All ALERT gaging stations communicate data using 300-baud FM radio transmissions which are rebroadcast by one or more radio repeaters. Radio interference is one common source of bad data. ALERT rain measurements are affected by wind, hail, snow, birds, insects, and lawn irrigation systems. Human tampering is a problem at certain sites. Routine maintenance activities involve manual testing of rain gages, water level sensors and other measuring devices. Electronic switches on tipping-buckets occasionally malfunction causing falsely high rainfall reports. Lightning, which occurs frequently in this region, can cause false reports that may not be apparent.

Even if all ALERT gaging stations could work perfectly, base stations are another possible error source. Currently there are 15 known ALERT base stations operating in the Denver/Boulder area which collect data independently. Consequently, some data inconsistencies between the base stations should be expected. Each base station computer uses its internal clock to attach date/time values (using GMT or Coordinated Universal Time) to data reports received from the gages. This record is then stored in a database file and the computer displays information using the current local time setting (i.e. MDT or MST). Computer clocks very in accuracy and must be reset occasionally. Internal clock batteries eventually die and must be replaced. When sensors in the field are electronically adjusted or replaced, the ALERT database must also be re-calibrated. An improperly maintained database is sometimes difficult to detect with misinterpretated data being the likely outcome. Field maintenance reports, calibration notes, rating tables and alarm settings are available for inspection at the District.

Due to the large number of ALERT stations reporting data, it is not practicable to manually correct all erroneous reports received by the base stations. Attempting to do so would require considerable effort and present yet another possible source for error. The District maintains both electronic and hard copy records of data collected by the "District ALERT Base Station" located at the District's office. Therefore, the ALERT data obtained from this base station is presumed to be the most accurate. Individuals requesting information from the District are provided with data from this base station unless a known problem requires using an alternate site. The evaluation, interpretation and verification of ALERT data from this system is the responsibility of the user.