浮漂水文观测
Campbell Scientific Australia’s Chris Kellet installs theunderwater thermistorchain on Ross River Dam’s weather station.
When something occurs only once every 200years,it is worthre-cording. When that something is as unpredictable as an extremeweather event, you need to collect as much data as possible and therecord has to be accurate. Reputations of individuals and agencieshinge on it, future municipal planning depends on it.
浮漂水文观测
That’s why universities, meteorological bureaus, and otheragencies the world over turn to Campbell Scientific equipment whenonly reliable, accurate, meaningful data will do. And it isprecisely why the aftermath of1998’s Cyclone Sid near Townsville,Australia is remembered as more than just a once- in-a-lifetimestorm. On January 10th, 1998 Cyclone Sid crossed the coast50miles north of Townsville.
Sid was a slow-moving, Category 1cyclone which resulted inlittle wind dam-age. Once inland however, it formed into arain depression and saturated Townsville and surrounding areas. Inone night, more than 650 mm (25.6 inches) of rain fell on theregion. The level of Townsville’s Ross River Dam (capacity of214,000 megalitres or 56,500 million gallons) rose from 72 percentcapacity to 2.5meters (8.2 feet) over the spillway wall in littlemore than a day. It was easy to say it was an historic event, butcould it be proved?
浮漂水文观测
Ross River Dam water temperature profile over the flood eventshows temperature divergence with influx of fresh water andturbulent mixing.
Just over 12 months prior to Cyclone Sid’s arrival, the localcouncil made the decision to purchase an automatic weather stationto monitor evaporation rates and water temperature of thedam. The Townsville region has annual evaporation rates ofaround 2.5 meters (8.2 feet) per year and measurement is criticalin man-aging the city’s water supply, particularly when supplylevels are reduced. Water temperature profile measurementswere also required to assist water supply engineers in detectingtemperature inversions which can lead to algal blooms.
Campbell Scientific Australia and the New South Wales Departmentof Land and Water Conservation worked together to design, supplyand install a buoy-mounted automatic weather station capable ofmeasuring wind speed and direction, humidity, solar radiation,rainfall and air and water temperatures. The weather stationwas mounted on a 3-meter mast above a buoy with thermistors mountedon a chain trailing down to 12 meters below the surface. Avoice-synthesized modem with cellphone was installed to provideboth voice and computer access to the floating station. Twelve months worth of data was routinely collected before the‘main event’ arrived.
By 8 p.m. on the night of SaturdayJanuary10th,rain was fallingat a rate of100 mm (4 inches) per hour, gradually decreasingthrough 7 a.m. the next morning. Despite being severelybuffeted by wind and torrential rain for several hours, the CR10Xlaboriously collected what
was soon to become historic data. Two days after theflood, heavy cellphone usage and extensive cloud cover resulted inthe battery supply voltage falling below the 12 volt minimumrequired to power the cellphone and communications were lost untilsufficient sunlight returned. TheCR10X datalogger however,maintained acontinuous data record throughout, and after thecritical event.
Cyclone Sid was recorded for posterity—a 200 year averagerecurrence storm event, now an invaluable source of knowledge forpresent and future planning
浮漂水文观测
Inside the Measurements Down Under
The floating weather station on Ross River Dam is anchored tothe reservoir bed by a system of counter-weights and pulleys,creating a fixed lateral position while still allowing buoyancy.Even in heavy waves, the mast remains vertical thanks to a gimbalblock attachment to the buoy. Beneath the surface, a thermistorchain is suspended from the buoy to measure temperatures at depthsto 12meters.Above-buoyinstrumentationincludes a Campbell ScientificCR10X datalogger which records and stores raw data and isprogrammed to calculate evaporationrates as well. Data retrieval isaccomplished via cellular telephone, live in real time, through avoice synthesizer, or by downloading directly to council offices.Once the data are stored, displays of three-dimensional graphs canbe created using CSI’s RTDM software.
浮漂水文观测