Dissolved oxygen dynamics in a shallow stream system

Bjoern Michaelis, University of Rhode Island

Abstract

Dissolved oxygen dynamics in a shallow stream system were analyzed under dry weather conditions on the Blackstone River in the state of Massachusetts. A dissolved oxygen modeling was conducted with the enhanced stream water quality EPA model QUAL2E by Brown and Barnwell (1987). The dissolved oxygen model was successfully calibrated and validated for dynamical simulations. The accuracy of the model results was proved by graphical and statistical comparison. ^ A procedure is provided to simulate chlorophyll a in QUAL2E with higher accuracy, based on converted photosynthetically active radiation (PAR) and extinction coefficients of PAR in the water column. The significance of PAR is shown by graphical and statistical comparisons. ^ The significance of analyzing correct computation of the long-term BOD rate, k1, is shown. ^ A procedure of measuring the “true” SOD is presented. It was found that the respiration by periphyton might have a significant impact on the SOD value. ^ In the Blackstone River, productivity in the recent dry weather surveys (2000–2003) was mainly caused by macrophytes and phytoplankton. In contrast, the Blackstone River in 1991 did not indicate the frequency of any macrophytes along the stream but high densities of phytoplankton between BAC15 and BAC24. Daily average gross productivity rates were computed with two methods. The results were valuated with daily average gross productivity values obtained from the calibrated and validated dissolved oxygen model in QUAL2E. ^ Macrophytes played a decisive role in the removal of dissolved phosphorus from the water column. ^ A sink and source inventory of dissolved oxygen was conducted for the recent dry weather surveys and for the dry weather surveys of 1991. For the recent dry weather surveys, the greatest sink of dissolved oxygen was found to be caused by nitrification followed by SOD. For the dry weather surveys of 1991, the sink nitrification played an insignificant role. The greatest sink was caused here by SOD along the entire river. ^ UBWPAD was the greatest source for all nutrients and therefore ranked first over all sources. Sources such as tributaries or non-point sources such as groundwater only played a minor role. ^

Subject Area

Engineering, Environmental

Recommended Citation

Bjoern Michaelis, "Dissolved oxygen dynamics in a shallow stream system" (2005). Dissertations and Master's Theses (Campus Access). Paper AAI3186915.
http://digitalcommons.uri.edu/dissertations/AAI3186915

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