Lakes & Reservoirs: Science, Policy and Management for Sustainable Use

Nweze, Nkechinyere O.

doi: 10.1111/j.1440-1770.2006.00292.xpmid: N/A

Water samples were collected on a monthly basis at three locations along the north–south axis of the lake at 1 m depth intervals for 1 year. A sedimentation technique was used for microscopic examination of the samples. The monthly mean and seasonal phytoplankton densities were calculated. The original data were square‐root transformed, and analysis of variance performed with SPSS version 10.0. The significant treatment effects were determined using Fisher's least significance difference at the 5% probability level. The mean phytoplankton population per millilitre was very high for the entire sampling period. There was a phytoplankton bloom formation in the early rainy season, with the mean total phytoplankton population density for the rainy season (April–October) being significantly higher than that of for the dry season (November–March). A population increase was observed during the late part of the dry season to the early part of the rainy season. During the rainy season, Chlorophyceae (mostly desmids) were most abundant, followed by Cyanobacteria, Bacillariophyceae, Euglenophyceae, Dinophyceae, Cryptophyceae, Chrysophyceae and Xanthophyceae, in decreasing order of abundance. This order changed slightly in the dry season, when there was relative abundance of Bacillariophyceae over Cyanophyceae, and Dinophyceae over Euglenophyceae. The low population of Euglenophyceae indicates that the organic pollution is still low, with the predominance of desmids, indicating an oligotrophic lake condition.

Awulachew, Seleshi Bekele

doi: 10.1111/j.1440-1770.2006.00293.xpmid: N/A

There is few available information regarding the water resource systems of Abaya Lake and Chamo Lake, which are found in the Southern Rift Valley Region of Ethiopia. This paper describes modelling of the water balance components of these lakes, as well as the impacts of water uses, and sediment transport and deposition in the lakes. The various parameters and data needed for the water balance model are derived on the basis of various surveys, analysis of data and modelling efforts. The watershed characteristics are derived using geographical information system, whereas the morphometry of the lakes is investigated by undertaking bathymetry surveys. The hydrometeorological components of this lake system also were investigated through the development of relevant database and information systems, by identifying regional relationships, and by a rainfall‐run‐off model. These information systems have subsequently been integrated to model the water balance of the two lakes, and simulating the in‐lake water levels. Several scenarios reflecting the natural conditions, water consumptive development possibilities, and sedimentation impacts have been investigated in this study. Based on the model simulation results, and on the computation of the life expectancies of the two lakes, it was found that sediment inflow and deposition significantly threaten their existence.

Tüzün, İlhami; İnce, Özlem

doi: 10.1111/j.1440-1770.2006.00298.xpmid: N/A

The effects of water inflow–outflow volumes on the in‐lake total phosphorus (TP) concentrations was investigated for the deep, stratified Çubuk II Dam Lake. The fluctuations in the TP concentrations followed a seasonal pattern, with lower values found during the summer, and peak values during wet seasons. Both the seasonal pattern and the horizontal/vertical heterogeneities in the TP concentrations were usually found to be in accordance with those of the water flow parameters. The vertical differences in the TP concentrations provided evidence that an interflow formed at the 5 m and 10 m depths by the water inflow resulted in higher mean TP concentrations at these depths. In contrast, the water outflows had a reducing effect on the TP concentrations, particularly at the 15 m depth, by promoting net TP export. Although the horizontal distribution of the TP concentrations differed slightly between the riverine, transition and lacustrine zones, the differences did not indicate any statistical significance (P > 0.05, multivariate analysis of variance). The path analysis performed on the vertical data proved to be a promising tool in estimating the direct correlations between water flow dynamics and TP concentrations when the decomposition of indirect correlations via dissolved oxygen concentrations and temperature was accounted for in these mutual associations.

Sekino, Tatsuki; Nakamura, Masahisa

doi: 10.1111/j.1440-1770.2006.00295.xpmid: N/A

Although environmental management projects typically must collect large quantities of data and information from a variety of related fields, these data and information often are not used effectively. In this study, an experimental version of a knowledge management system (Learning Acceleration and Knowledge Enhancement System) was developed to solve problems related to the acquisition and accumulation of large quantities of information being applied to an international project on lake management. Two functions were incorporated in the system, including (i) a function for previewing retrieved documents so that the information obtained using a specific search word could be easily accessed; and (ii) a thesaurus function to facilitate the sourcing and understanding by decision‐makers and other stakeholders of information in unfamiliar, but related, fields of study. As these functions enable users to search for data and information in fields that might be unfamiliar to them, the application of knowledge management to projects involving environmental issues can be a valuable tool for such projects in the future.

Jørgensen, S. E.

doi: 10.1111/j.1440-1770.2006.00296.xpmid: N/A

The Ecological Engineering and Ecosystem Restoration previously presented 19 ecological principles that can be used for all ecotechnological projects. This report discusses how all projects that incorporate or involve engineering and management of ecosystems should be guided by these previously noted ecological principles. The principles also can be used as a checklist for ensuring that all relevant ecological considerations are taken into account in the development and implementation of ecotechnology and ecological management projects. This report demonstrates how these 19 principles can be applied in lake management issues. It is shown that the principles also are useful as a checklist for lake management efforts. This report further identifies general and 12 specific recommendations for lake management efforts, which are based on the 19 principles.

Oberholster, P. J.; Botha, A.‐M.; Cloete, T. E.

doi: 10.1111/j.1440-1770.2006.00297.xpmid: N/A

One of the most severe problems associated with eutrophication of urban freshwater ecosystems is the occurrence of increasingly frequent blooms of toxic cyanobacteria. Cyanotoxins might accumulate in the trophic web, producing diverse intoxication symptoms and chronic effects that are difficult to diagnose and prevent. High mortality of domestic animals and fish has been reported previously under these prevailing conditions. This study investigates the taxonomic composition of phytoplankton assemblages in Sheldon Lake during the summer of 2004, a year after the completion of a restoration project on the lake. The study analysed the physical and chemical changes caused by urban run‐off and artificial mixing, as well as the usefulness of microcystin molecular markers derived from the mcy gene cluster for the detection of toxic cyanobacterial strains in environmental samples from Sheldon Lake. This study clearly demonstrates that the artificial mixing rate alone was insufficient to cause a transition to a well‐mixed aquatic system, and that cyanobacteria remained dominant throughout the summer months. The presence of toxic cyanobacterial strains was confirmed with the use of molecular markers that detected the presence of the mcy gene cluster responsible for the production of toxin by Microcystis spp. This approach might have a great potential use in the routine analyses of urban aquatic ecosystems. It also might make toxicity monitoring more feasible, allowing for the early application of corrective actions, especially for cases such as Sheldon Lake, which is a public recreational focal point.

Al‐Jassabi, S.; Khalil, A. M.

doi: 10.1111/j.1440-1770.2006.00294.xpmid: N/A

The cyanobacteria Microcystis aeruginosa forms extensive summer blooms in the King Talal Reservoir, the largest water body in Jordan. The occurrence of the blooms is a function of the water temperature, light intensity and nutrient concentration, with the nitrogen and phosphorus levels being critical factors. This initial study indicated that the time of the seasonal maximum and intensity of Microcystis blooms in the King Talal Reservoir vary significantly from month to month, with a peak reached in summer. The low nutrient concentrations were observed prior to the summer season. There was a rapid, extensive proliferation of M. aeruginosa during the summer of the same year, especially from 1–30 June to 30 November. The LD50 of microcystin in Balb/c was found to be 50 µL kg−1. Additional studies will provide further information on various aspects of the identification and toxicity of the selected cyanobacterial species.