How do I acess the combined variables for sprites

So if I have 10 lakes and each lake has a variable water how could I see the combined amount of how much water each lake has?

one way would be having a global variable TotalWater

trigger once (or another triggered event)

System set TotalWater = 0

-- for each lake

System TotalWater add lake.water

Hmm ok I'll try that thank you