TIDAL STREAMS 1 Owing to Diurnal inequality only the Mean Spring rate is shown. 2 The factor to be applied to the rate depends not on the range of the tide, but:- (a) For East-going streams upon the height of the nearest HW at Darwin above Mean Level divided by the semi-spring range, or:- Height of HW - 4.1 / 2.75 (b) For West-going streams upon the height of the nearest LW at Darwin below Mean Level divided by the semi-spring range, or:- 4.1 - Height of LW / 2.75