Navigational Dredging Causes Dissolved Oxygen Problems in Great Lakes Tributaries!
Ann Arbor, MI — Most Great Lakes tributaries are dredged to approximately 30 feet in the lower several miles to permit commercial navigation to port areas within the tributary. It is this physical alteration that has been shown to lead to low dissolved oxygen levels in the bottom waters of these dredged channels.
A collaboration between engineers from Limno-Tech, Inc. and the University at Buffalo developed and applied a numerical model to the lower five miles of the Black River in Ohio specifically aimed at predicting the effect of navigational dredging in the lower three miles of the river on low dissolved oxygen problems in that part of the system. The modeling work demonstrated that the thermal stratification caused by warm water from the watershed colliding with colder water moving into the river from Lake Erie created a hydraulic condition that kept the bottom water from flushing quickly into the lake as well as isolating it from oxygen dissolving into the water from the air above. The resulting condition allowed oxygen in the bottom water to be used by organic matter in the sediments and overlying water faster than it could be replaced from above, thus leading to oxygen concentrations in the lower water of this part of the tributary that were well below the 4 mg/L required for a healthy warm water fish community.
Joe DePinto, one of the study leaders, states: "The Black River that enters Lake Erie at Lorain, OH is only one of many Great Lakes tributaries that are suffering from low dissolved oxygen conditions that result from the physical and hydraulic alterations associated with navigational dredging. We have found almost the identical situation in the lower Buffalo River. Our model has shown that these systems can suffer from low dissolved oxygen conditions even when wastewater discharges into the river are virtually eliminated."
Original Publication Information
Results of this study "Modeling Dissolved Oxygen in a Dredged Lake Erie Tributary," are reported by Jagjit Kaur, Gopi Jaligama, Joseph F. Atkinson, Joseph V. DePinto and Adrienne D. Nemura in the latest issue (Volume 33, No. 1, pp. 62-82) of the Journal of Great Lakes Research, published by the International Association for Great Lakes Research, 2007.
Contacts
For more information about the study, contact Joseph V. DePinto, Senior Scientist, Limno-Tech, Inc., 501 Avis Drive, Ann Arbor, MI 48108; jdepinto@Limno.com; (734)332-1200.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; editor@iaglr.org; (608) 692-1076.
Links
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.