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Surface Water


ALERT Technology


ALERT is an acronym for Automated Local Evaluation in Real Time. The phrase “real time” refers to the fact that data from a rain, stream, or weather gauge may be received within minutes after a measurement is automatically stored and transmitted.

Gauges have been placed at strategic locations around the State.  Typical sites for a gauge include washes, dams, low lying streets, areas where there is limited radar coverage and areas of recent fire where increased runoff and debris flows can create an increase in flood hazard.


ALERT Weather Station on Magma Dam

How does an ALERT System work?

ALERT technology relies on a radio signal sent automatically from a gauge transmitter, which is housed in an aluminum standpipe.  An enclosed tipping bucket rests atop the standpipe and measures precipitation by “tipping” back and forth with every 1 mm (0.4 inches) of rainfall.  Streamflow is measured using a transducer or other highly sensitive device located in or above the streambed.  Power is generated to the transmitter with a 12-volt battery, which is recharged daily by a solar panel mounted to the top of the antenna mast on the standpipe.

The transmitter can be programmed to send data at regularly scheduled intervals, such as every 15 minutes, or at a specified incremental change.  Most tipping buckets record every 1 mm (0.04 inches) of rainfall. Stream gauges are usually programmed to initiate a data transmission for every 0.05 foot of change in stream level, but can be programmed to transmit changes as small as 0.01 foot.

Gauge radio transmissions work by a method known as “line-of-sight”.  The radio signal may be received directly by a base station antenna, or, if the station is too far away, by a mountain top “repeater” antenna. This antenna transmits the data along to the next line-of-sight repeater antenna, if necessary.

The final destination of the data is a base station.  ADWR, ADEM, NWS, and several local entities own and operate a base station to receive transmitted data. The base station is equipped with a receiver, decoder, computer, and specialized software that convert the radio signal into a measurement.

Red Mountain

Black Hills


Red Mountain Repeater

Black Hills Precipitation Gauge

Heliograph Peak Precipitation Gauge



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