Water level loggers assess impact of holding ponds on river

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BOURNE, MA, Nov. 7, 2007 -- 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 one scientist is using battery-powered data loggers to do just that.

"There's nothing natural about the San Joaquin River," says Jeremy Hanlon, field team leader with the Environmental Engineering Research Program (EERP) 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, involves monitoring agricultural holding ponds along the river. These farm ponds hold irrigation and runoff water, and serve to trap out sediment. In particular, the researcher team is 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 rely on HOBO® Water Level Loggers manufactured by Massachusetts-based Onset.

These loggers, which cost approximately one-eighth of the team's previous logging solution, are pressure-based water level recording devices that offer research-grade accuracy and durability, and provide 0.1% of full-scale accuracy and better than 0.01' resolution. Specifically, 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.

Hanlon purchased several HOBO Water Level Loggers and deployed them side-by-side for a month with the existing water level loggers. The readings were spot-on, and Hanlon was delighted to have found a new, much less expensive water level logging solution.

According to Hanlon, not only are the devices reliable, they're simple to use and deploy. The original water level loggers were large and cumbersome, and involved separate power sources and their own concrete structures.

To deploy the HOBO loggers, Hanlon simply constructed stilling wells out of PVC pipe, suspended the loggers within the pipe, and set them up near the pond's outlet. He configured the loggers to take readings every fifteen minutes, and goes out into the field every two to four weeks to download the data with Onset's portable data shuttle. The shuttle is waterproof and allows for safe data download without the user having to bring a laptop out into the field or the loggers back to the lab.

To analyze and plot water level data, Hanlon uses Onset's HOBOware® Pro graphing and analysis software. The software provides a user-friendly graphical user interface, and offers a number of convenient features such as easy pressure-to-level conversion, and a Barometric Compensation Assistant which automatically compensates for barometric pressure changes.

Hanlon is very happy with the loggers, and expects to use more in the future. EERP also set up a HOBO Micro Station, also made by Onset, with wind speed and direction sensors. The system is being used to investigate whether wind may affect a pond's sediment-filtering ability.

The loggers' relative low cost and portability mean that Hanlon and his co-investigators will be able to set up more loggers in additional field locations, which translates to more data, and hopefully, better remediation policies.

Onset Computer Corporation has been producing small, inexpensive, battery-powered data loggers and embedded controllers since 1981, and has sold over 1,000,000 loggers that are used throughout the world by over 50,000 customers.

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