Succinctly put, bees need bee food and water to survive. Bees rarely store water, but bring it in as needed, so it is vital to provide fresh water to them continuously. Below you'll learn what bees use water for, why honey bees need water, and how you can provide water easily.
This is the first time I have planted anything from seeds, and with the terrible soil in my yard I didn't expect anything to really take. Boy, oh boy how they took! The area I planted in is covered in flowers and they are lasting such a long time... I have had the same blooms for the last couple of months. I am so excited to buy more Seedles and cover as much of my barren land in beautiful flowers as I can. - Karly Perez, Michigan
A red tailed hawk swooped down into my father-in-law's backyard and quickly landed. The two rock pigeons quickly dove for cover into nearby green hedges, and the tiny sparrow took flight as well. It wasn't meal time, it was water time. The bird bath although degraded and leaky after 20+ years outdoors still held some water in the dead of summer. It was a place of congregation in their dry, drought-laden California suburb of San Francisco.
What was most common there though was honey bees, 10-15 of them lined up regularly sipping up water like thirsty dogs. The neighbors hives enjoyed a regular supply of water without the risk of drowning considering there were plenty of cement edges for the bees to hang out on.
I've seen small native bees, honey bees, bumble bees, carpenter bees, and a black/blue bee once that I'm still not quite sure what it was.
Bees Use Water For
Cooling - In the heat of summer it is used for evaporative cooling. Similar to human-designed air conditions, the bees spread a thin film of water atop sealed brood(baby bee cells) or on the rims of cells containing larvae and eggs. The workers inside the hive then fan vigorously, setting up air flow which evaporated the water and cools the interior of the hive.
Humidity - Worker bees use water to control the humidity of the colony, not just the temperature.
Utilize Stored Food - Bees need water to dilute stored honey that has crystallized (become too high in glucose) or in the case where beekeeper feeds them dried sugar crystals, they need water to dissolve the sugar. Without water, they can't access these food sources.
Larvae Food - Another type of bee in the hive is the nurse bee, who feeds the developing larvae. They consume large amounts of pollen, nectar, and water so that their hypopharyngeal glands can produce the jelly that is used to feed the larvae. A larvae diet can consist of water up to 80 percent the first day of larval growth and about 55 percent on the sixth day. 
Digestion - They need it in the digestion and metabolization of their food, as do most organisms.
"Foragers will mark unscented sources of water with their Nasonov pheromone so others can locate the source too," Flottum writes.
Why They Need Clean Water
Chlorine - In a suburban environment, we recommend giving your bees fresh water to keep them out of your neighbor's swimming pool. Not only can the water contain chlorine and other contaminants, it may also bother your neighbor.
Larvae Development - Hypopharyngeal glands are less developed in workers starved, poisoned with pesticides and other anaesthetics.  The nurse bees and other bees use these glands to feed the larvae. During 24 hours the queen is able to lay more than 2000 eggs (larvae). That's a lot of mouths to feed!
There are many ways you can help bees get some water during the summer heat, spring or fall. It's not as important how you do it, it's more important it gets done.
Easy Ways To Give Honey Bees Water
Key Tips For Watering Feature For Bees
Shallow & Wide - Bees don't need a deep bucket, just a small amount where they can't drown.
Corks, Rocks, or twigs - Always place floating wine corks, rocks, or glass pebbles so the bees have a place to get near but not drown in the water
Fresh Water - It is important the water is refreshed every day or every other day, so under a leaky outdoor faucet is a good spot to place a watering feature.
Best Honey Bee Watering Ideas
Frisbee With Rocks - Put a frisbee full of clean rocks (find them in your yard) underneath a faucet outside, turn the faucet on so it drips once per minute. Over the day it will fill up and provide fresh water for the bees.
Glass Pebbles - Most art stores, dollar stores or Target like stores have those bags of glass pebbles you can buy. Buy 1-2 bags of these pebbles and put them in a large (6 or more inches) but shallow container. Fill this with fresh water daily and place it near your garden or outside in a natural area of your yard. Bonus if you put some water loving plants like horsetail, cattail, water loving ferns, etc
Birdbath - Take over the bird bath and decorate with twigs, rocks, pebbles, and wine corks. Ad some green ferns or moss to add a bit of color.