Bottomfast Ice Mapping and the Measurement of Ice Thickness on Tundra Lakes Using C‐Band Synthetic Aperture Radar Remote Sensing1

Abstract: Industrial activity in Canada’s north is increasing, placing demands on the use of water from lakes to build ice roads. Winter water withdrawal from these lakes has the potential to impact overwintering fish. Removal of water from small lakes can decrease oxygen and habitat available to fish. To address this issue, a protocol has been developed by the Department of Fisheries and Oceans outlining water withdrawal thresholds. Bathymetric surveys are the traditional method to determine lake depth, but are costly given the remoteness of northern lakes. This paper investigates the use of satellite C‐band synthetic aperture radar (SAR) remote sensing technology as a potential alternative or complement to traditional survey methods. Previous research has shown that a SAR can detect the transition from grounded to floating ice on lakes, or if a lake is completely frozen. Grounded ice has a dark signature while floating ice appears very bright in contrast. Similar results were observed for the datasets acquired in the study area. This suggests that lakes that freeze completely to the bottom can be identified using SAR. Such water bodies would not be viable fish overwintering habitat and can therefore be used as water sources without thresholds necessary. However, attempts to accurately calculate the depth of the ice at the grounded‐floating ice boundary using bathymetric profiles acquired in the summer and lake ice thickness measurements from a reference lake near Inuvik proved to be unreliable.     

A Review of Water Level Fluctuations on Aquatic Biota With an Emphasis on Fishes in Ice‐Covered Lakes1

Abstract: The effects of water level fluctuations on fish and other aquatic biota, with an emphasis on winter water withdrawal in northern regions is reviewed. Water demands for population growth and development are adding pressure on water reserves, particularly when coupled with changing climatic conditions. Water level fluctuations can have adverse effects on the environment, most notably to hydrologic and biotic processes ranging in magnitude from the micro‐scale to landscape level. Water level management of lakes and reservoirs can affect all forms of aquatic biota. The severity of effect is dependant on the magnitude, duration and timing of the fluctuation, and the species exposed. In northwestern Canada and northern Alaska, water is withdrawn from water bodies to construct ice‐roads and other winter based developments. Biota in small, isolated water bodies are particularly sensitive to reductions in winter water levels. Water withdrawals can reduce the oxygen available to overwintering fish, while reduced water levels can reduce habitat for fish and furbearers, and freeze littoral areas killing plants, invertebrates, and fish eggs. Regulatory winter water withdrawal thresholds have been developed in the Northwest Territories and Alaska and continue to be refined as new data becomes available. The use of thresholds can help minimize or avoid negative impacts to the environment, particularly fish, from winter water withdrawal activities. Many different factors may influence the effect that winter water withdrawal has on a water body, such as basin shape, substrate and location. More research is warranted to better understand the linkages between anthropogenic and natural water level fluctuations and their combined effect on aquatic ecosystems. A general decision support system is proposed for minimizing risk to aquatic life from winter water withdrawal activities.     

北京城市河湖营养状态与蓝藻水华研究

2003-2004年的调研结果显示,北京城市河湖(长河水系)总氮平均含量为1.667 mg/L,总磷平均含量为0.144 mg/L,浮游藻类平均细胞密度为41 150×104/L,其中蓝藻占90.0%.浮游藻类的群落结构为蓝藻(Cyanophyta)-绿藻(Chlorophyta)型,河湖水体中营养盐与初级生产力的关系为浮游藻类响应型,连续两年发生以微囊藻(Microcystis)占优势的蓝藻水华.河湖水体5项指标(SD、TP、TN、CODMn、Chla)的TSIM值在57～87间,水体已达到富营养或重富营养程度.其主要原因是:1)营养盐和有机物的污染;2)北京市淡水资源紧缺,补给城市河湖水量少;3)在河湖水系治理中,底部硬化,两侧(或周围)衬砌,破坏了水体的自然生态系统,使其自净能力大大降低.     

