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

Publisher Website
Google Scholar
Abstract
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 reported for other streams in agriculturally developed catchments in New Zealand and North America. Respiration rates (3.50–55.0 g m‐3 d‐1) were generally larger than values reported in the literature, and P/R ratios were mostly well below 1.0, indicative of heterotrophic respiration associated with decaying vegetation and other organic inputs and consistent with diurnal DO excursions of 40 to ≥120% saturation being commonly observed. Maximum daily temperatures up to 25.7°C (median 20.5°C) were weakly negatively correlated with DO minima. Five groupings of streams were identified from DOFLO parameter values, with K 2(20) being most critical in regulating average DO deficits.

This publication has 22 references indexed in Scilit: