My wife and I have a small flower garden. Living in the country, we have a well....a slow well, I might add, unlike our city dwelling friends that have an unlimited supply of water. Once a week or so I go down to the creek and fill several fifty-gallon barrels with water for our watering needs. This water may sit in the barrel for several weeks, depending on the amount of rainfall we receive. Is there any problem using this "stored" water?
As long as there are no regulations against collecting water from your creek (some states are very strict about who owns the water in creeks, rivers and even the water that runs off your roof) and the water does not contain toxins, pesticides or other materials that could be harmful to plants, there is no problem using water that sat in the barrels. You may want to use some of your barrels as rain barrels. Cover with screens to keep out debris but let the rainwater in. Toss some compressed or flakes of Bacillus thuringiensis israelensis (Bti) sold as Mosquito Dunks into the water-filled barrels to control mosquitoes. Then you don’t have to worry about toxins in the water nor spend as much time and energy hauling water from the creek.