ALERT stands for Automated Local Evaluation in Real Time, which is a method of using remote sensors in the field to transmit environmental data to a central computer in real time.
This standard was developed in the 1970's by the National Weather Service and has been used by the National Weather Service, U.S. Geological Survey, Army Corps of Engineers, Bureau of Reclamation, numerous state and local agencies, and international organizations.
There are a vast number of types and manufacturers of ALERT hardware and software, but they are all designed to meet a common set of communications criteria. Because of this, most equipment and programs are interchangeable, which has allowed for competition to improve performance and reduce cost. ALERT systems have become a standard in real time environmental data collection because of their accuracy, reliability, and low cost.
The ALERT system uses "automatic" telemetry gauges for data collection. This means that the gauges transmit their information to the base computer via VHF radio. The computer can then quickly compile the information and display it on computer screens. The rain and stream gauges are powered by 12-volt batteries, which are recharged using small solar panels attached to the top or sides of the gauges.