Original paper
The effects of inflow and outflow on the seasonal behaviour of a stratified reservoir in temperate Australia - a 20 year analysis
Ferris, John M.; Tyler, Peter Alfred
Archiv für Hydrobiologie Volume 126 Number 2 (1992), p. 129 - 162
53 references
published: Nov 26, 1992
DOI: 10.1127/archiv-hydrobiol/126/1992/129
ArtNo. ESP141012602000, Price: 29.00 €
Abstract
Twenty years of thermal and oxygen data for the deepest part of a temperate impoundment are described in relation to the effects of seasonally and interannually unpredictable inflows. Lake Burragorang has a warm monomictic thermal cycle with a short (1-2 month) holomictic period which is modified in about 50 % of years by cold, stabilizing inflows that prevent the development of a physically and chemically homogeneous water column. Although similar behaviour has been considered to be a form of temporary meromixis, we argue that this is inappropriate when the advective stabilization involves upward displacement of the existing hypolimnion and the isolation of the most recently influent water which is initially well oxygenated. During thermal stratification, the hypolimnetic oxygen concentration declines at an average rate of approximately 0.58 mg l-1 (5.1 % saturation) month-1 to a minimum of from 0 to 3.8 mg l-1 (0-35 % saturation). Adjusted for temperature, this rate falls below the median rate reported for 21 European and North American lakes. In the period 1961 to 1980, hypolimnetic anoxia was recorded only once, following floods which brought very turbid water into the lake. The hypolimnetic oxygen minimum is frequently observed to form at some distance above the lake bottom and this is tentatively ascribed to the effects of the withdrawal current associated with the fixed-level hydroelectric power offtake. The descriptive account given here clearly indicates the contribution of inflows and outflows to the year variation of thermal and oxygen stratification in Lake Burragorang and underlines the importance of long term data collection as a means of understanding the extent of that variation.
Keywords
monomictic • stratification • hydroelectric power • hypolimnetic • Lake Burragorang • Australia