SACRAMENTO, Calif. (AP) -- A fleet of foot-long robots has floated down the Sacramento River to measure delta water flow, detect pollutants and monitor fish.

The 100 GPS-equipped devices, 40 of them fitted with propellers, were let loose from Walnut Grove on Wednesday for a two-mile journey to demonstrate the Floating Sensor Network.

The project is led by University of California environmental engineer Alexandre Bayen and graduate student Andrew Tinka.

The San Francisco Chronicle (http://bit.ly/IMIE3v ) says the sensors are designed to detect pollutants, measure changes in salinity, monitor fish life and warn of levee breaks, oil spills or other hazards.

Mini-computers in each robot are programmed with a map that allows them to avoid riverbanks and obstacles.

GPS-enabled cellphones allow the devices to transmit information to the Lawrence Berkeley National Laboratory.

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Information from: San Francisco Chronicle, http://www.sfgate.com

Copyright 2012 The AP.