Reaeration in open-channel flow

Twenty‐three lowland streams throughout the Waikato region, New Zealand, in catchments having a wide range of land uses and intensities, were monitored continuously over 3–4‐day periods for changes in dissolved oxygen (DO) and temperature. A single‐station diurnal curve model, DOFLO (Dissolved Oxygen at Low Flow), was used to produce reach‐averaged values for: K 2(20), the reaeration coefficient at 20°C; P max., the maximum daily rate of photosynthetic production of oxygen; R 20, the daily respiration rate at 20°C; and Q 10, the ratio of respiration rates 10°C apart. In addition, 24‐h average values for the ratio P/R were calculated and maximum and minimum values of DO and temperature tabulated for each site. Values of K 2(20) (0.05–40 d‐1, median 6.0 d‐1) were in broad agreement with values calculated using a modified form of the O'Connor‐Dobbins equation. Values of gross primary production in daylight (0.5–29.2 g m‐2 d‐1) calculated from P max. (1.75–86.5 g m‐3 d‐1) were similar to data reporte...

https://www.tandfonline.com/doi/pdf/10.1080/00288330.1998.9516806

Characterisation of lowland streams using a single‐station diurnal curve analysis model with continuous monitoring data for dissolved oxygen and temperature

Aquatic herbicides and the control of water weeds

The physical, biological and chemical conditions leading to a mass mortality of adult salmon (Salmo salar L.) in the lower reaches of the R. Wye are described. As a result of sunny and low flow conditions during late June 1976, water temperatures increased to a maximum of 27.60 C and accelerated the decay of substantial plant stands, the growth of which had been enhanced by the prevailing conditions: this resulted in severe deoxygenation of the water. It is concluded that the low oxygen concentration in the water at this time was the principal factor in causing mass mortalities of fish and was probably accentuated by high water temperatures.

http://www.jstor.org/stable/pdfplus/2402554.pdf

Mass Mortalities of Adult Salmon, Salmo salar, in the R. Wye, 1976

The river Kleine Elster was studied as a typical example of slowly running waters of the lowlands with dense growths of submerged macrophytes. Photosynthetic oxigenation was found to be a function of biomass and light intensity as long as the biomass did not exceed 250 g (dry mass) per square meter. Crops going beyond this limit caused a substantial decrease in oxygen supply in the early morning hours. A biomass exceeding 250 g/m2 also gave rise to critical situations in autumnal oxygen budget (dying of macrophytes), increased water level, retardation in flow and a drop in atmospheric oxigenation. Necessary management practices (cutting of weeds) were derived from the objective of stabilizing the oxygen balance.

Ron W Edwards

Papers

Plants as oxygenators in rivers