Most people, with few exceptions, will start feeling the effects if they do without water for more than 36 hours.
Dehydration occurs much quicker than starvation.
Our bodies can tolerate the loss of food much better. With an ample water supply, starvation is delayed many days, even weeks. A major water distribution line breaks on Balboa Blvd. The city water supply is vulnerable to the effects of a large earthquake. Contaminants can get into the drinking water supply through ruptures in the pipes, the mixing up of supply sediments, the adulteration of filtering systems, etc.