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No description available.

No description available.

No description available.

No description available.

A general survey was carried out on the sediments of seventeen lakes, ranging from oligotrophic to eutrophic, in the English Lake District. Several variables not directly concerned with the population of bacteria were measured to provide background information. Estimates of the total population of bacteria and of the population of filamentous bacteria were made using direct counts with acridine orange and fluorescein di-acetate, and counts by an MPN technique. The counts with acridine orange showed an upward trend with increasing degree of enrichment of the lakes, particularly at the eutrophic end of the spectrum. The distribution pattern obtained with the fluorochrome fluorescein di-acetate was different with an apparent upward trend in the intermediate lakes. The viable counts of the bacterial population in the sediments did not agree with the ranking of the lakes according to published information from the Freshwater Biological Association, although a slight upward trend was observed in the distribution of the viable filamentous bacteria. The preliminary survey led to the selection of three lakes representing the oligrotrophic, mesotrophic and eutrophic states in which a more detailed investigation on the population of filamentous bacteria was made. The profundal and littoral zones of the three lakes were investigated particularly in relation to the different groups of filamentous bacteria and their vertical distribution in the sediments. The groups of filamentous bacteria were described based on morphological and cytochemical tests. A tentative key for identification of filamentous bacteria was devised.

<p> The coupling of the stream tracer technique with transient storage modeling is a well-established approach to characterizing solute transport processes of complex stream systems. Stream tracer studies require a large number of samples and the associated chemical analyses are costly. Sampling and analytical demand would be significantly reduced if electrical conductivity - a robust, easy-to-measure, water-quality property- was used as the primary measure of tracer breakthrough and converted to bromide tracer concentrations for breakthrough curve analysis and transient storage model parameter optimization. The advantages of collecting electrical conductivity data as a surrogate for dissolved bromide tracer samples are (1) reduced cost of laboratory analysis, (2) high-frequency data collection by field instruments, and (3) well-defined breakthrough curves for enhanced transient storage model simulations.</p><p> This method was tested by collecting electrical conductivity data and dissolved tracer samples during an instantaneous sodium bromide (NaBr) injection experiment in Fourmile Creek, Boulder County, Colorado. Concentrations of bromide were calculated from electrical conductivity data using equations that relate electrical conductivity of natural waters to their chemical composition. Models of transient storage were simulated for both the tracer data derived from electrical conductivity and the measured tracer data.</p><p> Small changes in background electrical conductivity caused the highest error (%) in the breakthrough curves. The method was robust in stream reaches where changes in background electrical conductivity could be accounted for. The use of high-frequency calculated bromide data within the transient storage model provided improved parameter estimates.</p>

An evaluation has been carried out of the groundwater system in Bahrain. It has involved the collection of water samples from all the water bearing formations to study the quality of the groundwater. Each water sample was tested physically, chemically, and bacteriologically. Additionally, the five day biochemical oxygen demand test and hydrogen sulphide were detected. The period of the actual sampling and testing extended from mid-1990 to the beginning of 1992. The results obtained have been compared to the results of an earlier study conducted between 1978 and 1979. The investigation has also involved a statistical analysis of the variations in the sub-surface water table level in each hydrogeologic formation. The piezometric levels have been collected from monitoring boreholes/ standpipes. The levels obtained extended from the beginning of 1980 when the earliest recording started up to the end of 1991. Bahrain abstracts its fresh water from five aquifers which in descending order are the Sanad, the Alat, the Khobar, the Rus, and the Umm-Er-Radhuma Aquifers. The quality of the groundwater appears to be deteriorating. The excessive groundwater abstraction has caused the encroachment of the sea into all the sub-surface waters. As the waters become saline, they are expected to become unsuitable for human consumption and for irrigation. The deeper aquifers are believed to consist of high values of the hydrogen sulphide because the deeper geological formations contain oil rich in sulphur. land spring water is expected not to be safe bacteriologically because it is exposed to the atmosphere unlike the other boreholes in the various aquifers.The water table levels have been changing in each aquifer. The groundwater levels in the Sanad Aquifer, which is the shallowest geological formation, are expected to rise in the future in areas where the natural drainage is obstructed. This is related to the sea coast reclamation area. The rise is expected to reduce inland depending on the application of surface irrigation as well as the possible leakages from the services systems. About two kilometres south from the original shore, around Buddayya Road, the Sanad Aquifer's water table has been shown to be falling. This fall is expected to be due to overpumping from the groundwater system. Apart from the Sanad Aquifer, the piezometric levels of the underlying aquifers are expected to fall with time. Once again the fall is due to excessive groundwater abstraction. The study concludes by re-presenting the causes for the water table rise in the near-surface Sanad Aquifer and discusses the possible geotechnical consequences. It further produces some possible solutions to control the rise of the water table level.

No description available.

No description available.