Background aspects of lake restoration: water balance,heavy metal content,phosphorus homeostasis |
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| Authors: | A Lerman A B Hull |
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| Institution: | (1) Present address: Department of Geological Sciences, Northwestern University, 60201 Evanston, Illinois |
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| Abstract: | Perturbations of the lake water balance, inputs of heavy metals to lakes, and intensifying fertilization of lakes through
input and accumulation of phosphorus—these three classes of phenomena are among the more important background processes in
lake restoration. Lake restoration consists of a series of measures animed at producing a homeostatic response of a lake system
to external perturbations. The success of its implementation is affected by the morphometric and edaphic parameters of different
types of lakes. The relationship between the volume (V) and mean-depth
of fresh-water lakes indicates a trend of
. Glacial lakes occuring on or near crystalline shields have relatively shallow depths, whereas volcanic lakes, rift valley
and deep valley lakes have relatively greater depths for the same volume. For saline lakes (21 lakes, V>1 km3) that undergo cycles of expansion and shrinkage, the V to
relationship is closer to power 1. Water residence times (τ) of small and big fresh-water lakes show a trend of τ approximately
linear in
or τ∝V0.3. Volcanic lakes and Maare have longer residence times in comparison to other lakes of similar volumes. For the major inorganic
chemical species and heavy metals, the regulatory upper-limit concentrations in drinking water in the USA and EEC are from
several times to more than 100 times higher than their concentrations in a global mean river water. Only three elements (Fe,
P, and Al) occur in river water at concentrations approaching such upper-limit recommendations. Rates of accumulation of phosphorus
in lake water and sediments, computed as the difference between input and ouflow removal rates for 23 fresh-water lakes, are
generally lower for lakes of longer water residence time. The rate of accumulation is a measure of homeostatic response of
the lake system to input load: it is equivalent to the rate of all the removal processes needed to maintain phosphorus concentration
in lake water at a steady state. |
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