Geoscience Reference
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Figure 11.3. The late Pleistocene Willandra Lakes in semi-arid New South Wales,
Australia. (After Bowler et al., 2011 .)
In this expression, A c is the catchment area, P c is the mean annual precipitation
over the catchment, k is the run-off coefficient, A w is the surface area of the lake, P w is
mean annual precipitation over the lake and E is the mean annual surface evaporation
from the lake. It follows from this expression that if evaporation is very low and
seepage losses are minimal, a lake can sustain a high level even if precipitation is
relatively low. Oviatt ( 2000 ) offers a variant on this lake water balance equation:
=
A L (
P L
E L ) + (
) + (
G 1
G 0 )
V
R
D
(11.2)
In this expression,
V is net change in volume of the lake, P L is precipitation on the
lake (expressed as depth), E L is evaporation from the lake (expressed as depth), A L
is area of lake, R is run-off from the catchment, D is surface discharge from the lake,
G I is groundwater inflows and G I is groundwater outflows.
11.3 Classification of desert lakes: amplifier and reservoir lakes
Not all desert lakes are sensitive to local climatic fluctuations. Street ( 1980 ) discussed
the relative importance of climate and more local geological and hydrologic factors
influencing lake level fluctuations and drew a useful distinction between 'reservoir'
lakes and 'amplifier' lakes, with the latter being especially sensitive to climatic change.
Reservoir lakes are akin to beads on a rosary or pearls on a necklace, and form part of
an integrated drainage network, with water flowing in from rivers upstream and out to
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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