Geoscience Reference
In-Depth Information
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