As the number of rainbarrels approaches infinity, the amount of water in the rivers and creeks approaches 0. Why do you hate rivers and creeks, Hungary?
Oh good grief.
Please tell me you are joking, as I think you are.
Austin and Chicago are world's apart in terms of water. Austin's is disappearing. Chicago's needs protecting.
Chicao's sewer system is antiquated and prone to failure. Storms creating excess runoff flood the sewer system, mixing raw sewage and storm water and ejecting it into Lake Michigan like a giant arse hole. The system does not have the capacity to handle it, and the fact that Chicago's sewage treatment system only filters sewage but does not disinfect it only compounds the problem.
Chicago's massive Deep Tunnel
project aims to alleviate this by diverting storm runoff into a giant resevoir carved out of Mississippian limestone to the south of the city. I am sure it's a fine idea, but it's big, expensive, and won't be ready until 2029. Here is a funny anecdote from the link:
On October 3, 1986, a heavy thunderstorm drenched the southern portion of the Deep Tunnel area with several inches of rain in a short period of time. While the Deep Tunnel system performed satisfactorily by absorbing excess water, water within the system itself rushed past the north side of Chicago and near the Bahá'í Temple in Wilmette. Geysers of over 65 feet (20 m) were reported in both locations for up to an hour as the water was redistributed more evenly through the system. A 30 ft (9 m) geyser erupted downtown at the corner of Jefferson and Monroe. A system of watertight bulkheads has since been installed to prevent the event from occurring again.
So the rain barrels collect and store runoff. Using it to water plants puts it right back into Lake Michigan after filtering through layers of sand just below the topsoil. One could not devise a more natural system.
Has Austin resorted to filtering its [expletive] yet?