The reasons why cats paw at the ground before drinking water are as follows:
Cats are very picky about the quality of their drinking water. So, digging before drinking could be due to the water not being changed for a long time, causing it to become contaminated. It could also be due to a strong, unpleasant odor in the surrounding environment. Cats have a highly developed sense of smell, making it easy for them to detect changes in their surroundings. It could also be that the owner hasn't disinfected or cleaned the cat's water container in a long time. 
Here are some ways to stop your cat from pawing at the ground before drinking water:
Owners should clean the container and change the water daily to avoid being disliked by their feline overlords.
