Presentation and analysis of a model simulating epilimnetic and hypolimnetic temperatures in lakes

An important factor in aquatic modelling is water temperature. This is especially true for dimictic lakes where stratification and mixing influence many processes and variables, such as oxygen conditions, lake water retention time, etc. This paper evaluates and improves an existing method to predict water temperatures developed by Håkanson ,1996 (Ecol. Model., 88:157–181). The method is incorporated in a model simulating water temperatures in epilimnion and hypolimnion. The model is calibrated and validated against an extensive set of empirical data. It is driven by readily available parameters, e.g. latitude, continentality and altitude. The predictive power, especially for the epilimnetic temperature, is such that the model could be used as a sub-model in many models concerning lake ecosystems. However, the model has only been tested for Swedish lakes covering a relatively narrow range in terms of latitude, longitude and altitude and it would be interesting to investigate if this approach also holds for other parts of the world. As an example of how the model can be used in practise, a simulation of retention of caesium in lake water, using the temperature model as a sub-model, is presented.     

江汉湖区的开发及其环境效应

江汉湖区位于长江中游的湖北省东南部,是中国湖泊密集度最大的淡水湖群区,也是重要的农业生产基地。本文从历史的角度分析了江汉平原湖区的开发及其环境２。江汉湖区全面开发始于南宋,至明清进入第一高潮,从那时起,人类驿湖区环境的影响越来越大,近年来尤为突出,主要表现为：（）砍伐森林,致使水土流失加重,河湖中的泥沙含量增加;（２）围湖垦殖,导致湖泊萎缩,降低了其对洪水的调蓄能力,生态环境不断恶化：（３）修筑提     

可持续发展：西部大开发的基本理念

本文从西部大开发的深远意义出发 ,探讨西部大开发的约束条件 ,进而讨论可持续发展是西部大开发的基本理念 ,并以可持续发展为指导原则提出建议。     

Toward an improved ecosystem based management approach: incorporating catchment characteristics into better management and planning of the Great Barrier Reef marine ecosystem

Discharge from the Great Barrier Reef Catchment (GBRC) is considered the second most serious threat to the Great Barrier Reef, Australia. Utilising principal component analysis (PCA) and cluster analysis (CA), this research aimed to assess the variability and co-variation of 28 water basins (WBs) within the GBRC, in order to improve the institutional arrangements and regulation of water quality and increase collaboration horizontally between management organisations, and vertically between government tiers. Water basin variability was measured by nine variables: size (ha), population, agricultural land use (ha), number of major water storages, major rivers and major towns, total nitrogen exported (T/yr), total phosphorus exported (T/yr) and herbicide use (ha). The Fitzroy WB, with PC scores of 7.0081, 2.2897 and ?1.6504, was identified as the most dissimilar and therefore needing to be managed differently. Many WBs within the same regions were very dissimilar to each other, indicating that current management practices, based largely on geographic location, are unlikely to be the most efficient and effective. Instead, managing groups of WBs with similar geo-political properties (determined by the CA) could be more effective and efficient. Coordination and collaboration are key to successful ecosystem based management, therefore managing similar WBs together through inter-NRM (natural resource management) agreements, irrespective of their geographical location, facilitates management bodies building strong, cooperative working relationships.     

巢湖水资源开发和水环境保护

巢湖是我国五大淡水湖之一,也是安徽省最大淡水湖,对安徽省的工农业生产和人民生活起着举足轻重的作用。本文分析了对巢湖水资源开发中产生的主要环境问题,并提出了在保护生态环境的前提下开发巢湖水资源的战略措施。     

EVALUATION OF GREAT LAKES NET BASIN SUPPLY FORECASTS1

ABSTRACT: Evaluation of the Great Lakes Environmental Research Laboratory's (GLERL's) physically-based monthly net basin supply forecast method reveals component errors and the effects of model improvements for use on the Laurentian Great Lakes. While designed for probabilistic outlooks, it is assessed for giving deterministic outlooks along with other net basin supply forecast methods of the U.S. Army Corps of Engineers and Environment Canada, and with a stochastic approach commissioned by the Corps. The methods are compared to a simple clima-tological forecast and to actual time series of net basin supplies. Aetual net basin supplies are currently determined by estimating all components directly, instead of as water-balance residuals. This is judged more accurate and appropriate for both forecasting and simulation. GLERL's physically-based method forecasts component supplies while the other methods are based on residual supplies. These other methods should be rederived to be based on component supplies. For each of these other methods, differences between their outlooks and residual supplies are used as error estimates for the rederived methods and component supplies. The evaluations are made over a recent period of record high levels followed by a record drought. Net basin supply outlooks are better than climatology, and GLERL's physically-based method performs best with regard to either component or residual net basin supplies. Until advances are made in long-range climate outlooks, deterministic supply outlooks cannot be improved significantly.     

Zinc and lead sequestration in an impacted wetland system

The fate and bioavailability of pollutant metals is important to the long-term health of freshwater wetland systems, particularly in areas with elevated background levels of trace metals. Precipitation of some authigenic mineral phases in wetland sediments can potentially limit metal bioavailability through sequestration in low-solubility compounds, such as metal sulfides. Zinc and Pb concentrations were analyzed in water, plant and sediment samples taken from a metal-contaminated wetland in Chicago, IL, USA in order to assess metal fate and bioavailability, while X-ray absorption spectroscopy (XAS) studies were conducted to determine zinc speciation in the wetland sediments. The results showed sequestration of metal into the pond sediments, most likely in iron precipitate phases. In surface sediments, re-release of Zn and Pb into pore waters was correlated with microbial iron reduction, while the presence of sulfide in anoxic pore waters corresponded to decreased dissolved concentrations of both elements. Analysis of extended X-ray absorption fine structure (EXAFS) data confirmed that sulfide compounds dominated zinc speciation throughout the sediment. Uptake of trace metals in Phragmites plants was limited primarily to plant roots, while concentrations of both Pb and Zn in aquatic vegetation were significantly elevated, representing a potential bioaccumulation hazard.     

Environmentally stratified sampling design for the development of Great Lakes environmental indicators

Understanding the relationship between human disturbance and ecological response is essential to the process of indicator development. For large-scale observational studies, sites should be selected across gradients of anthropogenic stress, but such gradients are often unknown for a population of sites prior to site selection. Stress data available from public sources can be used in a geographic information system (GIS) to partially characterize environmental conditions for large geographic areas without visiting the sites. We divided the U.S. Great Lakes coastal region into 762 units consisting of a shoreline reach and drainage-shed and then summarized over 200 environmental variables in seven categories for the units using a GIS. Redundancy within the categories of environmental variables was reduced using principal components analysis. Environmental strata were generated from cluster analysis using principal component scores as input. To protect against site selection bias, sites were selected in random order from clusters. The site selection process allowed us to exclude sites that were inaccessible and was shown to successfully distribute sites across the range of environmental variation in our GIS data. This design has broad applicability when the goal is to develop ecological indicators using observational data from large-scale surveys.