Exploration of relationships between phytoplankton biomass and related environmental variables using multivariate statistic analysis in a eutrophic shallow lake： A S-year study

Understanding the process of the changing phytoplankton patterns can be particularly useful in water quality improvement and management decisions. However, it is generally not easy to illustrate the interactions between phytoplankton biomass and related environmental variables given their high spatial and temporal heterogeneity. To elucidate relationships between them, in a eutrophic shallow lake, Taihu Lake, relative long-term data set of biotic and abiotic parameters of water quality in the lake were conducted using multivariate statistical analysis within seasonal periodicity. The results indicate that water temperature and total phosphorus （TP） played governing roles in phytoplankton dynamics in most seasons （i.e. temperature in winter, spring and summer; TP in spring, summer and autumn）; COD （chemical oxygen demand） and BOD （biological oxygen demand） presented significant positive relationships with phytoplankton biomass in spring, summer and autumn. However, a complex interplay was found between phytoplankton biomass and nitrogen considering significant positive relationships occurring between them in spring and autumn, and conversely negative ones in summer. As the predatory factor, zooplankton presented significant grazing-pressure on phytoplankton biomass during summer in view of negative relationship between them in the season. Significant feedback effects of phytoplankton development were identified in summer and autumn in view that significant relationships were obser,qed between phytoplankton biomass and pH, Trans （transparency of water） and DO. The results indicate that interactions between phyto：plankton biomass and related environmental variables are highly sensitive to seasonal periodicity, which improves understanding of different roles of biotic and abiotic variables upon phytoplankton variability, and hence, advances management methods for eutrophic lakes.     

枯水年长江中下游江湖水交换作用分析

利用宜昌、汉口、大通、城陵矶、湖口等重要水文站的长时间序列水位、流量资料,着重分析了1978年和2006年典型枯水年长江中下游江湖水交换作用。论文建立了能表明江湖水交换作用的经验公式,以此为量化方法来表示江湖水交换作用的强度。结果表明:1978年代表三峡大坝建造之前典型枯水年的性质,2006年则已显示出三峡水库的运行对通江湖泊与干流水交换的积极作用。表现在江湖水交换系数上,1978年洞庭湖和鄱阳湖分别为0.57和0.56,洞庭湖和鄱阳湖与长江水交换处于稳定状态;2006年洞庭湖和鄱阳湖水交换系数分别为0.89和0.51,显示出2006年比1978年水交换作用强烈。洞庭湖和鄱阳湖与长江交换水量显示:1978年补给长江水量为分别为1 990×10⁸ m³和947×10⁸ m³,约占同期大通径流量的29%和14%;2006年补给长江水量分别为1 962×10⁸ m³和1 564×10⁸ m³,约占同期大通径流量的28%和23%。尤其是2006年鄱阳湖补水量比平水年还多5%,该年大通站流量全年维持在10 000 m³/s以上,以此保证了下游乃至河口地区水资源供给的安全。     

厦门周边水库浮游植物碱性磷酸酶活性研究

从2010年6月初至12月末,对厦门周边九龙江江东水库、厦门大学芙蓉湖和情人湖三个淡水湖库进行两周一次的连续采样,开展水体总碱性磷酸酶活性(APA)的研究。从营养盐和叶绿素a水平看,三个湖库属不同的富营养化程度:芙蓉湖>情人湖>江东水库。群落水平的总碱性磷酸酶活性和溶解性磷酸盐(SRP)浓度的结果表明,三处水体均呈现群落水平上的磷胁迫状态;不同水体的浮游植物群落结构存在显著差异,同时不同浮游植物的磷胁迫亦不同,蓝藻是芙蓉湖的绝对优势类群且标记率较低,绿藻是情人湖和江东水库的优势类群,且标记率较高。群落组成在一定程度上可以反映浮游植物群落的磷胁迫状态。     

