Abstract
To evaluate the diurnal and seasonal Dissolved Oxygen (DO) variations and their effects on water quality, a comprehensive study was conducted in a eutrophic polymictic reservoir under artificially aerated and non-aerated conditions. The effect of aeration among sampling locations and along the water column of DO and DO saturation and diurnal variation of DO, water temperature, pH and conductivity was evaluated under aerated and non-aerated conditions. Dissolved oxygen and water temperature exhibited diurnal variations under aerated and non-aerated conditions; however, no notable diurnal variation was observed in conductivity and pH. The anoxic condition was observed in near-bottom waters at night under non-aerated conditions. The diurnal DO concentration at the surface level was higher under non-aerated conditions than aerated conditions. The diurnal DO variation implies that excessive algae and weed growth cause a major impact on DO production and consumption during the day and night, respectively. The DO concentration at different sampling locations revealed that artificial aeration increased DO concentration in the deep portion of the reservoir. However, results showed that the existing aeration system was inadequate to increase the DO concentration in the entire reservoir.
Highlights
This paper evaluates diurnal, spatial and temporal variations of Dissolved Oxygen (DO) and their effect on water quality under artificially aerated and non-aerated conditions in a eutrophic polymictic reservoir
A 24-hour sampling was carried out to study the effects of algal growth due to nutrient enrichment on diurnal Dissolved Oxygen (DO) variation in the water column during summer months
The Heinrich Martin Dam Impoundment (HMDI) air compressor was on operation for 5-6 months per year in early summer prior to lake stratification and disconnected during late fall and winter months (November-April)
Summary
This paper evaluates diurnal, spatial and temporal variations of Dissolved Oxygen (DO) and their effect on water quality under artificially aerated and non-aerated conditions in a eutrophic polymictic reservoir. Eutrophic conditions are often associated with an increase in algal biomass and frequent hypoxia in aquatic ecosystems indicate eutrophic conditions (Rabalais et al, 2010; Paerl et al, 2011). The proliferation of undesirable phytoplankton in fresh and marine waters presents and ongoing problem to world’s aquatic ecosystems (Steffen et al, 2014). Nuisance algal blooms cause DO depletion and hypoxia or anoxia in the aquatic ecosystems (Stewart and Lowe, 2008; Michalak et al, 2013; Zhou et al, 2013). To maintain a healthy aquatic life, the daily minimum DO requirement claimed to be 5 mg/L in the water column (NDDoH, 2010); amount of DO needed to prevent mortality differs among species and between life stages. Hypoxia (i.e., DO
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