| The Niagara River is the principal outlet for Lake Erie and the Upper Great Lakes Drainage Basin. Its discharge of 200,000 cfs is about the same as the base flow discharge of the Mississippi River at New Orleans. Previous work in the Niagara River by GLC researchers showed that there is a pronounced lateral temperature gradient across the river despite the fact that the water column in the river is thoroughly mixed vertically. The work suggests that the interplay of (1) flow constriction, both laterally and vertically, (2) stratification of the water column in the lake, and especially (3) Coriolus forces, may somehow force lateral flow partitioning. This phenomenon has not previously been described, much less explained. The GLC has undertaken a research program that will provide the preliminary data to choose between the most likely explanations. These two are: |  |
- The distribution may be the result of “flow stripping” and Coriolus force. Water in Lake Erie is normally stratified in the summer with warmer waters near the surface overlying cooler, denser waters. As this stratified water mass approaches the head of the Niagara River, it encounters the progressively shoaling lake bottom so that the cooler water at depth is prevented from flow into the channel, but the warmer water is allowed to pass. At this point, Coriolus forces could force warmer, buoyant waters to the U.S. shore. A compensatory flow of cooler water toward the surface along the Canadian shore would take place so that the whole mass then becomes laterally partitioned. Preliminary calculations of the Burger number suggests that this scenario is possible.
- The distribution may be the result of lateral segregation of temperatures in Lake Erie itself due to upwelling. Winds that blow across Lake Erie from the north during a storm pile up warmer waters along the southern shore, producing a superelevation that results in coastal downwelling. A compensatory upwelling of colder bottom waters occurs offshore, again producing a water mass that would enter the Niagara River as a laterally partitioned field.
A third hypothesis, that the segregation is simply due to warm water flowing from the Buffalo River, has already been rejected based on our previous research because (1) we have tracked the flow from the river into the Black Rock Canal, not the Niagara River; and (2) the warm water flow from the Buffalo River is volumetrically insignificant when compared to that of the Niagara.
Four cruises will be made in the summers of 2005 and 2006 to collect data that will help determine the nature of the hydraulic fractionation in the river. Data in Niagara River near its head, and to a distance of 20 km into Lake Erie will be collected. The data will consist of results from (1) CTD profiling which will give us detailed 3-dimensional models of the temperature, turbidity, conductivity, dissolved oxygen, and pH distributions, and (2) current meter observations which will give us vector information on the velocity field.