高原湖泊周边浅层地下水:磷素时空分布及驱动因素

高原湖泊周边农田磷肥的大量施用和城镇村落的聚集造成了土壤剖面磷素不断累积和含磷污染物的大量排放,加剧了湖泊周边浅层地下水的磷污染,磷随湖泊周边区域浅层地下径流入湖也影响着高原湖泊的水质安全. 2019～2021年雨季和旱季,通过对云南8个湖泊周边农田和居民区水井进行监测,分析了452个浅层地下水样中磷浓度的时空差异及驱动因素.结果表明,季节变化和土地利用影响了浅层地下水中磷浓度及其组成,表现为雨季浅层地下水中磷浓度大于旱季,农田大于居民区;溶解性总磷(DTP)是总磷(TP)的主要形态,占75%～81%,溶解性无机磷(DIP)是DTP的主要形态,占74%～80%.8个湖泊周边近30%的样本TP浓度已超过地表水Ⅲ水标准(GB 3838),其中,洱海(52%)、杞麓湖(45%)、星云湖(42%)和滇池(29%)湖泊周边地下水磷的超标率远高于阳宗海(16%)、抚仙湖(13%)、程海(6%)和异龙湖(5%).影响浅层地下水磷浓度的关键因子是土壤剖面中水溶性磷(WEP)、含水率(MWC)、土壤有机质(SOM)、总氮(TN)、 pH和浅层地下水中pH、水位(P<0.05).土壤WEP、 SOM...     

云南九大高原湖泊治理的复杂性、艰巨性和长期性

详细分析了云南省九大高原湖泊治理的复杂性、艰巨性和长期性。     

苏州平原河网区浅水湖泊冬夏季浮游植物群落与环境因子的典范对应分析

2005年12月和2006年6月对苏州平原河网区57个浅水湖泊的浮游植物群落进行了调查,共检出浮游植物8门62属73种,浮游植物主要由绿藻、硅藻和蓝藻组成.冬季浮游植物平均丰度为254.88×10⁴cells·L^-1,硅藻门丰度占总丰度的62.3％;夏季浮游植物平均丰度为2 704.28×10⁴cells·L^-1,蓝藻门丰度达93.5％.运用典范对应分析(canonical correspondence analysis, CCA)对调查范围内的57个样点62属浮游植物与11个环境因子关系进行研究.结果表明,水温、高锰酸盐指数、NO^-₃-N和TN是影响苏州平原河网区浅水湖泊浮游植物群落分布的主要环境因子,在冬季,pH、NH⁺₄-N及TP也是主要的影响因子;浮游植物中硅藻对环境变化具有较强的适应性,绿藻能耐受较高的高锰酸盐指数、氮磷营养盐和TOC浓度,而蓝藻对环境因子的响应有待进一步的研究.     

洞庭湖区典型内湖表层沉积物中氮、磷和重金属空间分布与污染风险评价

为了解洞庭湖区内湖表层沉积物中氮、磷和重金属污染空间分布及其生态风险,分别对南湖、黄盖湖、冶湖、鹤龙湖、洋沙湖、湘阴东湖、华容东湖等7个内湖进行现场调查及表层沉积物采样,采用主成分分析法、相关分析法分析了氮、磷和重金属的来源,同时运用综合污染指数法（FF）、地积累指数法（I_geo）与潜在生态风险指数法（RI）评价内湖的污染现状及其生态风险.结果表明:①南湖w（TN）高于洞庭湖区土壤背景值,累积倍数为0.03倍;华容东湖、南湖、冶湖、湘阴东湖、洋沙湖、黄盖湖w（TP）均高于洞庭湖区土壤背景值,累积倍数分别为1.94、1.63、0.84、0.53、0.28、0.26倍;各内湖中w（Cd）、w（Hg）、w（Cu）、w（Pb）、w（Cr）、w（Zn）、w（Ni）均高于洞庭湖沉积物背景值,累积倍数平均值分别为1.09、2.29、1.24、1.62、0.66、0.44、1.78倍.②主成分分析与相关性分析表明,第1主成分TN、Cu、Cr、Ni的质量分数主要受农业生产及养殖业影响,第2主成分Cd、Hg、Pb、Zn的质量分数受工业活动影响最大,第3主成分TP、As、Sb的质量分数主要受生活污染影响.③综合污染指数表明,南湖表层沉积物氮、磷面临重度污染,华容东湖、黄盖湖面临中度污染,湘阴东湖、鹤龙湖、洋沙湖面临轻度污染.④地积累指数表明,南湖表层沉积物重金属面临严重污染,黄盖湖、鹤龙湖面临重污染,湘阴东湖、华容东湖、冶湖面临偏中度污染,洋沙湖面临轻度污染.⑤潜在生态风险指数表明,南湖、湘阴东湖表层沉积物重金属面临较高风险,其余5个内湖面临中等风险.研究显示,洞庭湖区内湖表层沉积物不同程度受氮、磷及重金属污染,南湖综合污染尤为严重,内源污染应引起重视.