Reservoirs In Australia Research Articles

Lake Number, a Quantitative Indicator of Mixing Used to Estimate Changes in Dissolved Oxygen

AbstractLake Number, LN, values are shown to be quantitative indicators of deep mixing in lakes and reservoirs that can be used to estimate changes in deep water dissolved oxygen (DO) concentrations. LN is a dimensionless parameter defined as the ratio of the moments about the center of volume of the water body, of the stabilizing force of gravity associated with density stratification to the destabilizing forces supplied by wind, cooling, inflow, outflow, and other artificial mixing devices. To demonstrate the universality of this parameter, LN values are used to describe the extent of deep mixing and are compared with changes in DO concentrations in three reservoirs in Australia and four lakes in the U.S.A., which vary in productivity and mixing regimes. A simple model is developed which relates changes in LN values, i.e., the extent of mixing, to changes in near bottom DO concentrations. After calibrating the model for a specific system, it is possible to use real‐time LN values, calculated using water temperature profiles and surface wind velocities, to estimate changes in DO concentrations (assuming unchanged trophic conditions).

Cholera in the Americas: Foodborne Aspects

Over 100 serotypes of Vibrio cholerae exist, but generally the toxigenic strains of the serogroup O1 cause cholera and possess documented epidemic potential. The main symptom of cholera is a profuse diarrhea resulting in dehydration, that if untreated, leads to death. Seven pandemics of this contagious disease have been recorded during the last 200 years. A sick person secrets in his stool billions of organisms daily, and water and food contaminated with such a stool are the primary sources of infection during the epidemics. With the increase of the international food trade, food is often shipped from countries with endemic or epidemic cholera. With one exception, no documented cases of cholera have been reported, as a result of the internationally regulated food trade. However, during the present Latin American epidemic, inadequately cooked seafood has been implicated as a source of cholera. As a result of the epidemic, over 100 cases of cholera have occurred in the United States related to seafood consumed during a visit to Latin America or after its noncommercial transport into the country. Furthermore, V. cholerae persists as a free-living organism in environmental reservoirs in Australia and the U.S. Gulf Coast; there have been 65 domestically acquired cases of cholera in the United States since 1973. Molecular typing methods have enabled us to identify and characterize endemic and epidemic strains, and to document transmission of cholera when food was implicated epidemiologically as a vehicle of transmission.

Sensitivity of Reservoir Sizing to Evaporation Estimates

Net reservoir evaporation is defined as the open water evaporation less the original evapotranspiration from the reservoir site. These rates are estimated on an average monthly basis by the method of Morton using sparse climtological data that include average annual precipitation, air temperature, dewpoint temperature, and sunshine ratio. Sunshine ratio data are substituted with the more generally available cloud cover data with little loss in accuracy. Generalized reservoir surface area-volume relationships are derived by regression analysis separately for large and small reservoirs in Australia. They represent the surface area-volume characteristics of a reservoir confined in a hypothetical valley whose shape is an averaging of the shapes of a large number of actual sites. The sensitivity of estimated storage sizes to errors in the evaporation rates and the reservoir surface area-volume relationships is tested for five catchments located in the southeastern extremity of Australia. With regard to these parameters, estimated reservoir sizes are shown to be surprisingly robust.