340
y = 0.0017x - 3.2003
R 2 = 0.9581
y = 0.0015x - 2.8418
R 2 = 0.9442
0.06
0.07
0.08
0.09
0.10
0.11
0.12
0.13
0.14
0.06
0.07
0.08
0.09
0.10
0.11
0.12
0.13
0.14
1990
1995
2000
2005
2010
2015
Bay Range/Ocean Range (a
B /a
O )
Mean Spring Tidal Range
(MHWS-MLWS m)
Year
Spring Tidal Range
Bay Range/Ocean Range
Fig. 10.19 Change history of the mean spring tidal range in Lake Macquarie and its ratio to the
ocean range. The trends are strong (R
2 > 0.9) showing no signs of abating. With the bay area some
110 km
2 , the increase in the spring tidal prism of 1.7 mm/a equilibrates to an annual increase in the
spring tidal prism of 190,000 m
3
y = -0.5393x + 1178.7
R 2 = 0.6831
90
95
100
105
110
1990
1995
2000
2005
2010
2015
Phase Lag (degrees)
Year
Fig. 10.20 Change history of the phase lag (bay phase minus the ocean phase) of the major spring
tidal constituent (M2) in Lake Macquarie. There is a clear reducing trend (R
2 = 0.7) indicating high
tide progressively arriving sooner in the bay
A.F. Nielsen and A.D. Gordon