Drivers on the Sabino Canyon Road bridge over Tanque Verde Creek sometimes do a double take when they spot an antenna perched above the bridge.
What could it be?
Some kind of high-tech traffic sensor that might lead to a speeding ticket? An intergalactic listening device waiting for a call from ET?
A TV receiver put up by some homeless guy living under the bridge?
OK, let's get serious. It's an antenna used to transmit data on rainfall and stream-flow levels to flood-control and weather experts.
Information from the site - and more than 90 others around Southern Arizona - helps authorities provide early warnings about possible flooding.
Data from a rain gauge and a stream-flow gauge go to a transmitter, and the radio antenna sends the information to offices of the Pima County Flood Control District and the National Weather Service, said David Janders, principal hydrologist with the district.
"We're really proud of our system," Janders said. "It's very crucial during limited times of the year" - like during the monsoon.
Similar transmitting equipment can be seen at other stream-side sites around Tucson.
Janders said the site on Sabino Canyon Road is equipped with a solar panel - as are most of the other monitoring sites.
"Ninety-three of our 95 sites are solar-powered," Janders said. "It's solar power to back up batteries (used in the monitoring system) so battery life will be extended."
Contact reporter Doug Kreutz at firstname.lastname@example.org or at 573-4192.