Figure 4: Combined plots of the six identified flow metrics assessed for
the Barossa Valley Gorge (Yaldara gauging station) in the Barossa PWRA
showing the environmental water requirement bounds (blue dashed lines)
identified as the upper and lower limits of the three year moving
average between 1997 and 2016 (orange dashed line). Grey points are
metric results for the baseline period. The moving average post 2016
(black dashed line) showing current variability in the flow regime. For
years where the moving average is outside the expected bounds, the data
point is red, if it is inside the bounds, the data point is green,
regardless of the actual position of the data point relative to the
bounds.
Across all 17 zones assessed, there were two instances where the lower
bound was zero (Low flow days over the low flow season for Lower and Mid
Flaxman Valley). The metrics for these zones was checked against the no
dams modelled data to ensure that the thresholds developed were suitable
and, in both instances, the thresholds were deemed appropriate. The
lower bound of zero suggests that the level and layout of dam
development in these zones is having such an effect that there are
periods of three or more years where there are no low flows over the low
flow season. Similarly, there were two zones, Duck Ponds Creek and Upper
Flaxman Valley, where the upper limit of the delay of break of season
was the maximum 150 days, i.e. the season did not break. These bounds
presents a problem when considering ongoing sustainability of the
riverine ecosystems of the zone and will need to factored into
assessment of environmental water requirement thresholds for water
planning.