California’s San Joaquin River has undergone many changes over the last century. The river, which flows past a rich agricultural region on its way to San Francisco Bay, is diverted for drinking water and crop irrigation, and is dredged for ships traveling inland to the Port of Stockton. Such alterations affect the health of the river’s water, the flora and fauna along its banks, and the fish and other creatures that live within it.

The San Joaquin’s situation is not unique; all over the world, people are increasingly concerned about the health of rivers. The first step toward enacting effective remediation measures is accurately assessing the state of a river. Policy makers rely on scientists and other researchers to collect and interpret reliable data, and at least one scientist is using battery-powered data loggers to do just that.

“There’s nothing natural about the San Joaquin River,” said Jeremy Hanlon, field team leader with the Environmental Engineering Research Program at the University of the Pacific in Stockton. The group works on grant-based research projects focused on surface water quality in the San Joaquin River and its watershed.

One project in particular, involved monitoring agricultural holding ponds along the river. These farm ponds hold irrigation and runoff water, and serve to trap sediments. In particular, the researcher team was interested in learning how the ponds affect the health of the river, and whether or not they help in treating water as it flows back into the natural system.

To make these determinations, Hanlon and his team have been using a set of battery-operated water level loggers. Costing approximately one-eighth of the team’s previous logging system, the pressure-based water level recording devices are accurate to within 0.1 percent of full-scale accuracy. The loggers are used to calculate the flow of water over the pond’s sharp-crested weir control structure, a crucial baseline measurement for this study.

For a month, Hanlon deployed the new loggers beside his old water level loggers. He constructed stilling wells out of PVC pipe, suspended the loggers within the pipe, and set them up near the pond’s outlet. The loggers were configured to take readings every 15 minutes.

Hanlon goes into the field every two to four weeks to download the data with a portable data shuttle provided by the same manufacturer as the new loggers, Onset Computer Corp., Bourne, Mass. According to Hanlon, data from the new system is as reliable as that from the old system.

He also used the company’s software to analyze and plot water level data, a well as a weather station with wind speed and direction sensors. The system is being used to investigate whether wind may affect a pond’s sediment-filtering ability.

Hanlon and his co-investigators hope to set up more loggers in additional field locations, which, he believes, would translate to more data and better remediation policies. PE