**Water Spout:**

150 × CurrentHP ÷ MaxHP

Therefore **when your Current HP is 3/5 or 0.6 that of your Max HP**, Water Spout is the same power as Surf because:

[n = Max HP]

150 x 0.6n ÷ n = 90

n ÷ n = 1

150 x 0.6 ÷ 1 = 90

**Brine:**

Power doubles if opponent's HP is less than 50%.

So **its' power has no relevance to when Surf's power is greater than Water Spout's** because they change depending on different variables: Water Spout = Your HP and Brine = the opponets's HP.