Continuous data helps Kentucky watershed

By on December 23, 2011

A continuous stream of data from a small Kentucky watershed is helping researchers find out what’s keeping an impaired creek from meeting its potential.

The data will help identify the problems in Brushy Creek watershed that keep the creek from meeting it’s designated uses identified under the Clean Water Act. Previous work by the state found that the creek’s support for warm water aquatic habitat is impaired.

“We’re trying to find the cause of the impairment,” said Mike Croasdaile, professor of civil and environmental engineering with the University of Louisvilleā€™s Stream Institute.

Croasdaile and Stream Institute post-doc Raja Nagisetty are coordinating the monitoring project for the Pulaski County Conservation district, funded through a 319(h) grant from the Kentucky Division of Water.

The monitoring system includes five YSI 600OMS sondes measuring temperature, conductivity, and turbidity every 15 minutes. An additional YSI 6920 V2-2 measures temperature, conductivity, turbidity, pH, and dissolved oxygen every 15 minutes and broadcasts the data online every hour via a NexSens 3100-iSIC cellular data logger.

The continuous measurements have shown very low dissolved oxygen levels that may have gone unnoticed if the researchers were relying on spot samples alone, he said.

During monthly spot sampling the dissolved oxygen was always above surface water standards, but the sonde data showed prolonged periods during late summer where dissolved oxygen was very low.

This summer, oxygen levels were dropping below 2 milligrams per liter, which is too low for organisms like big fish to handle, he said.

The researchers are taking spot samples to measure E. coli levels, which have shown to be extremely high. Though E. coli isn’t measured continuously, Croasdaile said the researchers will look for correlations between their E. coli data and sonde data to identify parameters that could help predict high pathogen levels. The method could also work for nutrients.

“We’re using the sondes to develop predictive models for some of these other parameters which you can’t measure continuously,” he said. “If you know when the stage is rising and you know what the turbidity is, then maybe you can make a decent estimate of the phosphorous concentration.”

Having their data telemetered online with a NexSens cellular data logger has helped quality control, Croasdaile said. It allows the researchers to keep an eye on things and check that everything is working. If it isn’t, they can quickly replace a sensor or troubleshoot a problem.

While scientists have been measuring conductivity and dissolved oxygen for decades, data from traditional spot sampling can only show a snapshot in time. The long time series of data made available by sondes can help scientists use these parameters as a diagnostic tool to understand the problems in a watershed, Croasdaile said.

“When you use these sondes, you get a high resolution time series and you really get a dynamic view of the ecosystem and the water quality,” he said. “The time series really helps us interpret the behavior of the system. You just don’t get that with grab samples.”

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