高原湖泊旅游资源的生态可持续利用评价研究

本文以旅游资源的生态可持续利用为目标,结合高原湖泊旅游资源的特性,提出了湖泊旅游资源可持续利用评价指标体系,建立了综合评价的多目标、线性加权函数模型,并利用此模型,对抚仙湖进行了实证研究,评价方法具有可操作性和一定的推广价值.     

CONCEPTUAL DESIGN PROCEDURE FOR HYDRAULIC DESTRATIFICATION SYSTEMS IN SMALL PONDS,LAKES, OR RESERVOIRS FOR WATER QUALITY IMPROVEMENT1

ABSTRACT: Forced artificial mixing of temperature-stratified ponds, or small lakes or reservoirs, by liquid jets can enhance water quality and can also be energy efficient. Based on previous studies of jet mixing mechanics of stratified water bodies, a conceptual design approach is presented. The main “operational” and “system” design parameters are considered in the proposed method. Using minimization of a total cost estimate as a criterion, an iterative method for the selection of the number and size of the jets is developed and illustrated.     

COMPARATIVE WATER CHEMISTRY OF FOUR LAKES IN ROCKY MOUNTAIN NATIONAL PARK1

ABSTRACT: The inorganic chemistry of two pairs of lakes in Rocky Mountain National Park was studied to determine reasons for their similarities and differences. The pairs were located on differing geologic units. It was expected that weathering from the different types of parent material would cause differing cation concentrations between the pairs. This was verified by dissimilar concentrations of those cations which are products of primary weathering. Unexpected was a significant difference in anion concentrations between members of one pair having the same bedrock geology. This difference has been attributed to the presence of a wet sedge meadow above one of the lakes which serves as a biological filter for anions, particularly nitrate and sulfate. It is shown that small scale drainage characteristics which can alter regional atmospheric contributions are important contributors to lake chemistry.     

The Great Lake’s future at a cross road

Some argue that a collective vision for the future of the Laurentian Great Lakes is embodied in the␣Great Lakes Water Quality Agreement (GLWQA). The GLWQA is a binational agreement, first signed in 1972 by Prime Minister Pierre Trudeau and President Richard Nixon, wherein the two countries (the Parties) commit to “restore and maintain the chemical, physical and biological integrity of the waters of the Great Lakes Basin Ecosystem.” Article X of the Agreement states that the Parties shall conduct a comprehensive review of the operation and effectiveness of this Agreement following every third biennial report of the [International Joint] Commission (IJC). The IJC’s 12th Biennial Report, released in 2004, triggered this important science, program, and policy review which commenced May 2006. This essay makes the case for a rigorous review, that explores deliberately the future scope of the Agreement to protect the world’s largest surface freshwater resource, and calls for innovation in the governance regime of this binational ecosystem.     

RESPONSE OF NORTH AMERICAN FRESHWATER LAKES TO SIMULATED FUTURE CLIMATES1

ABSTRACT: We apply a physically based lake model to assess the response of North American lakes to future climate conditions as portrayed by the transient trace-gas simulations conducted with the Max Planck Institute (ECHAM4) and the Canadian Climate Center (CGCM1) atmosphere-ocean general circulation models (A/OGCMs). To quantify spatial patterns of lake responses (temperature, mixing, ice cover, evaporation) we ran the lake model for theoretical lakes of specified area, depth, and transparency over a uniformly spaced (50 km) grid. The simulations were conducted for two 10-year periods that represent present climatic conditions and those around the time of CO₂ doubling. Although the climate model output produces simulated lake responses that differ in specific regional details, there is broad agreement with regard to the direction and area of change. In particular, lake temperatures are generally warmer in the future as a result of warmer climatic conditions and a substantial loss (> 100 days/yr) of winter ice cover. Simulated summer lake temperatures are higher than 30°C over the Midwest and south, suggesting the potential for future disturbance of existing aquatic ecosystems. Overall increases in lake evaporation combine with disparate changes in A/OGCM precipitation to produce future changes in net moisture (precipitation minus evaporation) that are of less fidelity than those of lake temperature.     

宁武亚高山湖泊细菌群落的时空格局及驱动机制

受人类活动和气候变化的影响,亚高山湖泊生态系统日趋退化,导致微生物群落生物多样性和结构改变.本研究以宁武亚高山湖泊公海(GH)水体细菌群落为研究对象,通过Q-PCR和DGGE技术分析了不同季节和不同深度的水体中细菌群落多样性分布格局,探究细菌群落的时空动态及其多样性维持机制.结果表明,温度(T)、酸碱度(p H)、溶解氧(DO)、电导率(EC)、盐度(SAL)和铵态氮(NH4+)在每个月的不同采样深度间均有显著差异.细菌群落丰度具有明显的时空动态,其中8月的丰度最高,11月最低;在水体中层(2、4和6 m)的丰度较高,表层和底层(0 m和8 m)相对较低.细菌群落α多样性指数在各月份和不同深度间均有显著性差异,从4～12月整体上呈现先减少后增加的趋势.相似性分析(PERMANOVA)结果表明,不同深度之间细菌群落的空间分布格局明显不同(P 0. 001).冗余分析(RDA)和方差分解(VPA)结果表明在不同深度下,细菌群落多样性格局是环境选择和扩散限制共同作用的结果,但是环境选择的相对作用更强,其中水体无机氮(NO3-、NO2-和NH4+)浓度是主要的影响因子.总之,宁武亚高山湖泊公海中细菌群落多样性有明显的时空分布格局,环境选择作为主要因素驱动了细菌群落的多样性格局.     

