Since each water bottle has a capacity of 12 liters, when filled up to 3/4 of capacity, each carries 3/4*12 = <<3/4*12=9>>9 liters of water.
If there are 50 bottles of water in each box, the number of liters the water bottles in a box are carrying is 50*9 = <<50*9=450>>450 liters.
In 10 boxes containing bottled water, the total number of liters in the water bottles is 450*10 =<<450*10=4500>>4500 liters.
#### 4500