Between Dec 19, 2024 and Jan 2, 2025, datasets can be submitted to DRUM but will not be processed until after the break. Staff will not be available to answer email during this period, and will not be able to provide DOIs until after Jan 2. If you are in need of a DOI during this period, consider Dryad or OpenICPSR. Submission responses to the UDC may also be delayed during this time.

Browsing by Author "Mackenthun, A. A."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Experimental Analysis of Sedimentary Oxygen Demand in Lakes; Dependence on Near-Bottom Flow Velocities and Implications for Aerator Design
    (St. Anthony Falls Hydraulic Laboratory, 1993-06) Mackenthun, A. A.; Stefan, H. G.
    Aeration technology is applied in hundreds of Minnesota lakes and reservoirs for at least three purposes: (a) to prevent winterkill of fish in shallow lakes under ice cover, (b) to reduce nutrient release rates from the sediments and (c) in aquaculture to provide aerated water to high-density fish populations. A major uncertainty in the design, selection and application of aeration systems is the often observed increase in oxygen demand after aeration systems are installed and operated. As a result, the improvement in dissolved oxygen is often less than anticipated, even zero. In this study we have investigated this problem through a series of carefully designed experiments. We have shown that sedimentary oxygen demand (SOD), frequently the major oxygen consumer in lakes, increases proportionally to the velocity with which the water above the sediments moves. Aeration devices often and intentionally increase water velocity above the sediments and thereby increase oxygen consumption in the lake. The results given in this report allow a more realistic estimation of oxygen demand in lakes for aerator selection. Recommendations for aerator placement are also given.
  • Thumbnail Image
    Item
    Experimental Study of Sedimentary Oxygen Demand in Lakes: Dependance on Near-Bottom Flow Velocities And Sediment Properties
    (St. Anthony Falls Hydraulic Laboratory, 1994-12) Mackenthun, A. A.; Stefan, H. G.
    Sedimentary oxygen demand, SOD, is the uptake of dissolved oxygen, DO, by chemical and biological processes in the uppermost portion of lake sediments. The oxygen is removed from the water column by chemical oxidation processes and by respiration of the microbial population in the sediments. Low DO kills fish in lakes and ponds, especially under ice cover, and increases nutrient release rates from the sediments. To develop DO models and to effectively counteract oxygen depletion an improved understanding of SOD is required. In this study we have investigated SOD through a series of laboratory experiments. We have shown that SOD, frequently the major oxygen consumer in lakes, increases proportionally to the velocity with which the water above the sediments moves. This velocity dependent relationship has, however, an upper bound which depends on the sediment material. The results given in this report allow a more realistic estimation of oxygen demand in lake oxygen models (budgets).