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Over the course of the study the average monthly surface water temperatures for July 2000, 2001,
2002, 2003, and 2004 were 13.32 ± 0.59, 13.85 ± 1.83, 11.11 ± 0.49, 14.27 ± 0.68ºC respectively. In
comparison the average monthly morning surface water temperatures for August 2000, 2001, 2002,
2003, and 2004 were 14.45 ± 0.07, 13.31 ± 13.12 ± 0.60, 14.50 ± 1.27ºC respectively (Table 3.3.5).
Average ring tank morning surface water temperatures were above 20ºC for 6 months in 2001 and
2002 and 7 months in 2003.
Variations in temperature readings between bottom and surface waters were similar although less
severe than those for oxygen. The greatest differences between ring tank surface and floor water
temperatures were observed in the afternoon. The differences between surface and ring tank floor
water temperatures were up to 3.1ºC for morning readings and 7.5ºC for afternoon readings. This large
difference between surface and floor temperatures in the afternoon is a consequence of the heating of
the upper surface waters in the summer as opposed to any change in floor water temperatures.
The highest afternoon water temperature of 33.1ºC was recorded on a single day in January 2004. The
highest floor water temperature was 29.7ºC in February of the same year. The highest monthly
averages for surface and floor water temperatures of 29.30 ± 1.66ºC and 27.19 ± 1.45ºC were also
recorded in February 2004.
Table 3.3.5 Average monthly afternoon ring tank surface (SF) and floor (FL) water temperatures
from November 2000 to March 2004 (mean ± standard deviation)
Month
2000 2001 2002 2003 2004
SF FL SF FL SF FL SF FL SF FL
January
27.82 25.91 26.21 24.83 28.10 25.16 28.34 26.83
± 1.47 ± 1.11 ± 1.16 ± 0.56 ± 1.11 ± 0.82 ± 1.37 ± 0.56
February
28.18 24.33 26.34 24.28 26.34 24.75 29.30 27.19
± 2.18 ± 0.52 ± 1.47 ± 0.35 ± 1.49 ± 1.01 ± 1.66 ± 1.45
March
25.39 23.92 24.38 23.16 25.38 23.89 25.97 25.33
± 1.44 ± 0.39 ± 0.96 ± 0.43 ± 0.91 ± 0.62 ± 1.72 ± 1.74
April
22.07 20.87 21.44 20.64 23.00 22.30
± 0.89 ± 0.83 ± 0.99 ± 0.51 ± 1.87 ± 1.70
May
18.29 17.63 17.32 16.94 18.76 18.02
± 2.22 ± 1.94 ± 1.92 ± 1.71 ± 1.42 ± 1.20
June
15.85 14.78 14.53 14.33 16.09 15.48
± 1.32 ± 0.71 ± 0.50 ± 0.48 ± 1.32 ± 1.08
July
14.25 13.52 11.88 11.26 15.02 14.35
± 1.32 ± 1.19 ± 0.78 ± 0.50 ± 0.89 ± 0.65
August
14.19 13.47 13.98 12.79 15.36 14.57
± 0.77 ± 0.29 ± 0.78 ± 0.56 ± 1.36 ± 1.32
September
17.84 16.09 17.83 16.49 18.62 17.73
± 2.36 ± 1.72 ± 1.19 ± 0.94 ± 1.99 ± 1.68
October
20.13 18.62 21.92 19.07 21.86 20.17
± 1.20 ± 0.64 ± 1.18 ± 0.97 ± 1.35 ± 1.08
November
24.16 22.27 22.09 20.79 25.26 20.86 24.63 22.30
± 1.89 ± 0.65 ± 1.04 ± 0.71 ± 1.27 ± 0.90 ± 1.51 ± 1.56
December
26.47 25.16 25.31 24.61 26.57 23.26 27.63 25.77
± 0.86 ± 0.75 ± 0.58 ± 0.33 ± 1.36 ± 0.66 ± 1.97 ± 1.30
3.3.2.3 Turbidity
Ring tank turbidity was clearly influenced by riverine pumping events (Fig 3.3.1). Prior to riverine
water harvesting activities in February 2001 the secchi depth of the ring tank was >2.5 m. These high
secchi values were as a result of filling the ring tank with water from the adjacent bore. However, as
soon as riverine pumping of flood waters commenced secchi values dropped rapidly. The day after
pumping activity ceased the secchi depth had reached 0.2 m. This decrease in secchi depth was clearly
observed to be associated with an increase in fine suspended clays rather than any increase in
phytoplankton abundance.
The lowest secchi readings of 0.1m were observed following a series of pumping events in November
and December 2001. The secchi value prior to commencement of pumping activity was 0.45 m. By the
end of November secchi values had fallen to 0.25 m. In December, secchi values averaged just 0.11 ±
13