What BLU needs are alternatives to Water Cannon, as it's a little odd they only have one single target spell. Most spells are similar with only the elemental affinity being different. So here are the 5 added elements to go with Water Cannon.

Spell: Delivers (element) damage with a potency of 120.
Cast/Recast: 2.5s
Range: 25y
Radius: 0y

Water Cannon: Water damage
Thunder Dart: Lightning damage
Blaze Blast: Fire damage
Ice Beam: Ice damage
Dust Storm: Earth damage
Gale Missile: Wind damage