Table 4, Qualitative comparison of the environmental performance of a linked-basins TPP at Fundys Shepody Bay (HB) and Cumberland Basin(LB), vis–vis the chosen standard of comparison, a single-basin, DE-TPP, Type Z, at Fundys Cumberland Basin. The tabulation shows which of the two types scores highest for optimum environmental performance.

NOTE:Re D, Sea-mammal survival: TPPs should be designed and operated to keep sea mammals away from the hydraulic turbines. This applies equally to both linked-Bs and Type Z and therefore does not affect a comparison between them.
DE = double-effect; SE = single effect; HB = high-basin; LB = low-basin Linked-Bs = linked-basins

Environmental effects A B C E F
Type of TPP Linked-basins, SE, Fundy (HB and LB) Single Basin, DE at Fundy (LB)
TPP parameters
Mean, natural tidal range 10.m 10m
Mean tidal range within high basin as % of natural tide 34 % 68 % Z Z Z
Mean tidal range within low basin as % of natural tide 36% 68% Z Z Z
Mean water level within high basin, compared to natural conditions +2.9m -0.12m Z Z
Mean water level within low basin. compared to natural conditions -2.6 m -0.12m Z Linked-Bs
Number of passes through turbines, for a fish going in-and-out of TPP 1 2 Linked-Bs
Plant operation at or close to the rhythm of the natural tide no yes Z
Maximum head across turbines 6.96m 4.62m Z
Maximum water velocities through turbines 15.6m/sec 11.9m/sec Z
Stagnant flow within high basin % of the time 42% 18% Z
Stagnant flow within low basin.% of the time 42% 18% Z
Simplicity of flow patterns See Fig. 5 Z
Total scores for Iinked-Bs, SE-TPP 0 0 1 1 0
Total scores for Type Z (DE) plant 5 4 2 1 3