Contribution of hypolimnetic water on metalimnetic dissolved oxygen minima in a reservoir

Abstract

A minimum in the dissolved oxygen distribution of numerous lakes and reservoirs has been observed to develop in the metalimnion during the stratified period. This minimum is usually explained by the accumulation of organic matter from the overlying layer of water. The introduction of organic matter from the interflow of storm water is also a likely contributor to the accelerated oxygen depletion within the metalimnion. Data are presented that demonstrate that even during low flow periods, water containing reduced species in the deeper upstream section of DeGray Reservoir, Arkansas, is being incorporated into a density current and transported advectively through the metalimnetic region. This mechanism may contribute significantly to the development of metalimnetic dissolved oxygen minima in reservoirs with similar stratification and flow characteristics to DeGray Reservoir.