Exploratory Analysis of the Winter Chemistry of Five Lakes on the North Slope of Alaska1

Abstract: Lakes are important water resources on the North Slope of Alaska. Freshwater is required for oilfield production as well as exploration, which occurs largely on ice roads and pads. Since most North Slope lakes are shallow, the quantity and quality of the water under ice at the end of winter are important environmental management issues. Currently, water‐use permits are a function of the presence of overwintering fish populations, and their sensitivity to low oxygen concentrations. Sampling of five North Slope lakes during the winter of 2004‐2005 shed some light on the winter chemistry of four lakes that were used as water supplies and one undisturbed lake. Field analysis was conducted for oxygen, conductivity, pH, and temperature throughout the lake depth, as well as ice thickness and water depth. Water samples were retrieved from the lakes and analyzed for Na, Ca, K, Mg, Fe, dissolved‐organic carbon, and alkalinity in the laboratory. Lake properties, rather than pumping, were the best predictors of oxygen depletion, with the highest dissolved‐oxygen levels maintained in the lake with the lowest concentration of constituents. Volume weighted mean dissolved‐oxygen concentrations ranged from 4 to 94% of saturation in March. Dissolved oxygen and specific conductance data suggested that the lakes began to refresh in May.     

Long term changes in the eutrophication process in a shallow Mediterranean lake ecosystem of W. Greece: response after the reduction of external load

Lake Pamvotis is a shallow Mediterranean lake located in Western Greece near the city of Ioannina. The lake has been recognized as an internationally important conservation site under European Community legislation due to its rich biodiversity. However, during the last three decades the trophic status of the lake has changed as a result of anthropogenic activity (among others irrigation and domestic sewage discharge), resulting in serious problems. Here we present data about the long-term development in eutrophication of Lake Pamvotis. Water samples were collected and analyzed (water temperature, pH, dissolved oxygen, nutrients, chlorophyll-a) during three monitoring periods: 1985-1989, 1998-1999, 2004-2005. The high nutrient concentrations in the lake water during the three monitoring periods, as well as its eutrophic to hypertrophic status reflect the degree of impact anthropogenic activity has had on the lake. Commencement of a restoration plan in 1995-1996, involving sewage diversion, led to a reduction in external nutrient load and consequently to lower in-lake nutrients and Chlorophyll-a concentrations. Orthophosphate concentration decreased by about 87%, nitrates fell below 1.20mg/l, whilst the total reduction of inorganic N compounds showed a weaker downward trend, fluctuating between 0.39 and 1.24mg N/l with an average value of 0.76mg N/l. However, after a short-term recovery the eutrophic status of the lake remains eight years later (2004-2005), suggesting the importance of the internal loading process and the absence of the top-down effect of fish. This study provides evidence for the need of greater restoration efforts utilized in Mediterranean shallow lakes.     

Arctic Lake Physical Processes and Regimes with Implications for Winter Water Availability and Management in the National Petroleum Reserve Alaska

Lakes are dominant landforms in the National Petroleum Reserve Alaska (NPRA) as well as important social and ecological resources. Of recent importance is the management of these freshwater ecosystems because lakes deeper than maximum ice thickness provide an important and often sole source of liquid water for aquatic biota, villages, and industry during winter. To better understand seasonal and annual hydrodynamics in the context of lake morphometry, we analyzed lakes in two adjacent areas where winter water use is expected to increase in the near future because of industrial expansion. Landsat Thematic Mapper and Enhanced Thematic Mapper Plus imagery acquired between 1985 and 2007 were analyzed and compared with climate data to understand interannual variability. Measured changes in lake area extent varied by 0.6% and were significantly correlated to total precipitation in the preceding 12 months (p < 0.05). Using this relation, the modeled lake area extent from 1985 to 2007 showed no long-term trends. In addition, high-resolution aerial photography, bathymetric surveys, water-level monitoring, and lake-ice thickness measurements and growth models were used to better understand seasonal hydrodynamics, surface area-to-volume relations, winter water availability, and more permanent changes related to geomorphic change. Together, these results describe how lakes vary seasonally and annually in two critical areas of the NPRA and provide simple models to help better predict variation in lake-water supply. Our findings suggest that both overestimation and underestimation of actual available winter water volume may occur regularly, and this understanding may help better inform management strategies as future resource use expands in the NPRA.     

Temporal and Spatial Trends in Nutrient and Sediment Loading to Lake Tahoe,California‐Nevada,USA

Since 1980, the Lake Tahoe Interagency Monitoring Program (LTIMP) has provided stream‐discharge and water quality data—nitrogen (N), phosphorus (P), and suspended sediment—at more than 20 stations in Lake Tahoe Basin streams. To characterize the temporal and spatial patterns in nutrient and sediment loading to the lake, and improve the usefulness of the program and the existing database, we have (1) identified and corrected for sources of bias in the water quality database; (2) generated synthetic datasets for sediments and nutrients, and resampled to compare the accuracy and precision of different load calculation models; (3) using the best models, recalculated total annual loads over the period of record; (4) regressed total loads against total annual and annual maximum daily discharge, and tested for time trends in the residuals; (5) compared loads for different forms of N and P; and (6) tested constituent loads against land use‐land cover (LULC) variables using multiple regression. The results show (1) N and P loads are dominated by organic N and particulate P; (2) there are significant long‐term downward trends in some constituent loads of some streams; and (3) anthropogenic impervious surface is the most important LULC variable influencing water quality in basin streams. Many of our recommendations for changes in water quality monitoring and load calculation methods have been adopted by the LTIMP.