设立了野外科学观测中心,初步形成覆盖长江流域,涵盖生态、环境、资源及灾害防治等领域的野外科学观测研究站网体系,持续开展长江流域野外科学观测和多专业综合性科学考察。回顾了长江科学院野外科学观测和科学考察的发展历程,从基础条件、观测成果、科技支撑、骨干队伍以及社会影响等方面,系统总结了长江科学院在野外科学观测与科学考察方面取得的成绩。未来将着重做好基础设施建设、长期观测与考察、科学研究与示范、合作交流以及人才队伍建设等方面工作,以期为长江流域高质量发展提供支撑。     

长江上游高洪水期泥沙输移特性

长江上游高洪水期(汛期)泥沙输移特性是决定三峡库区泥沙淤积的关键因素,直接关乎三峡水库使用寿命及综合效益的发挥。借助干、支流长系列水沙资料,分析了长江三峡水库入库寸滩站高洪水期泥沙输移特性,结果表明:近40 a来,寸滩站场次洪水中7 d洪量未出现趋势性变化,而7 d沙量显著减少,高洪水期输沙经历了“涨水输沙占优—涨、落水基本持平—落水输沙占优”的变化过程。2013年以前,寸滩站高洪水期径流及泥沙均主要来自于金沙江,而向家坝、溪洛渡水电站陆续投运后,2013—2019年寸滩站洪水场次(洪峰流量30 000 m³/s以上)共计14场。从径流来源来看,仅4场主要来自于金沙江,其余9场主要来自于嘉陵江,1场来自岷江;从泥沙来源来看,9场主要来自于嘉陵江,其余5场分别来自于沱江、岷江、横江,金沙江已不是寸滩站高洪水期过程中泥沙的主要来源区。研究成果可为三峡水库沙峰排沙调度、库尾减淤调度提供理论支撑,为长江泥沙治理提供保障。     

黄河淤积粉土的两种复合稳定方案与性能对比

为探索路基工程中黄河淤积粉土的稳定技术和性能保障方案,针对德州齐河县境内的黄河淤积粉土,在乳化沥青复合稳定粉土(AE稳定土)的研究基础上,采用无机/有机复合材料制备出一种复合固化剂(FG固化剂),研究了AE稳定土和FG稳定土2种稳定方案下粉土的抗压强度性质、水稳定性和抗冻融能力;结合XRD、SEM表征技术,探讨了FG固化剂的稳定机理。研究认为,FG固化剂稳定土较AE稳定土有着更高的无侧限抗压强度、回弹模量和承载能力,水稳定性良好,在抗冻融能力上有着比AE稳定土更好的效果。XRD与SEM分析表明,FG固化剂提供了活性矿物质,其复合胶凝效应和填充增强保障了粉土的抗压强度,高分子物质起到粘结颗粒界面、填塞孔隙的作用,降低了内部孔隙率;两者造成土体的最大干密度变大;与AE稳定土的稳定机理不同。FG固化剂的使用为黄河粉土的稳定和工程应用提供了参考方法。     

广东省东江流域显著水问题类型识别

通过构建流域水资源、水环境与水生态功能评价指标体系,采用ArcGIS自然间断点分级法分析广东省东江流域水资源、水环境与水生态3类涉水功能的空间格局特征,采用Spearman等级相关系数定量分析3类涉水功能间的交互作用,识别各地区显著水问题类型,并提出相应管控策略。结果表明：广东省东江流域水资源、水环境与水生态功能评价等级空间格局体现出显著的空间差异性;流域水资源、水环境与水生态功能间的交互作用类型为兼容;基于3类涉水功能评价等级及功能间交互作用类型,将广东省东江流域10个评价单元划分为水资源、水环境、水生态、水资源-水环境、水生态-水环境及非显著型6个显著水问题类型。