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An AIC hydrometeorological station monitors conditions in aremote, arid area of Argentina.
In a country as large as Argentina, monitoring growingconditions in different agricultural regions is a formidabletask. Significant parts of the country are dry, making wateruse and distribution critical. To help in this effort,supervisory control and data acquisition (SCADA) is being used tomonitor and control flow through two large dams that supply waterto the country’s main fruit growing regions.
This instrumentation helps balance irrigation requirementsagainst maintaining adequate water levels in the rivers used totransport most of Argentina’s products.
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Map of central Argentina shows the area of study (hachured) andlocation of the central control station(circle). Map of SouthAmerica (inset).
The hydrometeorological system was designed for the AutoridadInterjurisdiccional de las Cuencas delos Rios Limay, Negro yNeuquen (AIC). The AIC is responsible for managing the watersupply from the Neuquen, Limay, and Negro Rivers to the country’spomological regions. Electronica Naval, an Argentinean companybased in Buenos Aires and Mar de Plata, won the contract to supply80 stations to the AIC. The system monitors a 100,000km2area,the closest sites being 60 km apart and the central controlstation roughly 500 km from the distal sites.
One of the most pressing problems for the AIC is communicatingwith the remote stations. Rapid collection and exchange ofmeteorological information is hampered by mountainous terrain, lackof roads, and a poor telecommunications infrastructure. Thecommunications systems (telephones,X.25 data lines) inside thecountry are expensive and not very reliable. Telephone linesare used where functional to query the remote sites, withX.25 datalines as a back-up. The more remote sites use Inmarsat-Csatellite transceivers for communication.
Remote monitoring via Inmarsat-C uses a two-way global datasatellite net-work. The satellite communication ser-vice isprovided by Inmarsat, an international mobile satelliteorganization. There mote hydrometeorological stations arebased around a Campbell Scientific CR10datalogger,a TrimbleNavigation Galaxy Transceiver, and a special datalogger PROMdeveloped by Campbell Scientific to work with Inmarsat-C.
By January 1996,forty-two stations were installed andoperational. Fourteen stations are located on mountaintops,16are in the foothills, and 12 are on the plains. Helicopters were used to install the mountain-top stations. During the winter, almost all of the stations are inaccessible dueto rugged terrain. The second stage, consisting of 23additional stations, should be in place by late 1997.
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The Inmarsat-C satellite system provides telecommunications forremote Argentine stations.
The system has worked flawlessly since installation. Nostation has required repair, demonstrating the equipment’s abilityto function in temperatures less than -15°C and in winds up to 100km/h. The sensors used in this project are:
•Met One’s 014A/024A Wind Speed and Direction Sensors
•Vaisala’s HMP35C Temperature/ Relative Humidity Probe
•Vaisala’s CS105 Barometric Pressure Sensor
•REB’s Q-7 Net Radiometer
•Hydrological Services’CS700-L Rain Gage
•Handar’s 436B SDI-12 Incremental Shaft Encoder
•Keller PSI’s CS405-L Submersible Pressure Transducer
At each remote station, the sensors are measured by a CR10, witha unique pro-gram defined by its sensors and transmissionrequirements. The CR10s are programmed to read the sensors atvarying time intervals, and alarm callouts are customized for eachsensor. The central station polls each remote station to viewreal-time or historical sensor measurements, to change thetransmission period, or to change the alarm levels of eachsensor. Typically the date, time, battery level, and sensorreadings since the last transmission are sent in 20- to32-bytepackets. Additional output parameters such as maximaand minima can also be programmed into the CR10 from the centraloffice. When an alarm transmission occurs, the controlcentral operator can access real-time data immediately.
The CR10 controls power to the satellite transceiver with one ofits control ports. By switching power to the Inmarsat-Ctransmitter or by shortening transmission periods, battery power isconserved. A solar panel provides power to the remotestations with battery back-up for nighttime or periods ofdiminished sunlight. Continuous data records are a higherpriority than data transmission. If the system batteryvoltage falls below a preset level, the CR10 turns the transmitteroff until power recovers. This ensures power levels aremaintained for continuous sensor measurement and data storage.
The dataloggers used in the remote stations have 64 Kbyte ofdata storage, allowing data collection and data transmission to beindependent. Data can be collected hourly or as protocoldemands. Scheduled data transmission occurs every4 to 6 hours;alarm transmissions occur randomly as needed. Dataloggerclocks are updated daily through the Global Positioning Systemincorporated in the Inmarsat-C, ensuring precise timekeeping.
Electronic a Naval developed the control and communicationprograms to transfer data from the network to the controlstation. The pooled data can be printed, used to producecharts and tables, or incorporated into AIC forecast models. Futureplans include adding sensors to remote stations and controlmechanisms or by pass valves to dams.
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