Environmental Monitoring of Algal Blooms in a River System

CAS DataLoggers recently provided the data-logging solution for an environmental organization monitoring an outbreak of algal blooms in a major river. The slime-colored blooms had formed as a rapid increase in the population of aquatic photosynthetic microorganisms (such as phytoplankton or cyanobacteria) to the extent that the water became noticeably discolored. First a research team was formed to ascertain all the factors contributing to the outbreak. Researchers hoped that there was a way of allowing the river’s natural forces to inhibit its algae growth, given that the river was also dammed at frequent intervals by a system of locks and weirs. To this end, they required detailed knowledge of weather conditions on the river’s surface and a highly-accurate temperature stratification profile within the river itself. The team began looking for a stand-alone datalogger with battery backup which could connect to a wide range of environmental sensors for unattended logging. High durability and easy USB data retrieval were also musts.

Project researchers installed a dataTaker DT82I Intelligent Data Logger inside a portable Pelican case also provided by CAS DataLoggers, which was then placed in the river on a floating pontoon containing a weather station. The datalogger was then connected to a variety of sensors monitoring temperature, relative humidity, solar radiation, and wind speed/direction, along with a vertical column of 20 thermistors for precise water temperature readings. The dataTaker was also connected to a GSM modem which enabled researchers to access the data from their city office, and was easily programmed to accept the analog signals from the sensors at predetermined intervals, convert them to digital form, and store them for later downloading to a notebook PC.

The stand-alone DT82I datalogger provided the project with an extensive array of features including USB memory stick support, 18-bit resolution, extensive communications capabilities and a built-in display. The dataTaker’s Dual Channel concept allowed up to 4 isolated or 6 common referenced analog inputs to be used in many combinations, and the universal inputs enabled users to take measurements from almost any sensor type including thermocouples, RTDs, and thermistors, and many others. The DT82I formed a totally self-contained solution featuring support for FTP and Web interfaces, and regulated outputs to power sensors. Researchers left the dataTaker to log unattended using its internal battery for extensive operation, only visiting the station on a weekly basis to retrieve the data via USB stick; if necessary, the data could have been stored for much longer periods.

Equipped with superior data storage and communications features, the dataTaker was able to store up to 10 million expandable data points so that as much or as little data could be recorded as needed. After filling allocated memory, users could overwrite or stop logging, archive data on alarm event, copy to USB memory, or transfer via FTP to provide data via the Internet or mobile phone network without any need for polling or specific host software. The built-in dEX web interface allowed users to configure the DT82I, access logged data, and view measurements as mimics or in a list using a web browser.

The river monitoring project got off to a good start following installation of the dataTaker DT82I Intelligent Data Logger. The logger’s universal inputs allowed connection with all the weather station’s environmental sensors to accurately measure the river’s surface temperature and other key conditions, while connection with the GSM modem and USB stick support made data collection hassle-free. After a month of collecting and analyzing the pontoon’s readings, it was found that the algal blooms had resulted from an excess of nutrients spread through fertilizer entering by water runoff. Identifying the cause helped team members to better inform local residents about algae prevention and water safety techniques.

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